Sun Microsystems, Inc. FORTRAN 77 4.0 Programming Language Compiler Reference Manual
Below you will find brief information for FORTRAN 77 4.0. This document serves as a comprehensive reference manual for the Sun Microsystems FORTRAN 77 4.0 compiler, providing in-depth details on the FORTRAN 77 programming language. It covers fundamental elements such as character sets, symbolic names, and statement formats, progresses through data types, variables, arrays, and complex expressions. It also extensively details various statements, input/output operations, intrinsic functions, and includes specifics on library routines and VMS language extensions, enabling users to effectively develop and manage FORTRAN programs.
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FORTRAN 77 4.0 Reference Manual
A Sun Microsystems, Inc. Business
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Mountain View, CA 94043
U.S.A.
Part No.: 802-2998-10
Revision A, November 1995
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Recycle
1995 Sun Microsystems, Inc. 2550 Garcia Avenue, Mountain View, California 94043-1100 U.S.A.
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®
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Some of the material in this manual is based on the Bell Laboratories document entitled “A Portable Fortran 77 Compiler,” by S. I. Feldman and P. J. Weinberger, dated August 1, 1978. Material on the I/O Library is derived from the paper entitled “Introduction to the f77 I/O
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iii
Contents
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiii
1. Elements of FORTRAN 77 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
1.1 Operating Environments . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3 Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
2
2
1.4 Basic Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.5 Character Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.6 Symbolic Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.7 Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.8 Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Executable or Nonexecutable Statements . . . . . . . . . . . . . . . .
FORTRAN 77 Statements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.9 Source Line Formats. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Standard Fixed Format. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tab-Format. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8
8
7
7
8
9
5
7
2
3
FORTRAN 77 Reference Manual
iv
Mixing Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Continuation Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Extended Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9
Padding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10
9
9
Comments and Blank Lines. . . . . . . . . . . . . . . . . . . . . . . . . . . .
10
Directives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11
2. Data Types and Data Items . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13
2.1 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13
Rules for Data Typing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14
Array Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14
Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14
Properties of Data Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16
2.2 Constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
25
Character Constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26
Complex Constants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28
COMPLEX*16
Constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29
COMPLEX*32
(Quad Complex) Constants . . . . . . . . . . . . . . .
29
Integer Constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30
Logical Constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
31
Real Constants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
32
REAL*8
(Double-Precision Real) Constants . . . . . . . . . . . . . .
33
REAL*16
(Quad Real) Constants . . . . . . . . . . . . . . . . . . . . . . .
34
Typeless Constants (Binary, Octal, Hexadecimal). . . . . . . . . .
35
2.3 Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
39
FORTRAN 77 Reference Manual
2.4 Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
40
Array Declarators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
40
Array Names with No Subscripts. . . . . . . . . . . . . . . . . . . . . . .
43
Array Subscripts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
44
Array Ordering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
45
2.5 Substrings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
46
2.6 Structures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
48
Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
49
Field Declaration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
49
Rules and Restrictions for Structures . . . . . . . . . . . . . . . . . . . .
50
Rules and Restrictions for Fields . . . . . . . . . . . . . . . . . . . . . . .
50
Record Declaration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
51
Record and Field Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . .
52
Substructure Declaration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
54
Unions and Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
56
2.7 Pointers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
58
Syntax Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
58
Usage of Pointers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
58
Address and Memory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
59
Optimization and Pointers . . . . . . . . . . . . . . . . . . . . . . . . . . . .
61
3. Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
65
3.1 Expressions, Operators, and Operands . . . . . . . . . . . . . . .
65
3.2 Arithmetic Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . .
66
Basic Arithmetic Expressions . . . . . . . . . . . . . . . . . . . . . . . . . .
67
Contents
v
vi
Mixed Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
70
Arithmetic Assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
72
3.3 Character Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
74
Character String Assignment . . . . . . . . . . . . . . . . . . . . . . . . . .
76
Rules of Assignment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
78
3.4 Logical Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
78
3.5 Relational Operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
80
3.6 Constant Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
81
3.7 Record Assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
82
3.8 Evaluation of Expressions . . . . . . . . . . . . . . . . . . . . . . . . . .
83
4. Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
85
4.1
ACCEPT
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
85
4.2
ASSIGN
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
86
4.3 Assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
87
4.4
AUTOMATIC
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
93
4.5
BACKSPACE
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
95
4.6
BLOCK DATA
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
97
4.7
BYTE
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
98
4.8
CALL
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
99
4.9
CHARACTER
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
102
4.10
CLOSE
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
105
4.11
COMMON
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
108
4.12
COMPLEX
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
110
4.13
CONTINUE
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
113
FORTRAN 77 Reference Manual
4.14
DATA
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
114
4.15
DECODE
/
ENCODE
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
117
4.16
DIMENSION
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
119
4.17
DO
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
122
4.18
DO WHILE
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
127
4.19
DOUBLE COMPLEX
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
130
4.20
DOUBLE PRECISION
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
131
4.21
ELSE
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
133
4.22
ELSE IF
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
134
4.23
ENCODE
/
DECODE
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
136
4.24
END
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
137
4.25
END DO
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
138
4.26
END FILE
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
139
4.27
END IF
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
141
4.28
END MAP
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
142
4.29
END STRUCTURE
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
142
4.30
END UNION
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
143
4.31
ENTRY
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
144
4.32
EQUIVALENCE
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
147
4.33
EXTERNAL
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
149
4.34
FORMAT
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
151
4.35
FUNCTION
(External) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
155
4.36
GO TO
(Assigned) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
157
4.37
GO TO
(Computed). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
159
Contents
vii
viii
4.38
GO TO
(Unconditional) . . . . . . . . . . . . . . . . . . . . . . . . . . . .
161
4.39
IF
(Arithmetic) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
162
4.40
IF
(Block). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
163
4.41
IF
(Logical) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
166
4.42
IMPLICIT
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
167
4.43
INCLUDE
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
170
4.44
INQUIRE
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
173
4.45
INTEGER
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
179
4.46
INTRINSIC
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
181
4.47
LOGICAL
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
182
4.48
MAP
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
184
4.49
NAMELIST
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
185
4.50
OPEN
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
187
4.51
OPTIONS
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
193
4.52
PARAMETER
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
195
4.53
PAUSE
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
198
4.54
POINTER
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
200
4.55
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
207
4.56
PROGRAM
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
210
4.57
READ
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
211
4.58
REAL
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
217
4.59
RECORD
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
219
4.60
RETURN
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
222
4.61
REWIND
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
223
FORTRAN 77 Reference Manual
4.62
SAVE
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
225
4.63 Statement Function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
226
4.64
STATIC
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
229
4.65
STOP
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
230
4.66
STRUCTURE
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
231
4.67
SUBROUTINE
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
235
4.68
TYPE
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
237
4.69 The Type Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
238
4.70
UNION
and
MAP
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
241
4.71
VIRTUAL
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
243
4.72
VOLATILE
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
243
4.73
WRITE
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
244
5. Input and Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
251
5.1 General Concepts of FORTRAN 77 I/O . . . . . . . . . . . . . .
251
Logical Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
252
I/O Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
252
General Restriction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
253
Kinds of I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
253
Combinations of I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
253
Printing Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
255
Scratch Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
256
Changing I/O Initialization with
IOINIT
. . . . . . . . . . . . . . . .
257
5.2 Direct Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
259
Unformatted I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
259
Contents
ix
x
Formatted I/O. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
260
5.3 Internal Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
260
Sequential Formatted I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
260
Direct Access I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
261
5.4 Formatted I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
261
Input Actions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
261
Output Actions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
262
Format Specifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
263
Runtime Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
296
Variable Format Expressions (
<
e
>
) . . . . . . . . . . . . . . . . . . . . . .
297
5.5 Unformatted I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
298
Sequential Access I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
299
Direct Access I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
299
5.6 List-Directed I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
301
Output Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
302
Unquoted Strings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
304
Internal I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
305
5.7
NAMELIST
I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
305
Syntax Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
305
Restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
306
Output Actions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
306
Input Actions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
308
Data Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
309
Name Requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
313
FORTRAN 77 Reference Manual
6. Intrinsic Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
315
6.1 Arithmetic and Mathematical Functions . . . . . . . . . . . . . .
315
Arithmetic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
316
Type Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
318
Trigonometric Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
320
Other Mathematical Functions . . . . . . . . . . . . . . . . . . . . . . . . .
322
6.2 Character Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
324
6.3 Miscellaneous Functions . . . . . . . . . . . . . . . . . . . . . . . . . . .
325
Bit Manipulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
325
Environmental Inquiry Functions. . . . . . . . . . . . . . . . . . . . . . .
326
Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
327
6.4 Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
327
6.5 Notes on Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
328
6.6 VMS Intrinsic Functions . . . . . . . . . . . . . . . . . . . . . . . . . . .
332
Double-Precision Complex . . . . . . . . . . . . . . . . . . . . . . . . . . . .
333
Degree-Based Trigonometric . . . . . . . . . . . . . . . . . . . . . . . . . . .
333
Bit-Manipulation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
334
Multiple Integer Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
335
Functions Coerced to a Particular Type . . . . . . . . . . . . . . . . . .
336
Functions Translated to a Generic Name . . . . . . . . . . . . . . . . .
337
Zero Extend . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
338
7. FORTRAN 77 Library Routines . . . . . . . . . . . . . . . . . . . . . . . . .
339
7.1
abort
: Terminate and Write Memory to Core File . . . . .
339
7.2
access
: Check File for Permissions or Existence . . . . . .
339
Contents
xi
xii
7.3
alarm
: Execute a Subroutine after a Specified Time . . . .
340
7.4
bit
: Bit Functions:
and
,
or
, …,
bit
,
setbit
, … . . . . . .
342
Usage:
and
,
or
,
xor
,
not
,
rshift
,
lshift
. . . . . . . . . . . . . .
343
Usage:
bic
,
bis
,
bit
,
setbit
. . . . . . . . . . . . . . . . . . . . . . . . .
344
7.5
chdir
: Change Default Directory . . . . . . . . . . . . . . . . . . .
345
7.6
chmod
: Change the Mode of a File . . . . . . . . . . . . . . . . . . .
346
7.7
date
: Get Current System Date as a Character String . .
347
7.8
dtime
,
etime
: Elapsed Execution Time . . . . . . . . . . . . . .
347
dtime
: Elapsed Time Since the Last
dtime
Call . . . . . . . . . .
347
etime
: Elapsed Time Since Start of Execution . . . . . . . . . . . .
348
7.9
exit
: Terminate a Process and Set the Status. . . . . . . . . .
350
7.10
f77_floatingpoint
: FORTRAN 77 IEEE Definitions .
350
IEEE Rounding Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
351
SIGFPE Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
351
IEEE Exception Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
352
IEEE Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
352
7.11
f77_ieee_environment
: IEEE Arithmetic . . . . . . . . . .
353
7.12
fdate
: Return Date and Time in an ASCII String . . . . . .
355
7.13
flush
: Flush Output to a Logical Unit . . . . . . . . . . . . . . .
356
7.14
fork
: Create a Copy of the Current Process . . . . . . . . . . .
357
7.15
free
: Deallocate Memory Allocated by Malloc . . . . . . . .
357
7.16
fseek
,
ftell
: Determine Position and Reposition a File 358
fseek
: Reposition a File on a Logical Unit . . . . . . . . . . . . . . .
358
ftell
: Return Current Position of File . . . . . . . . . . . . . . . . . .
359
FORTRAN 77 Reference Manual
7.17
getarg
,
iargc
: Get Command-line Arguments. . . . . . .
360
getarg
: Get the kth Command-Line Argument . . . . . . . . . .
360
iargc
: Get the Count of Command-Line Arguments . . . . . .
360
7.18
getc
,
fgetc
: Get Next Character . . . . . . . . . . . . . . . . . . .
361
getc
: Get Next Character from
stdin
. . . . . . . . . . . . . . . . . .
361
fgetc
: Get Next Character from Specified Logical Unit. . . .
362
7.19
getcwd
: Get Path of Current Working Directory. . . . . . .
363
7.20
getenv
: Get Value of Environment Variables . . . . . . . . .
364
7.21
getfd
: Get File Descriptor for External Unit Number . .
364
7.22
getfilep
: Get File Pointer for External Unit Number .
365
7.23
getlog
: Get User’s Login Name . . . . . . . . . . . . . . . . . . . .
366
7.24
getpid
: Get Process ID . . . . . . . . . . . . . . . . . . . . . . . . . . . .
367
7.25
getuid
,
getgid
: Get User or Group ID of Process . . . .
367
getuid
: Get User ID of the Process . . . . . . . . . . . . . . . . . . . . .
367
getgid
: Get Group ID of the Process . . . . . . . . . . . . . . . . . . .
368
7.26
hostnm
: Get Name of Current Host . . . . . . . . . . . . . . . . .
368
7.27
idate
: Return Current System Date . . . . . . . . . . . . . . . . .
369
Standard Version. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
369
VMS Version . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
370
7.28
itime
: Current System Time . . . . . . . . . . . . . . . . . . . . . . .
370
7.29
index
: Index or Length of Substring. . . . . . . . . . . . . . . . .
371
index
: First Occurrence of String a2 in String a1. . . . . . . . . .
371
rindex
: Last Occurrence of String a2 in String a1. . . . . . . . .
372
lnblnk
: Last Nonblank in String a1 . . . . . . . . . . . . . . . . . . . .
372
Contents
xiii
xiv
len
: Declared Length of String a1 . . . . . . . . . . . . . . . . . . . . . .
372
7.30
inmax
: Return Maximum Positive Integer . . . . . . . . . . . .
373
7.31
ioinit
: Initialize I/O: Carriage Control, File Names, … 374
Duration of File I/O Properties. . . . . . . . . . . . . . . . . . . . . . . . .
374
Internal Flags. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
374
Source Code. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
375
Usage:
ioinit
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
375
Restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
375
Details of Arguments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
375
7.32
kill
: Send a Signal to a Process . . . . . . . . . . . . . . . . . . . .
378
7.33
libm_double
:
libm
Double-Precision Functions . . . . .
379
Intrinsic Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
379
Non-Intrinsic Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
380
7.34
libm_quadruple
:
libm
Quad-Precision Functions . . .
383
Intrinsic Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
383
Non-Intrinsic Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
383
7.35
libm_single
:
libm
Single-Precision Functions . . . . . .
385
Intrinsic Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
385
Non-Intrinsic Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
385
7.36
link
,
symlnk
: Make a Link to an Existing File . . . . . . . .
388
link:
Create a Link to an Existing File. . . . . . . . . . . . . . . . . .
389
symlnk:
Create a Symbolic Link to an Existing File . . . . . .
389
7.37
loc
: Return the Address of an Object . . . . . . . . . . . . . . . .
390
7.38
long
,
short
: Integer Object Conversion . . . . . . . . . . . . .
390
FORTRAN 77 Reference Manual
long
: Convert a Short Integer to a Long Integer . . . . . . . . . .
390
short
: Convert a Long Integer to a Short Integer . . . . . . . . .
390
7.39
longjmp
,
isetjmp
: Return to Location Set by
isetjmp
391
isetjmp
: Set the Location for
longjmp
. . . . . . . . . . . . . . . . .
391
longjmp
: Return to the location set by
isetjmp
. . . . . . . . .
392
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
392
Restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
393
7.40
malloc
: Allocate Memory and Get Address . . . . . . . . . .
394
7.41
mvbits
: Move a Bit Field . . . . . . . . . . . . . . . . . . . . . . . . . .
395
7.42
perror
,
gerror
,
ierrno
: Get System Error Messages .
396
perror
: Print Message to Logical Unit 0,
stderr
. . . . . . . .
396
gerror
: Get Message for Last Detected System Error . . . . .
396
ierrno
: Get Number for Last Detected System Error . . . . .
397
f77
I/O Error Codes and Meanings . . . . . . . . . . . . . . . . . . . .
398
7.43
putc
,
fputc
: Write a Character to a Logical Unit . . . . . .
399
putc
: Write to Logical Unit 6 . . . . . . . . . . . . . . . . . . . . . . . . . .
399
fputc
: Write to Specified Logical Unit . . . . . . . . . . . . . . . . . .
400
7.44
qsort
: Sort the Elements of a One-dimensional Array .
401
7.45
ran
: Generate a Random Number between 0 and 1 . . . .
402
7.46
rand
,
drand
,
irand
: Return Random Values . . . . . . . . .
403
7.47
rename
: Rename a File . . . . . . . . . . . . . . . . . . . . . . . . . . . .
405
7.48
secnds
: Get System Time in Seconds, Minus Argument 406
7.49
sh
: Fast Execution of an
sh
Command . . . . . . . . . . . . . . .
407
7.50
signal
: Change the Action for a Signal . . . . . . . . . . . . . .
408
Contents
xv
xvi
7.51
sleep
: Suspend Execution for an Interval . . . . . . . . . . . .
409
7.52
stat
,
lstat
,
fstat
: Get File Status . . . . . . . . . . . . . . . .
410
stat
: Get Status for File, by File Name . . . . . . . . . . . . . . . . . .
410
fstat
: Get Status for File, by Logical Unit . . . . . . . . . . . . . . .
411
lstat
: Get Status for File, by File Name. . . . . . . . . . . . . . . . .
411
Detail of Status Array for Files . . . . . . . . . . . . . . . . . . . . . . . . .
412
7.53
system
: Execute a System Command . . . . . . . . . . . . . . . .
413
7.54
time
,
ctime
,
ltime
,
gmtime
: Get System Time . . . . . .
414
time
: Get System Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
414
ctime
: Convert System Time to Character . . . . . . . . . . . . . . .
416
ltime
: Split System Time to Month, Day,… (Local) . . . . . . .
417
gmtime
: Split System Time to Month, Day, … (GMT) . . . . . .
418
7.55
topen
,
tclose
,
tread
,…,
tstate
: Do Tape I/O . . . . .
419
topen
: Associate a Device with a Tape Logical Unit . . . . . . .
419
tclose
: Write EOF, Close Tape Channel, Disconnect tlu . . .
420
twrite
: Write Next Physical Record to Tape . . . . . . . . . . . . .
421
tread
: Read Next Physical Record from Tape . . . . . . . . . . . .
422
trewin
: Rewind Tape to Beginning of First Data File. . . . . .
423
tskipf
: Skip Files and Records; Reset EoF Status. . . . . . . . .
424
tstate
: Get Logical State of Tape I/O Channel . . . . . . . . . .
425
7.56
ttynam
,
isatty
: Get Name of a Terminal Port . . . . . . .
428
ttynam
: Get Name of a Terminal Port. . . . . . . . . . . . . . . . . . .
428
isatty
: Is this Unit a Terminal? . . . . . . . . . . . . . . . . . . . . . . .
429
7.57
unlink
: Remove a File . . . . . . . . . . . . . . . . . . . . . . . . . . . .
429
FORTRAN 77 Reference Manual
7.58
wait
: Wait for a Process to Terminate . . . . . . . . . . . . . . . .
430
8. VMS Language Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
431
8.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
431
8.2 VMS Language Features You Get Automatically . . . . . . .
432
8.3 VMS Language Features that Require
-xl
. . . . . . . . . . . .
436
Summary of Features That Require
-xl[d]
. . . . . . . . . . . . . .
436
Details of Features That Require
-xl[d]
. . . . . . . . . . . . . . . .
437
8.4 Unsupported VMS FORTRAN . . . . . . . . . . . . . . . . . . . . . .
439
A. ASCII Character Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
443
B. Sample Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
447
C. Data Representations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
457
C.1 Real, Double, and Quadruple Precision. . . . . . . . . . . . . . .
457
C.2 Extreme Exponents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
458
Zero (signed) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
458
Subnormal Number . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
458
Signed Infinity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
458
Not a Number (NaN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
458
C.3 IEEE Representation of Selected Numbers . . . . . . . . . . . .
459
C.4 Arithmetic Operations on Extreme Values . . . . . . . . . . . .
459
C.5 Bits and Bytes by Architecture . . . . . . . . . . . . . . . . . . . . . .
462
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
463
Contents
xvii
xviii
FORTRAN 77 Reference Manual
Tables
Table 2-4
Table 2-5
Table 3-1
Table 3-2
Table 3-3
Table 3-4
Table 3-5
Table 3-6
Table 1-1
Table 1-2
Table 1-3
Table 1-4
Table 1-5
Table 2-1
Table 2-2
Table 2-3
Special Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Special Character Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Items with Symbolic Names . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sample Symbolic Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FORTRAN 77 Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8
Sizes and Alignments without
-dalign
,
–f
,
–i2
,
–r8
, or
-dbl
23
Sizes and Alignments Changed by
-i2
. . . . . . . . . . . . . . . . . . .
24
Sizes and Alignments Changed by
-r8
or
-dbl
(SPARC only) 24
5
6
3
4
Sizes and Alignments Changed by
-dalign
or
-f
(SPARC only) 25
Backslash Escape Sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28
Arithmetic Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Arithmetic Expressions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
66
67
Arithmetic Operator Precedence. . . . . . . . . . . . . . . . . . . . . . . . .
Logical Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Logical Operator Precedence . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operator Precedence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
68
78
79
79 xix
xx
Table 5-1
Table 5-2
Table 5-3
Table 5-4
Table 5-5
Table 5-6
Table 5-7
Table 5-8
Table 3-7
Table 3-8
Table 4-1
Table 4-2
Table 4-3
Table 4-4
Table 4-5
Table 4-6
Table 6-1
Table 6-2
Table 6-3
Table 6-4
Table 6-5
Table 6-6
Table 6-7
Table 6-8
Table 6-9
Logical Expressions and Their Meanings . . . . . . . . . . . . . . . . .
Relational Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
79
80
Arithmetic Assignment Conversion Rules . . . . . . . . . . . . . . . .
88
INQUIRE
Options Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . .
177
Intrinsics That Cannot Be Passed As Actual Arguments . . . .
182
OPEN
Keyword Specifier Summary . . . . . . . . . . . . . . . . . . . . . .
187
OPEN
Keyword Specifier Details . . . . . . . . . . . . . . . . . . . . . . . . .
188
OPTIONS
Statement Qualifiers . . . . . . . . . . . . . . . . . . . . . . . . . .
193
Summary of f77
Input and Output . . . . . . . . . . . . . . . . . . . . . .
254
Format Specifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
263
Default w, d, e Values in Format Field Descriptors. . . . . . . . . .
265
Carriage Control with Blank,
0
,
1
, and
+
. . . . . . . . . . . . . . . . . .
268
Maximum Characters in Noncharacter Type Hollerith (nHaaa) 272
Sample Octal/Hex Input Values . . . . . . . . . . . . . . . . . . . . . . . . .
277
Sample Octal/Hex Output Value . . . . . . . . . . . . . . . . . . . . . . . .
278
Default Formats for List-Directed Output . . . . . . . . . . . . . . . . .
304
Arithmetic Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
316
More Arithmetic Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
316
Type Conversion Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
318
Trigonometric Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
320
Other Mathematical Functions . . . . . . . . . . . . . . . . . . . . . . . . . .
322
Character Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
324
Bitwise Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
325
Environmental Inquiry Functions. . . . . . . . . . . . . . . . . . . . . . . .
326
Memory Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
327
FORTRAN 77 Reference Manual
Table 7-2
Table 7-3
Table A-1
Table A-2
Table B-1
Table C-1
Table C-2
Table C-3
Table 6-10 Double-Precision Complex Functions . . . . . . . . . . . . . . . . . . . .
333
Table 6-11 Degree-Based Trigonometric Functions. . . . . . . . . . . . . . . . . . .
333
Table 6-12 Bit-Manipulation Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
334
Table 6-13 Integer Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
335
Table 6-14 Translated Functions that VMS Coerces to a Particular Type 336
Table 6-15 VMS Functions That Are Translated into f77
Generic Names 337
Table 6-16 Zero-Extend Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
338
Table 7-1
DOUBLE PRECISION libm
Functions . . . . . . . . . . . . . . . . . . . .
380
Quadruple-Precision
Single-Precision libm libm
Functions . . . . . . . . . . . . . . . . . . . .
Functions. . . . . . . . . . . . . . . . . . . . . . . . .
ASCII Character Set. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Control Characters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FORTRAN 77 Statement Samples . . . . . . . . . . . . . . . . . . . . . . . .
Floating-point Representation . . . . . . . . . . . . . . . . . . . . . . . . . . .
IEEE Representation of Selected Numbers . . . . . . . . . . . . . . . .
Extreme Value Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . .
384
386
444
445
448
458
459
460
Table C-4
Table C-5
Table C-6
Table C-7
Table C-8
Table C-9
Extreme Values: Addition and Subtraction . . . . . . . . . . . . . . . .
460
Extreme Values: Multiplication . . . . . . . . . . . . . . . . . . . . . . . . . .
460
Extreme Values: Division . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
461
Extreme Values: Comparison . . . . . . . . . . . . . . . . . . . . . . . . . . .
461
Bits and Bytes for Intel and VAX Computers . . . . . . . . . . . . . .
462
Bits and Bytes for 680x0 and SPARC Computers . . . . . . . . . . .
462
Tables
xxi
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FORTRAN 77 Reference Manual
Preface
This preface is organized into the following sections:
Purpose and Audience
How this Book is Organized
Related Manuals
Conventions in Text page xxiii page xxiv page xxiv page xxiv
Purpose and Audience
This manual describes the language and routines of the FORTRAN 77 4.0
compiler from SunSoft.
This is a reference manual. Though it contains many examples, it is not a tutorial. Its function and purpose are solely to help you find features or routines, not to teach you FORTRAN 77, programming, or programming style.
This book is for scientists and engineers with the following background:
•
Thorough knowledge and experience with FORTRAN 77 programming
•
General knowledge and understanding of some operating system
•
Particular knowledge of Solaris
®
or UNIX commands.
For help using the compiler, linker, debugger, the related utilities, or making or using libraries, refer to the FORTRAN 77 4.0 User's Guide.
xxiii
How this Book is Organized
This book is organized as follows:
Chapter 1, Elements of FORTRAN 77
Chapter 2, Data Types and Data Items
Chapter 3, Expressions
Chapter 4, Statements
Chapter 5, Input and Output
Chapter 6, Intrinsic Functions
Chapter 7, FORTRAN 77 Library Routines
Chapter 8, VMS Language Extensions
Appendix A, ASCII Character Set
Appendix B, Sample Statements
Appendix C, Data Representations
Related Manuals
page 1 page 13 page 65 page 85 page 251 page 315 page 339 page 431 page 443 page 447 page 457
The following documents are provided on-line or in hard copy, as indicated:
Title
FORTRAN 77 4.0 User’s Guide
FORTRAN 77 4.0 Reference Manual
Debugging a Program
Incremental Link Editor
Numerical Computation Guide
What Every Computer Scientist Should Know About
Floating-Point Arithmetic
Installing SunSoft Developer Products on Solaris
Hard Copy
X
X
X
X
X
X
On-line
X
X
X
X
X
X
X
Conventions in Text
We use the following conventions in this manual to display information.
xxiv
FORTRAN 77 Reference Manual
•
We show code listings examples in boxes:
WRITE( *, * ) 'Hello world'
•
The plain Courier font
shows prompts and coding.
•
In dialogs, the
boldface Courier font
shows text you type in: demo% echo hello hello demo%
•
Italics indicate general arguments or parameters that you replace with the appropriate input. Italics also indicate emphasis.
•
For Solaris 2.x, the default shell is sh
; the default prompt is the dollar sign
($)
. Most systems have distinct host names, and you can read some of our examples more easily if we use a symbol longer than a dollar sign. Where the csh
shell is shown, we use demo%
as the system prompt.
•
The small clear triangle
∆
shows a blank space where that is significant:
∆∆
36.001
•
We generally tag nonstandard features with a small black diamond (♦). A program that uses a nonstandard feature does not conform to the ANSI
X3.9-1978 standard, as described in American National Standard
Programming Language FORTRAN, ANSI X3.9-1978, April 1978, American
National Standards Institute, Inc., abbreviated as the FORTRAN Standard.
•
We usually show FORTRAN 77 examples in tab format, not fixed columns.
See Section 1.9, “Source Line Formats,” for details.
•
We usually abbreviate FORTRAN 77 as f77
.
xxv
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FORTRAN 77 Reference Manual
Elements of FORTRAN 77
1
This chapter is organized into the following sections.
Operating Environments
Standards
Extensions
Basic Terms
Character Set
Symbolic Names
Program
Statements
Source Line Formats page 1 page 2 page 2 page 2 page 3 page 5 page 7 page 7 page 8
1.1 Operating Environments
Each release of f77
is available first on SPARC systems under the Solaris 2.x
operating environment. For information on other current platforms or operating environments, see the
/READMEs/fortran_77
file.
The previous major release was ported to Solaris™ 1.x and to Intel
®
80386compatible computers running Solaris 2.x for x86, and some features remain in this guide identified as being “Solaris 1.x only” or “x86 only,” and sometimes
“(1.x only)” or “(x86)”.
1
1
1.2 Standards
This FORTRAN 77 compiler is an enhanced FORTRAN 77 development system. It conforms to the ANSI X3.9-1978 FORTRAN 77 standard and the corresponding International Standards Organization number is ISO 1539-1980.
NIST (formerly GSA and NBS) validates it at appropriate intervals.
This compiler also conforms to the standards FIPS 69-1, BS 6832, and MIL-STD-
1753. It provides an IEEE standard 754-1985 floating-point package.
On SPARC systems, it provides support for optimization exploiting features of
SPARC V8, including the SuperSPARC™ implementation. These features are defined in the SPARC Architecture Manual: Version 8.
1.3 Extensions
This FORTRAN 77 compiler provides iMPact™ multiprocessor FORTRAN 77 and lint-like checking across routines for consistency of arguments, commons, parameters, and so forth.
Other extensions include recursion, pointers, double-precision complex, quadruple-precision real, quadruple-precision complex, and many VAX
®
and
VMS
®
FORTRAN 77 5.0 extensions, including
NAMELIST
,
DO WHILE
, structures, records, unions, maps, and variable formats. Multiprocessor
FORTRAN 77 includes automatic and explicit loop parallelization.
You can write FORTRAN 77 programs with many VMS extensions, so that these programs run with the same source code on both SPARC and VAX systems.
2
1.4 Basic Terms
Some of the FORTRAN 77 basic terms and concepts are:
•
A program consists of one or more program units.
•
A program unit is a sequence of statements, terminated by an
END
.
•
A statement consists of zero or more key words, symbolic names, literal constants, statement labels, operators, and special characters.
•
Each key word, symbolic name, literal constant, and operator consists of one or more characters from the FORTRAN 77 character set.
FORTRAN 77 Reference Manual
1
•
A character constant can include any valid ASCII character.
•
A statement label consists of 1 to 5 digits, with at least one nonzero.
1.5 Character Set
The character set consists of the following:
•
Uppercase and lowercase letters, A – Z and a – z
•
Numerals 0 – 9
•
The special characters shown in the following table
Character
<
>
&
\
?
%
!
:
$
_
'
"
Name
Apostrophe
Quote ♦
Dollar sign ♦
Underscore ♦
Exclamation point ♦
Colon
Question mark ♦
Percent ♦
Ampersand ♦
Backslash ♦
Left angle bracket ♦
Right angle bracket ♦
Note the following usage and restrictions:
•
Uppercase and lowercase
—The case is not significant in the key words of
FORTRAN 77 statements or in symbolic names.
The
–U
option of f77
makes case significant in symbolic names. ♦
•
Control characters ♦ —Even though they are not in the character set, most control characters are allowed as data. The exceptions are: Control
A
,
Control
B
, Control C, which are not allowed as data.
While entering a character string, do not hold down the Control key and press the A, B, or C key. Even these characters can be entered other ways, such as with the char()
function.
Elements of FORTRAN 77
3
1
4
•
Special characters
—The following table shows the special characters that are used for punctuation:
Table 1-2
Special Character Usage
Character Usage
Space
Tab
=
+
–
*
/
( )
,
.
'
"
$
!
:
%
&
?
\
< >
Ignored in statements, except as part of a character constant
Establish the line as a tab-format source line ♦
Assignment
Add, unary operator
Subtract, unary operator
Multiply, alternate returns, comments, exponentiation, stdin
, stdout
, list-directed I/O
Divide, delimit data, labeled commons, structures, end-of-record
Enclose expressions, complex constants, equivalence groups, formats, argument lists, subscripts
Separator for data, expressions, complex constants, equivalence groups, formats, argument lists, subscripts
Radix point, delimiter for logical constants and operators, record fields
Quoted character literals
Quoted character literals, octal constants ♦
Delimit namelist input, edit descriptor, directives ♦
Comments ♦
Array declarators, substrings, edit descriptor
Special functions:
%REF
,
%VAL
,
%LOC
♦
Continuation, alternate return, delimit namelist input; in column 1: establish the line as a tab-format source line ♦
Request names in namelist group ♦
Escape character ♦
Enclose variable expressions in formats ♦
FORTRAN 77 Reference Manual
1
•
ASCII characters
—Any ASCII character is valid as literal data in a character string.
♦
For the backslash (\) character, you may need to use an escape sequence or use the
–xl
compiler option. The backslash (\) is also called a reverse solidus, and the slash (/), a solidus. For the newline (\ n
) character, you must use an escape sequence. See also Table 2-5.
1.6 Symbolic Names
The items in the following table can have symbolic names:
Table 1-3
Items with Symbolic Names
Symbolic constants
Variables
Arrays
Structures ♦
Records ♦
Record fields ♦
Labeled commons
Namelist groups ♦
Main programs
Subroutines
Functions
Entry points
The following restrictions apply:
•
Symbolic names can have from 1 to 32 characters. The standard is 6. ♦
•
Symbolic names consist of letters, digits, the dollar sign (
$
), and the underscore character (
_
).
$
and
_
are not standard. ♦
•
Symbolic names generally start with a letter—never with a digit or dollar sign (
$
). Names that start with an underscore (
_
) are allowed, ♦ but it is safer to reserve such names for the compiler.
•
Uppercase and lowercase are not significant; the compiler converts them all to lowercase. The
–U
option on the f77
command line overrides this default, thereby preserving any uppercase used in your source file. ♦
•
Example: These names are equivalent with the default in effect:
ATAD = 1.0E-6
Atad = 1.0e-6
Elements of FORTRAN 77
5
6
1
Consistently separating words by spaces became a general custom about the tenth century
A.D., and lasted until about 1957, when FORTRAN 77 abandoned the practice.
•
The space character is not significant.
Example: These names are equivalent:
IF ( X .LT. ATAD ) GO TO 9
IF ( X .LT. A TAD ) GO TO 9
IF(X.LT.ATAD)GOTO9
Here are some sample symbolic names:
Table 1-4
Sample Symbolic Names
Valid
X2
DELTA_TEMP
Y$Dot
Invalid
2X
_DELTA_TEMP
Y|Dot
Reason
Starts with a digit.
Starts with an
_
(reserved for the compiler).
There is an invalid character
|
.
•
In general, for any single program unit, different entities cannot have the same symbolic name. The exceptions are:
•
A variable or array can have the same name as a common block.
•
A field of a record can have the same name as a structure. ♦
•
A field of a record can have the same name as a field at a different level of the structure. ♦
•
Throughout any program of more than one programming unit, no two of the following can have the same name:
•
Block data subprograms
•
Common blocks
•
Entry points
•
Function subprograms
•
Main program
•
Subroutines
FORTRAN 77 Reference Manual
1
1.7 Program
A program unit is a sequence of statements, terminated by an
END
statement.
Every program unit is either a main program or a subprogram. If a program is to be executable, it must have a main program.
There are three types of subprograms: subroutines, functions, and block data subprograms. The subroutines and functions are called procedures, which are invoked from other procedures or from the main program. The block data subprograms are handled by the loader.
1.8 Statements
A statement consists of one or more key words, symbolic names, literal constants, and operators, with appropriate punctuation. In FORTRAN 77, no keywords are reserved in all contexts. Most statements begin with a keyword; the exceptions are the statement function and assignment statements.
Executable or Nonexecutable Statements
Every statement is either executable or nonexecutable. In general, if a statement specifies an action to be taken at runtime, it is executable. Otherwise, it is nonexecutable.
The nonexecutable statements specify attributes, such as type and size; determine arrangement or order; define initial data values; specify editing instructions; define statement functions; classify program units; and define entry points. In general, nonexecutable statements are completed before execution of the first executable statement.
Elements of FORTRAN 77
7
8
1
FORTRAN 77 Statements
The asterisk (*) indicates an executable statement.
ACCEPT*
ASSIGN*
Assignment
*
AUTOMATIC
BACKSPACE*
BLOCK DATA
BYTE
CALL*
CHARACTER
CLOSE*
COMMON
COMPLEX
CONTINUE*
DATA
DECODE*
DIMENSION
DO*
DO WHILE*
Table 1-5
FORTRAN 77 Statements
DOUBLE COMPLEX
DOUBLE PRECISION
ELSE*
ELSE IF*
ENCODE*
END*
END DO*
END FILE*
END IF*
END MAP
END STRUCTURE
END UNION
ENTRY
EQUIVALENCE
EXTERNAL
FORMAT
FUNCTION
GOTO*
GOTO
(Assigned)
*
GOTO
(Unconditional)
*
IF
(Arithmetic)
*
IF
(Block)
*
IF
(Logical)
*
IMPLICIT
INCLUDE
INQUIRE*
INTEGER
INTRINSIC
LOGICAL
MAP
NAMELIST
OPEN*
OPTIONS
PARAMETER
PAUSE*
POINTER
PRINT*
PRAGMA
PROGRAM
REAL
RECORD
RETURN*
REWIND*
SAVE
Statement Function
STATIC*
STOP*
STRUCTURE
SUBROUTINE*
TYPE
UNION
VIRTUAL
VOLATILE
WRITE*
1.9 Source Line Formats
A statement takes one or more lines; the first line is called the initial line; the subsequent lines are called the continuation lines.
You can format a source line in either of two ways:
•
Standard fixed format
•
Tab format ♦
Standard Fixed Format
The standard fixed format source lines are defined as follows:
•
The first 72 columns of each line are scanned. See “Extended Lines,” page 9.
•
The first five columns must be blank or contain a numeric label.
•
Continuation lines are identified by a nonblank, nonzero in column 6.
•
Short lines are padded to 72 characters.
•
Long lines are truncated. See “Extended Lines,” below.
FORTRAN 77 Reference Manual
1
Tab-Format
The tab-format source lines are defined as follows: ♦
•
A tab in any of columns 1 through 6, or an ampersand in column 1, establishes the line as a tab-format source line.
•
If the tab is the first nonblank character, the text following the tab is scanned as if it started in column 7.
•
A comment indicator or a statement number can precede the tab.
•
Continuation lines are identified by an ampersand (
&
) in column 1, or a nonzero digit after the first tab.
Mixing Formats
You can format lines both ways in one program unit, but not in the same line.
Continuation Lines
The default maximum number of continuation lines is 99 ♦ (1 initial and 99 continuation). To change this number of lines, use the
-Nl
n option. ♦
Extended Lines
To extend the source line length to 132 characters, use the
–e
option.♦
Otherwise, by default, f77
ignores any characters after column 72.
Example: Compile to allow extended lines: demo% f77 -e prog.f
Elements of FORTRAN 77
9
10
1
Padding
Padding is significant in lines such as the two in the following
DATA
statement:
C 1 2 3 4 5 6 7
C23456789012345678901234567890123456789012345678901234567890123456789012
DATA SIXTYH/60H
1 /
Comments and Blank Lines
A line with a c
,
C
,
*
, d
,
D
, or
!
in column one is a comment line, except that if the
–xld
option is set, then the lines starting with
D
or d
are compiled as debug lines. The d
,
D
, and
!
are nonstandard. ♦
If you put an exclamation mark (
!
) in any column of the statement field, except within character literals, then everything after the
!
on that line is a comment.
♦
A totally blank line is a comment line.
Example: c
,
C
, d
,
D
,
*
,
!,
and blank comments: c Start expression analyzer
CHARACTER S, STACK*80
COMMON /PRMS/ N, S, STACK
…
* Crack the expression:
IF ( S .GE. '0' .AND. S .LE. '9' ) THEN ! EoL comment d
CALL PUSH ! Save on stack. EoL comment
PRINT *, S! Debug comment & EoL comment
ELSE
CALL TOLOWER ! To lowercase EoL comment
END IF
D PRINT *, N! Debug comment & EoL comment
…
C Finished
!
expression analyzer
FORTRAN 77 Reference Manual
1
Directives
A directive passes information to a compiler in a special form of comment. ♦
Directives are also called compiler pragmas. There are two kinds of directives:
•
General directives
•
Parallel directives
General Directives
The form of a general directive is one of the following:
•
C$PRAGMA
id
•
C$PRAGMA
id ( a [ , a ] … ) [ , id ( a [ , a ] … ) ] ,…
•
C$PRAGMA sun
id
=
The variable id identifies the kind of directive; a is an argument.
Syntax
A directive has the following syntax:
•
In column one, any of the comment-indicator characters c
,
C
,
!
, or
*
•
In any column, the
!
comment-indicator character
•
The next 7 characters are
$PRAGMA
, no blanks, any uppercase or lowercase
Rules and Restrictions
After the first eight characters, blanks are ignored, and uppercase and lowercase are equivalent, as in FORTRAN 77 text.
Because it is a comment, a directive cannot be continued, but you can have many
C$PRAGMA
lines, one after the other, as needed.
If a comment satisfies the above syntax, it is expected to contain one or more directives recognized by the compiler; if it does not, a warning is issued.
Elements of FORTRAN 77
11
1
12
The
C()
Directive
The
C()
directive specifies that its arguments are external functions written in the C language. It is equivalent to an
EXTERNAL
declaration with the addition that the FORTRAN 77 compiler does not append an underscore to such names, as it ordinarily does with external names.
The
C()
directive for a particular function must appear before the first reference to that function in each subprogram that contains such a reference.
The recommended usage is:
EXTERNAL ABC, XYZ !$PRAGMA C(ABC, XYZ)
The
unroll
Directive
The unroll
directive requires that you specify sun
after
C$PRAGMA
.
The
C$PRAGMA sun unroll=
n directive instructs the optimizer to unroll loops n times, where n is a positive integer. The choices are:
•
If n=1, this directive orders the optimizer not to unroll any loops.
•
If n>1, this directive suggests to the optimizer that it unroll loops n times.
If any loops are actually unrolled, then the executable file becomes larger.
Example: To unroll loops two times:
C$PRAGMA SUN UNROLL=2
Parallel Directives
A parallel directive is a special comment that directs the compiler to do something about parallelization. The following are the parallel directives:
•
DOALL
•
DOSERIAL
•
DOSERIAL*
For syntax and other information on parallel directives, see the appendix on multiple processors in the FORTRAN 77 4.0 User’s Guide.
FORTRAN 77 Reference Manual
2.1 Types
Data Types and Data Items
This chapter is organized into the following sections:
Types
Constants
Variables
Arrays
Substrings
Structures
Pointers page 13 page 25 page 39 page 40 page 46 page 48 page 58
2
Any constant or constant expression usually represents typed data; the exceptions are the typeless constants. Any name of a variable, array, array element, substring, or function usually represents typed data.
The following items have data types:
Constant Expressions
Variables
Arrays
External Functions
Statement Functions
13
2
14
These items do not have data types.
Main Programs
Subroutines
Block Data Subprograms
Common Blocks
Namelist Groups
♦
Structured Records
♦
Rules for Data Typing
The name determines the type; that is, the name of a datum or function determines its data type, explicitly or implicitly, according to the following rules of data typing;
•
A symbolic name of a constant, variable, array, or function has only one data type for each program unit, except for generic functions.
•
If you explicitly list a name in a type statement, then that determines the data type.
•
If you do not explicitly list a name in a type statement, then the first letter of the name determines the data type implicitly.
•
The default implicit typing rule is that if the first letter of the name is
I
,
J
,
K
,
L
,
M
, or
N
, then the data type is integer, otherwise it is real.
•
You can change the default-implied types by using the
IMPLICIT statement, even to the extent of turning off all implicit typing with the
IMPLICIT NONE
statement. You can also turn off all implicit typing by specifying the
–u
compiler flag on the command line; this is equivalent to beginning each program unit with the
IMPLICIT NONE
statement.
Array Elements
An array element has the same type as the array name.
Functions
Each intrinsic function has a specified type. An intrinsic function does not require an explicit type statement, but that is allowed. A generic function does not have a predetermined type; the type is determined by the type of the arguments, as shown in Chapter , “Intrinsic Functions.”
FORTRAN 77 Reference Manual
2
An external function can have its type specified in any of the following ways:
•
Explicitly by putting its name in a type statement
•
Explicitly in its
FUNCTION
statement, by preceding the word
FUNCTION with the name of a data type
•
Implicitly by its name, as with variables
Example: Explicitly by putting its name in a type statement:
FUNCTION F ( X )
INTEGER F, X
F = X + 1
RETURN
END
Example: Explicitly in its
FUNCTION
statement:
INTEGER FUNCTION F ( X )
INTEGER X
F = X + 1
RETURN
END
Example: Implicitly by its name, as with variables:
FUNCTION NXT ( X )
INTEGER X
NXT = X + 1
RETURN
END
Implicit typing can affect the type of a function, either by default implicit typing or by an
IMPLICIT
statement. You must make the data type of the function be the same within the function subprogram as it is in the calling program unit. FORTRAN 77 does no type checking between program units.
Data Types and Data Items
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2
16
Properties of Data Types
This section describes the data types, what each is for, the way storage is allocated for each of them, and the alignment of the different types. Storage and alignment are always given in bytes. Values that can fit into a single byte are byte-aligned.
BYTE
♦
The
BYTE
data type provides a data type that uses only one byte of storage. It is a logical data type, and has the synonym,
LOGICAL*1
.
A variable of type
BYTE
can hold any of the following:
•
One character
•
An integer between -128 and 127
•
The logical values,
.TRUE.
or
.FALSE.
If it is interpreted as a logical value, a value of 0 represents
.FALSE.
, and any other value is interpreted as
.TRUE.
f77
allows the
BYTE
type as an array index, just as it allows the
REAL
type, but it does not allow
BYTE
as a
DO
loop index (where it allows only
INTEGER
,
REAL
, and
DOUBLE PRECISION
). Wherever FORTRAN 77 makes an explicit check for
INTEGER
, it does not allow
BYTE
.
Examples:
&
BYTE Bit3 / 8 /, C1 / 'W' /,
Counter / 0 /, Switch / .FALSE. /
A
BYTE
item occupies 1 byte of storage, and is aligned on 1-byte boundaries.
CHARACTER
The character data type,
CHARACTER
, which has the synonym,
CHARACTER*1
, holds one character.
The character is enclosed in apostrophes (
'
) or quotes (
"
). ♦ Allowing quotes
(") is nonstandard; if you compile with the
–xl
option, quotes mean something else, and you must use apostrophes to enclose a string.
FORTRAN 77 Reference Manual
2
The data of type
CHARACTER
is always unsigned.
A
CHARACTER
item occupies 1 byte (8 bits) of storage.
A
CHARACTER
item is aligned on 1-byte boundaries.
CHARACTER* n
The character string data type,
CHARACTER*
n, where n
> 0
, holds a string of n characters.
A
CHARACTER*
n data type occupies n bytes of storage.
A
CHARACTER*
n variable is aligned on 1-byte boundaries.
Every character string constant is aligned on 2-byte boundaries. If it does not appear in a
DATA
statement, it is followed by a null character to ease communication with C routines.
COMPLEX
A complex datum is an approximation of a complex number. The complex data type,
COMPLEX
, which usually has the synonym
COMPLEX*8
, is a pair of
REAL*4
values that represent a complex number. The first element represents the real part and the second represents the imaginary part.
The usual default size for a
COMPLEX
item (no size specified) is 8. If the
–r8 compiler option is set, then the default size is 16; otherwise, it is 8.
COMPLEX
is aligned on 4-byte boundaries, except if compiled on a Sun-4 or
SPARC computer with the
–f
option, in which case it is aligned on 8-byte boundaries.
COMPLEX*8
♦
The complex data type
COMPLEX*8
is a synonym for
COMPLEX
, except that it always has a size of 8 bytes, independent of any compiler options.
Data Types and Data Items
17
2
18
COMPLEX*16
(Double Complex) ♦
The complex data type
COMPLEX*16
is a synonym for
DOUBLE COMPLEX
, except that it always has a size of 16 bytes, independent of any compiler options.
COMPLEX*32 (
Quad Complex) ♦
(SPARC only) The complex data type
COMPLEX*32
is a quadruple-precision complex. It is a pair of
REAL*16
elements, where each has a sign bit, a 15-bit exponent, and a 112-bit fraction. These
REAL*16
elements in f77
conform to the IEEE standard.
The size for
COMPLEX*32
is 32 bytes.
COMPLEX*32
is aligned on 4-byte boundaries, except if compiled on a Sun-4 or
SPARC computer with the
–f
option, in which case it is aligned on 8-byte boundaries.
DOUBLE COMPLEX
♦
The complex data type,
DOUBLE COMPLEX
, which usually has the synonym,
COMPLEX*16
, is a pair of
DOUBLE PRECISION
(
REAL*8
) values that represents a complex number. The first element represents the real part; the second represents the imaginary part.
The default size for
DOUBLE COMPLEX
with no size specified is 16. If the
–r8 compiler option is set, then the default size is 32; otherwise, it is 16.
COMPLEX*16
is aligned on 4-byte boundaries, except if compiled on a Sun-4 or
SPARC computer with the
–f
option, in which case it is aligned on 8-byte boundaries.
DOUBLE PRECISION
A double-precision datum is an approximation of a real number. The doubleprecision data type,
DOUBLE PRECISION
, which has the synonym,
REAL*8
, holds one double-precision datum.
The default size for
DOUBLE PRECISION
with no size specified is 8. If the
–r8 compiler option is set, then the default size is 16; otherwise, 8.
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2
DOUBLE PRECISION
is aligned on 4-byte boundaries.
A
DOUBLE PRECISION
element has a sign bit, an 11-bit exponent, and a 52-bit fraction. These
DOUBLE PRECISION
elements in f77
conform to the IEEE standard for double-precision floating-point data. The layout is shown in
Appendix C, “Data Representations.”
INTEGER
The integer data type,
INTEGER
, holds a signed integer.
The default size for
INTEGER
with no size specified is 4. However:
•
If the
–i2
compiler option is set, then the default size is 2; otherwise, it is 4.
•
If the
–r8
compiler option is set, then the default size is 8; otherwise, it is 4.
•
If both the
–i2
and
–r8
options are set, then the results are unpredictable.
•
If both the
-r8
and
-dbl
options are set, then the default size is 8, and the values are 64 bits long. Thus,
-dbl
is the only way to set 64-bit integer values.
This data type is aligned on 4-byte boundaries, unless the
–i2
option is set, in which case it is aligned on 2-byte boundaries.
INTEGER*2
♦
The short integer data type,
INTEGER*2
, holds a signed integer. An expression involving only objects of type
INTEGER*2
is of that type. Using this feature may have adverse performance implications, and we do not recommend it.
Generic functions return short or long integers depending on the default integer type. If a procedure is compiled with the
–i2
flag, all integer constants that fit and all variables of type
INTEGER
(no explicit size) are of type
INTEGER*2
. If the precision of an integer-valued intrinsic function is not determined by the generic function rules, one is chosen that returns the prevailing length (
INTEGER*2
) when the
–i2
command flag is in effect. When the
–i2
option is in effect, the default length of
LOGICAL
quantities is 2 bytes.
Ordinary integers follow the FORTRAN 77 rules about occupying the same space as a
REAL
variable. They are assumed to be equivalent to the C type long int
, and 1-byte integers are of C type short int
. These short integer and logical quantities do not obey the standard rules for storage association.
Data Types and Data Items
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20
An
INTEGER*2
occupies 2 bytes.
INTEGER*2
is aligned on 2-byte boundaries.
INTEGER*4
♦
The integer data type,
INTEGER*4
, holds a signed integer.
An
INTEGER*4
occupies 4 bytes.
INTEGER*4
is aligned on 4-byte boundaries.
INTEGER*8
♦
The integer data type,
INTEGER*8
, holds a signed 64-bit integer. It is allowed only if the
-dbl
option is set.
An
INTEGER*8
occupies 8 bytes.
INTEGER*8
is aligned on 8-byte boundaries.
LOGICAL
The logical data type,
LOGICAL
, holds a logical value
.TRUE.
or
.FALSE.
The value 0 represents
.FALSE.
; any other value represents
.TRUE.
The usual default size for an
LOGICAL
item with no size specified is 4.
However:
•
If the
–i2
option is set, then the default size is 2; otherwise, it is 4.
•
If the
–r8
or
-dbl
option is set, then the default size is 8; otherwise, it is 4.
•
If both the
–i2
and
–r8
options are set, then the results are unpredictable.
LOGICAL
is aligned on 4-byte boundaries, unless the
–i2
option is set, then it is aligned on 2-byte boundaries.
If the
–i2
compiler flag is set, then
LOGICAL
(without any size specification) is the same as
LOGICAL*2
; otherwise, it is the same as
LOGICAL*4
.
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2
LOGICAL*1
♦
The one-byte logical data type,
LOGICAL*1
, which has the synonym,
BYTE
, can hold any of the following:
•
One character
•
An integer between -128 and 127
•
The logical values
.TRUE.
or
.FALSE.
The value is as defined for
LOGICAL
, but it can hold a character or small integer. An example:
&
LOGICAL*1 Bit3 / 8 /, C1 / 'W' /,
Counter / 0 /, Switch / .FALSE. /
A
LOGICAL*1
item occupies one byte of storage.
LOGICAL*1
is aligned on one-byte boundaries.
LOGICAL*2
♦
The data type,
LOGICAL*2
, holds logical value
.TRUE.
or
.FALSE.
The value is defined as for
LOGICAL
.
A
LOGICAL*2
occupies 2 bytes.
LOGICAL*2
is aligned on 2-byte boundaries.
LOGICAL*4
♦
The logical data type,
LOGICAL*4
holds a logical value
.TRUE.
or
.FALSE.
The value is defined as for
LOGICAL
.
A
LOGICAL*4
occupies 4 bytes.
LOGICAL*4
is aligned on 4-byte boundaries.
LOGICAL*8
♦
The logical data type,
LOGICAL*8
, holds the logical value
.TRUE.
or
.FALSE.
This data type is allowed only if the
-dbl
option is set. The value is defined the same way as for the
LOGICAL
data type.
Data Types and Data Items
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22
A
LOGICAL*8
occupies 8 bytes.
LOGICAL*8
is aligned on 8-byte boundaries.
REAL
A real datum is an approximation of a real number. The real data type,
REAL
, which usually has the synonym,
REAL*4
, holds one real datum.
The usual default size for a
REAL
item with no size specified is 4 bytes. If the
–r8
option is set, then the default size is 8 bytes; otherwise, it is 4 bytes.
REAL
is aligned on 4-byte boundaries, except if compiled on a Sun-4 or SPARC computer with the
–f
option, in which case it is aligned on 8-byte boundaries.
A
REAL
element has a sign bit, an 8-bit exponent, and a 23-bit fraction. These
REAL
elements in f77
conform to the IEEE standard.
REAL*4
♦
The
REAL*4
data type is a synonym for
REAL
, except that it always has a size of 4 bytes, independent of any compiler options.
REAL*8
(Double-Precision Real) ♦
The
REAL*8
, data type is a synonym for
DOUBLE PRECISION
, except that it always has a size of 8 bytes, independent of any compiler options.
REAL*16
(Quad Real) ♦
(SPARC only) The
REAL*16
data type is a quadruple-precision real.
The size for a
REAL*16
item is 16 bytes.
REAL*16
is aligned on 4-byte boundaries, except if compiled on a Sun-4 or
SPARC computer with the
–f
option, in which case it is aligned on 8-byte boundaries.
A
REAL*16
element has a sign bit, a 15-bit exponent, and a 112-bit fraction.
These
REAL*16
elements in f77
conform to the IEEE standard for extended precision.
FORTRAN 77 Reference Manual
2
Size and Alignment Summary
The size and alignment of types depends on various compiler options. This table summarizes the size and alignment, ignoring other aspects of types and options.
Table 2-1
Sizes and Alignments without
-dalign
,
–f
,
–i2
,
–r8
, or
-dbl
FORTRAN 77 Type
BYTE
CHARACTER
CHARACTER*n
COMPLEX
COMPLEX*8
COMPLEX*16
DOUBLE COMPLEX
COMPLEX*32
(SPARC only)
REAL
Synonyms:
COMPLEX
≡
COMPLEX
*
8
INTEGER
≡
INTEGER*4
LOGICAL
≡
LOGICAL*4
REAL
≡
REAL*4
DOUBLE COMPLEX
≡
COMPLEX*16
DOUBLE PRECISION
≡
REAL*8
REAL*4
REAL*8
DOUBLE PRECISION
REAL*16
(SPARC only)
These are synonyms in the sense that
COMPLEX
is treated the same as
COMPLEX*8
;
INTEGER
is treated the same as
INTEGER*4
, and so forth.
INTEGER
INTEGER*4
INTEGER*2
LOGICAL
REAL*16
is sometimes called quad real.
COMPLEX*32
is sometimes called quad complex.
LOGICAL*4
LOGICAL*2
LOGICAL*1
Size (Bytes)
4
2
16
4
8
8
4
4
2
1
4
4
8
16
16
32 n
8
1
1
Alignment (Bytes)
4
2
4
4
4
4
4
4
2
1
4
4
4
4
4
4
1
4
1
1
-dalign
triggers the
-f
option.
Data Types and Data Items
23
2
Arrays and structures align according to their elements or fields. An array aligns the same as the array element. A structure aligns the same as the field with the widest alignment.
Table 2-2
Sizes and Alignments Changed by
-i2
FORTRAN 77 Type
INTEGER
LOGICAL
Size (Bytes)
2
2
Alignment (Bytes)
2
2
Changed synonyms:
INTEGER
≡
INTEGER*2
LOGICAL
≡
LOGICAL*2
Do not use
–i2
with
–i4
or
–r8
.
Changed synonyms:
COMPLEX
≡
COMPLEX*16
INTEGER
≡
INTEGER*8
LOGICAL
≡
LOGICAL *8
REAL
≡
REAL*8
DOUBLE PRECISION
≡
REAL*16
DOUBLE COMPLEX
≡
COMPLEX*32
Table 2-3
Sizes and Alignments Changed by
-r8
or
-dbl
(SPARC only)
FORTRAN 77 Type
COMPLEX
DOUBLE COMPLEX
REAL
DOUBLE PRECISION
Size (Bytes)
16
32
8
16
Alignment (Bytes)
4
4
4
4
INTEGER
LOGICAL
8
8
4
4
Do not use
–r8
with
–i2
.
With
-dbl
or
-r8
,
INTEGER
and
LOGICAL
are allocated the larger space indicated above. This is done to maintain the FORTRAN 77 requirement that an integer item and a real item have the same amount of storage. However, with
-r8
8 bytes are allocated but only 4-byte arithmetic is done. With
-dbl
,
8 bytes are allocated and full 8-byte arithmetic is done. In all other ways,
-dbl and
-r8
produce the same results.
24
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2
2.2 Constants
Table 2-4
Sizes and Alignments Changed by
-dalign
or
-f
(SPARC only)
FORTRAN 77 Type
COMPLEX*8
COMPLEX*16
DOUBLE COMPLEX
COMPLEX*32
(SPARC only)
REAL*8
REAL*16
(SPARC only)
Size (Bytes)
8
16
16
32
8
16
Alignment (Bytes)
8
8
8
8
8
8
-dalign
triggers the
-f
option.
A constant is a datum whose value cannot change throughout the program unit. The form of the string representing a constant determines the value and data type of the constant.
There are three general kinds of constants:
•
Arithmetic
•
Logical
•
Character
Blank characters within an arithmetic or logical constant do not affect the value of the constant. Within character constants, they do affect the value.
Here are the different kinds of arithmetic constants:
Typed Constants
Complex
Double complex
Double precision
Integer
Real
Typeless Constants
Binary
Octal
Hexadecimal
Hollerith
Data Types and Data Items
25
2
A signed constant is an arithmetic constant with a leading plus or minus sign.
An unsigned constant is an arithmetic constant without a leading sign.
For integer, real, and double-precision data, zero is neither positive nor negative. The value of a signed zero is the same as that of an unsigned zero.
Character Constants
A character-string constant is a string of characters enclosed in apostrophes or quotes. The apostrophes are standard; the quotes are not. ♦
If you compile with the
–xl
option, then the quotes mean something else, and you must use apostrophes to enclose a string.
To include an apostrophe in an apostrophe-delimited string, repeat it. To include a quote in a quote-delimited string, repeat it. Examples:
'abc'
'ain''t'
"abc"
"in vi type ""h9Y"
If a string begins with one kind of delimiter, the other kind can be embedded within it without using the repeated quote or backslash escapes. See Table 2-5.
Example: Character constants:
"abc" "abc"
"ain't" 'in vi type "h9Y'
26
FORTRAN 77 Reference Manual
2
Null Characters
♦
Each character string constant appearing outside a
DATA
statement is followed by a null character to ease communication with C routines. You can make character string constants consisting of no characters, but only as arguments being passed to a subprogram. Such zero length character string constants are not FORTRAN 77 standard.
Example: Null character string: demo% cat NulChr.f write(*,*) 'a', '', 'b' stop end demo% f77 NulChr.f
NulChr.f:
MAIN: demo% a.out ab demo%
However, if you put such a null character constant into a character variable, the variable will contain a blank, and have a length of at least 1 byte.
Example: Length of null character string: demo% cat NulVar.f character*1 x / 'a' /, y / '' /, z / 'c' / write(*,*) x, y, z write(*,*) len( y ) end demo% f77 NulVar.f
NulVar.f:
MAIN: demo% a.out a c
1 demo%
Data Types and Data Items
27
2
Escape Sequences
♦
For compatibility with C usage, the following backslash escapes are recognized. If you include the escape sequence in a character string, then you get the indicated character.
28
If you compile with the
–xl
option, then the backslash character (
\
) is treated as an ordinary character. That is, with the
–xl
option, you cannot use these escape sequences to get special characters.
Technically, the escape sequences are not nonstandard, but are implementationdefined.
Complex Constants
A complex constant is an ordered pair of real or integer constants. The constants are separated by a comma, and the pair is enclosed in parentheses.
The first constant is the real part, and the second is the imaginary part. A complex constant,
COMPLEX*8
, uses 8 bytes of storage.
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Example: Complex constants:
( 9.01, .603 )
( +1.0, -2.0 )
( +1.0, -2 )
( 1, 2 )
( 4.51, )
Invalid —need second part
COMPLEX*16
Constants
A double-complex constant,
COMPLEX*16
, is an ordered pair of real or integer constants, where one of the constants is
REAL*8
, and the other is
INTEGER
,
REAL*4
, or
REAL*8
. ♦
The constants are separated by a comma, and the pair is enclosed in parentheses. The first constant is the real part, and the second is the imaginary part. A double-complex constant,
COMPLEX*16
, uses 16 bytes of storage.
Example: Double-complex constants:
( 9.01D6, .603 )
( +1.0, -2.0D0 )
( 1D0, 2 )
( 4.51D6, )
( +1.0, -2.0 )
Invalid—need second part
Not
DOUBLE COMPLEX
—need a
REAL*8
COMPLEX*32
(Quad Complex) Constants
(SPARC only) A quad complex constant ♦ is an ordered pair of real or integer constants, where one of the constants is
REAL*16
, and the other is
INTEGER
,
REAL*4
,
REAL*8
, or
REAL*16
. ♦
The constants are separated by a comma, and the pair is enclosed in parentheses. The first constant is the real part, and the second is the imaginary part. A quad complex constant,
COMPLEX*32
♦, uses 32 bytes of storage.
Data Types and Data Items
29
2
30
Example: Quad complex constants (SPARC only):
( 9.01Q6, .603 )
( +1.0, -2.0Q0 )
( 1Q0, 2 )
( 3.3Q-4932, 9 )
( 1, 1.1Q+4932 )
( 4.51Q6, )
( +1.0, -2.0 )
Invalid—need second part
Not quad complex —need a
REAL*16
Integer Constants
An integer constant consists of an optional plus or minus sign, followed by a string of decimal digits.
Restrictions
No other characters are allowed except, of course, a space.
If no sign is present, the constant is assumed to be nonnegative.
The value must be in the range (-2147483648, 2147483647).
If the
-dbl
option is set, then the value must be in the range
(-9223372036854775808,9223372036854775807).
Example: Integer constants:
-2147483648
-2147483649
-10
0
+199
29002
2.71828
1E6
29,002
2147483647
2147483648
Invalid—too small, error message
Not
INTEGE
—decimal point not allowed
Not
INTEGER
—
E
not allowed
Invalid—comma not allowed, error message
Invalid— too large, error message
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Alternate Octal Notation ♦
You can also specify integer constants with the following alternate octal notation. Precede an integer string with a double quote (
"
) and compile with the
–xl
option. These are octal constants of type
INTEGER
.
Example: The following two statements are equivalent:
JCOUNT = ICOUNT + "703
JCOUNT = ICOUNT + 451
You can also specify typeless constants as binary, octal, hexadecimal, or
Hollerith. See “Typeless Constants (Binary, Octal, Hexadecimal)” on page 35.
Long Integers ♦
If the
-dbl
option is used, then the range of integer constants is changed from
(-21474836, 21474836) to (-9223372036854775808, 9223372036854775807). The integer constant is stored or passed as an 8-byte integer, data type
INTEGER*8
.
Short Integers ♦
If a constant argument is in the range (-32768, 32767), it is usually widened to a
4-byte integer, data type
INTEGER*4
; but if the
–i2
option is set, then it is stored or passed as a 2-byte integer, data type
INTEGER*2
.
Logical Constants
A logical constant is either the logical value true or false. The only logical constants are
.TRUE.
and
.FALSE.
; no others are possible. The period delimiters are necessary.
A logical constant takes 4 bytes of storage. If it is an actual argument, it is passed as 4 bytes, unless the
–i2
option is set, in which case it is passed as 2.
Data Types and Data Items
31
2
32
Real Constants
A real constant is an approximation of a real number. It can be positive, negative, or zero. It has a decimal point or an exponent. If no sign is present, the constant is assumed to be nonnegative.
Real constants,
REAL*4
, use 4 bytes of storage.
Basic Real Constant
A basic real constant consists of an optional plus or minus sign, followed by an integer part, followed by a decimal point, followed by a fractional part.
The integer part and the fractional part are each strings of digits, and you can omit either of these parts, but not both.
Example: Basic real constants:
+82.
-32.
90.
98.5
Real Exponent
A real exponent consists of the letter
E
, followed by an optional plus or minus sign, followed by an integer.
Example: Real exponents:
E+12
E-3
E6
Real Constant
A real constant has one of these forms:
•
Basic real constant
•
Basic real constant followed by a real exponent
•
Integer constant followed by a real exponent
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A real exponent denotes a power of ten. The value of a real constant is the product of that power of ten and the constant that precedes the
E
.
Example: Real constants:
-32.
-32.18
1.6E-9
7E3
1.6E12
$1.0E2.0
82
29,002.0
1.6E39
1.6E-39
Invalid—
$
not allowed, error message
Not
REAL
—need decimal point or exponent
Invalid —comma not allowed, error message
Invalid—too large, machine infinity is used
Invalid —too small, some precision is lost
The restrictions are:
•
Other than the optional plus or minus sign, a decimal point, the digits 0 through 9, and the letter
E
, no other characters are allowed.
•
The magnitude of a normalized single-precision floating-point value must be in the approximate range (1.175494E-38, 3.402823E+38).
REAL*8
(Double-Precision Real) Constants
A double-precision constant is an approximation of a real number. It can be positive, negative, or zero. If no sign is present, the constant is assumed to be nonnegative. A double-precision constant has a double-precision exponent and an optional decimal point. Double-precision constants,
REAL*8
, use 8 bytes of storage. The
REAL*8
notation is nonstandard. ♦
Double-Precision Exponent
A double-precision exponent consists of the letter
D
, followed by an optional plus or minus sign, followed by an integer.
A double-precision exponent denotes a power of 10. The value of a doubleprecision constant is the product of that power of 10 and the constant that precedes the
D
. The form and interpretation are the same as for a real exponent, except that a
D
is used instead of an
E
.
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34
Examples of double-precision constants are:
1.6D-9
7D3
$1.0D2.0
82
29,002.0D0
1.8D308
1.0D-324
Invalid —
$
not allowed, error message
Not
DOUBLE PRECISION
—need decimal point or exponent
Invalid—comma not allowed, error message
Invalid—too large, machine infinity is used
Invalid—too small, some precision is lost
The restrictions are:
•
Other than the optional plus or minus sign, a decimal point, the digits 0 through 9, a blank, and the letter
D
. No other characters are allowed.
•
The magnitude of an IEEE normalized double-precision floating-point value must be in the approximate range (2.225074D-308, 1.797693D+308).
REAL*16
(Quad Real) Constants
(SPARC only) A quadruple-precision constant is a basic real constant (see the start of the section, “Real Constants” on page 32), or an integer constant, such that it is followed by a quadruple-precision exponent. ♦
A quadruple-precision exponent consists of the letter
Q
, followed by an optional plus or minus sign, followed by an integer.
A quadruple-precision constant can be positive, negative, or zero. If no sign is present, the constant is assumed to be nonnegative.
Example: Quadruple-precision constants (SPARC only):
1.6Q-9
7Q3
3.3Q-4932
1.1Q+4932
$1.0Q2.0
82
29,002.0Q0
1.6Q5000
1.6Q-5000
Invalid—
$
not allowed, error message
Not
quad
—need exponent
Invalid—comma not allowed, error message
Invalid—too large, machine infinity is used
Invalid—too small, some precision is lost
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The form and interpretation are the same as for a real constant, except that a
Q is used instead of an
E
.
The restrictions are:
•
Other than the optional plus or minus sign, a decimal point, the digits 0 through 9, a blank, and the letter
Q
. No other characters are allowed.
•
The magnitude of an IEEE normalized quadruple-precision floating-point value must be in the approximate range (3.362Q-4932, 1.20Q+4932).
•
It occupies 16 bytes of storage.
•
Each such datum is aligned on 4-byte boundaries.
Typeless Constants
(Binary, Octal, Hexadecimal
)
Typeless numeric constants are so named because their expressions assume data types based on how they are used. ♦
These constants are not converted before use. However, in f77
, they must be distinguished from character strings.
The general form is to enclose a string of appropriate digits in apostrophes and prefix it with the letter
B
,
O
,
X
, or
Z
. The
B
is for binary, the
O
is for octal, and the
X
or
Z
are for hexadecimal.
Example: Binary, octal, and hexadecimal constants,
DATA
and
PARAMETER
:
PARAMETER ( P1 = Z'1F' )
INTEGER*2 N1, N2, N3, N4
DATA N1 /B'0011111'/, N2/O'37'/, N3/X'1f'/, N4/Z'1f'/
WRITE ( *, 1 ) N1, N2, N3, N4, P1
1 FORMAT ( 1X, O4, O4, Z4, Z4, Z4 )
END
Note the edit descriptors in
FORMAT
statements:
O
for octal, and
Z
for hexadecimal. Each of the above integer constants has the value 31 decimal.
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36
Example: Binary, octal, and hexadecimal, other than in
DATA
and
PARAMETER
:
INTEGER*4 M, ICOUNT/1/, JCOUNT
REAL*4 TEMP
M = ICOUNT + B'0001000'
JCOUNT = ICOUNT + O'777'
TEMP = X'FFF99A'
WRITE(*,*) M, JCOUNT, TEMP
END
In the above example, the context defines
B'0001000'
and
O'777'
as
INTEGER*4
and
X'FFF99A'
as
REAL*4
. For a real number, using IEEE floating-point, a given bit pattern yields the same value on different architectures.
The above statements are treated as the following:
M = ICOUNT + 8
JCOUNT = ICOUNT + 511
TEMP = 2.35076E-38
Control Characters
You can enter control characters with typeless constants, although the
CHAR function is standard, and this way is not.
Example: Control characters with typeless constants:
CHARACTER BELL, ETX / X'03' /
PARAMETER ( BELL = X'07' )
Alternate Notation for Typeless Constants
For compatibility with other versions of FORTRAN 77, the following alternate notation is allowed for octal and hexadecimal notation. This alternate does not work for binary, nor does it work in
DATA
or
PARAMETER
statements.
For an octal notation, enclose a string of octal digits in apostrophes and append the letter
O
.
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Example: Octal alternate notation for typeless constants:
'37'O
37'O
'37'
'397'O
Invalid—missing initial apostrophe
Not
numeric
— missing letter
O
Invalid—invalid digit
For hexadecimals, enclose a string of hex digits in apostrophes and append the letter
X
.
Example: Hex alternate notation for typeless constants:
'ab'X
3fff'X
'1f'X
'1fX
'3f'
'3g7'X
Invalid—missing trailing apostrophe
Not
numeric
— missing
X
Invalid—invalid digit
g
Here are the rules and restrictions for binary, octal, and hexadecimal constants:
•
These constants are for use anywhere numeric constants are allowed.
•
These constants are typeless. They are stored in the variables without any conversion to match the type of the variable, but they are stored in the appropriate part of the receiving field—low end, high end.
•
If the receiving data type has more digits than are specified in the constant, zeros are filled on the left.
•
If the receiving data type has fewer digits than are specified in the constant, digits are truncated on the left. If nonzero digits are lost, an error message is displayed.
•
Specified leading zeros are ignored.
•
You can specify up to 8 bytes of data for any one constant—at least that's all that are used.
•
If a typeless constant is an actual argument, it has no data type, but it is
always 4 bytes that are passed.
•
For binary constants, each digit must be 0 or 1.
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38
•
For octal constants, each digit must be in the range 0 to 7.
•
For hexadecimal constants, each digit must be in the range 0 to 9 or in the range A to F, or a to f.
•
Outside of
DATA
statements, such constants are treated as the type required by the context. If a typeless constant is used with a binary operator, it gets the data type of the other operand (
8.0 + '37'O
).
•
In
DATA
statements, such constants are treated as typeless binary, hexadecimal, or octal constants.
Hollerith Constants
♦
A Hollerith constant consists of an unsigned, nonzero, integer constant, followed by the letter
H
, followed by a string of printable characters where the integer constant designates the number of characters in the string, including any spaces and tabs.
A Hollerith constant occupies 1 byte of storage for each character.
A Hollerith constant is aligned on 2-byte boundaries.
The FORTRAN 77 standard does not have this old Hollerith notation, although the standard recommends implementing the Hollerith feature to improve compatibility with old programs.
Hollerith data can be used in place of character-string constants. They can also be used in
IF
tests, and to initialize noncharacter variables in
DATA
statements and assignment statements, though none of these are recommended, and none are standard. These are typeless constants.
Example: Typeless constants:
CHARACTER C*1, CODE*2
INTEGER TAG*2
DATA TAG / 2Hok /
CODE = 2Hno
IF ( C .EQ. 1HZ ) CALL PUNT
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2.3 Variables
2
The rules and restrictions on Hollerith constants are:
•
The number of characters has no practical limit.
•
The characters can continue over to a continuation line, but that gets tricky.
Short standard fixed format lines are padded on the right with blanks up to
72 columns, but short tab-format lines stop at the newline.
•
If a Hollerith constant is used with a binary operator, it gets the data type of the other operand.
•
If you assign a Hollerith constant to a variable, and the length of the constant is less than the length of the data type of the variable, then spaces
(ASCII 32) are appended on the right.
If the length of a Hollerith constant or variable is greater than the length of the data type of the variable, then characters are truncated on the right.
•
If a Hollerith constant is used as an actual argument, it is passed as a 4-byte item.
•
If a Hollerith constant is used, and the context does not determine the data type, then
INTEGER*4
is used.
A variable is a symbolic name paired with a storage location. A variable has a name, a value, and a type. Whatever datum is stored in the location is the value of the variable. This does not include arrays, array elements, records, or record fields, so this definition is more restrictive than the usual usage of the word “variable.”
You can specify the type of a variable in a type statement. If the type is not explicitly specified in a type statement, it is implied by the first letter of the variable name: either by the usual default implied typing, or by any implied typing of
IMPLICIT
statements. See Section 2.1, “Types,” for more details on the rules for data typing.
At any given time during the execution of a program, a variable is either
defined or undefined. If a variable has a predictable value, it is defined; otherwise, it is undefined. A previously defined variable may become undefined, as when a subprogram is exited.
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You can define a variable with an assignment statement, an input statement, or a
DATA
statement. If a variable is assigned a value in a
DATA
statement, then it is initially defined.
Two variables are associated if each is associated with the same storage location. You can associate variables by use of
EQUIVALENCE
,
COMMON
, or
MAP statements. Actual and dummy arguments can also associate variables.
2.4 Arrays
An array is a named collection of elements of the same type. It is a nonempty sequence of data and occupies a group of contiguous storage locations. An array has a name, a set of elements, and a type.
An array name is a symbolic name for the whole sequence of data.
An array element is one member of the sequence of data. Each storage location holds one element of the array.
An array element name is an array name qualified by a subscript. See “Array
Subscripts,” on page 14 for details.
You can declare an array in any of the following statements:
•
DIMENSION
statement
•
COMMON
statement
•
Type statements
: BYTE
,
CHARACTER
,
INTEGER
,
REAL
, and so forth
Array Declarators
An array declarator specifies the name and properties of an array.
The syntax of an array declarator is:
a
(
d
[,
d
] … ) where:
•
a
is the name of the array
•
d
is a dimension declarator
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A dimension declarator has the form:
[
dl
:]
du
where:
•
dl is the lower dimension bound
•
du is the upper dimension bound
The number of dimensions in an array is the number of dimension declarators.
The minimum number of dimensions is one; the maximum is seven. For an assumed-size array, the last dimension can be an asterisk.
The lower bound indicates the first element of the dimension, and the upper
bound indicates the last element of the dimension. In a one-dimensional array, these are the first and last elements of the array.
Example: Array declarator, lower and upper bounds:
REAL V(-5:5)
In the above example,
V
is an array of real numbers, with 1 dimension and 11 elements. The first element is
V(-5)
; the last element is
V(5)
.
Example: Default lower bound of 1:
REAL V(1000)
In the above example,
V
is an array of real numbers, with 1 dimension and
1000 elements. The first element is
V(1)
; the last element is
V(1000)
.
Example: Arrays can have as many as 7 dimensions:
REAL TAO(2,2,3,4,5,6,10)
Example: Lower bounds other than one:
REAL A(3:5, 7, 3:5), B(0:2)
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Example: Character arrays:
CHARACTER M(3,4)*7, V(9)*4
The array
M
has 12 elements, each of which consists of 7 characters.
The array
V
has 9 elements, each of which consists of 4 characters.
The following restrictions on bounds apply:
•
Both the upper and the lower bounds can be negative, zero, or positive.
•
The upper bound must be greater than or equal to the lower bound.
•
If only one bound is specified, it is the upper, and the lower is one.
•
In assumed-size arrays, the upper bound of the last dimension is an asterisk.
•
Each bound is an integer expression, and each operand of the expression is a constant, a dummy argument, or a variable in a common block. No array references or user-defined functions are allowed.
Adjustable Arrays
An adjustable array is an array which is a dummy argument, and which has one or more of its dimensions or bounds as integer variables that are either themselves dummy arguments, or are in a common block.
You can declare adjustable arrays in the usual
DIMENSION
,
COMMON
, or type statements. In f77, you can also declare adjustable arrays in a
RECORD statement, if that
RECORD
statement is not inside a structure declaration block.
Example: Adjustable array bounds with arguments, and variables in common;
SUBROUTINE POPUP ( A, B, N )
COMMON / DEFS / M, L, K
REAL A(3:5, 7, M:N), B(N+1:2*N)
The restrictions are:
•
The size of an adjustable array cannot exceed the size of the corresponding actual argument.
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•
In the first caller of the call sequence, the corresponding array must be dimensioned with constants.
Assumed-Size Arrays
An assumed-size array is an array that is a dummy argument, and which has an asterisk as the upper bound of the last dimension.
You can declare assumed-size arrays in the usual
DIMENSION
,
COMMON
, or type statements.
In f77,
the following extensions are allowed:
•
You can declare assumed-size arrays in a
RECORD
statement, if that
RECORD statement is not inside a structure declaration block.
•
You can use an assumed-size array as a unit identifier for an internal file in an I/O statement.
•
You can use an assumed-size array as a runtime format specifier in an I/O statement.
Example: Assumed-size with the upper bound of the last dimension an asterisk:
SUBROUTINE PULLDOWN ( A, B, C )
INTEGER A(5, *), B(*), C(0:1, (mI2:*) ea
An assumed-size array cannot be used in an I/O list.
Array Names with No Subscripts
An array name with no subscripts indicates the entire array. It can appear in any of the following statements:
•
COMMON
•
DATA
•
I/O statements
•
NAMELIST
•
RECORD
statements
•
SAVE
•
Type statements
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In an
EQUIVALENCE
statement, the array name without subscripts indicates the first element of the array.
Array Subscripts
An array element name is an array name qualified by a subscript.
Form of a Subscript
A subscript is a parenthesized list of subscript expressions. There must be one subscript expression for each dimension of the array.
The form of a subscript is:
(
s
[,
s
] … ) where s is a subscript expression. The parentheses are part of the subscript.
Example: Declare a two-by-three array with the declarator:
REAL M(2,3)
With the above declaration, you can assign a value to a particular element, as follows:
M(1,2) = 0.0
The above code assigns
0.0
to the element in row 1, column 2, of array
M
.
Subscript Expressions
Subscript expressions have the following properties and restrictions:
•
A subscript expression is an integer, real, or byte expression. According to the FORTRAN 77 Standard, it must be an integer expression.
•
A subscript expression can contain array element references and function references.
•
Evaluation of a function reference must not alter the value of any other subscript expression within the same subscript.
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•
Each subscript expression is an index into the appropriate dimension of the array.
•
Each subscript expression must be within the bounds for the appropriate dimension of the array.
•
A subscript of the form
(
L1,
…
, Ln
)
, where each Li is the lower bound of the respective dimension, references the first element of the array.
•
A subscript of the form
( U1,
…
, Un), where each Ui is the upper bound of the respective dimension, references the last element of the array.
•
Array element
A(n)
is not necessarily the n th
element of array
A
:
REAL V(-1:8)
V(2) = 0.0
In the above example, the fourth element of
V
is set to zero.
Subscript expressions cannot exceed the range of
INTEGER*4
. It is not controlled, but if the subscript expression is not in the range
(-2147483648, 2147483647), then the results are unpredictable.
Array Ordering
Array elements are usually considered as being arranged with the first subscript as the row number and the second subscript as the column number.
For example:
INTEGER*4 A(3,2)
The elements of
A
are usually mentally arranged like this in 3 rows and 2 columns:
A(1,1)
A(2,1)
A(3,1)
A(1,2)
A(2,2)
A(3,2)
Array elements are stored in column-major order.
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Example: For the array
A
, they are located in memory as follows:
A(1,1) A(2,1) A(3,1) A(1,2)
The inner (leftmost) subscript changes more rapidly.
A(2,2) A(3,2)
2.5 Substrings
A character datum is a sequence of one or more characters. A character
substring is a contiguous portion of a character variable or of a character array element or of a character field of a structured record.
A substring name can be in either of the following two forms:
v
( [
e1
] : [
e2
] )
a
(
s
[,
s
] … ) ( [
e1
] : [
e2
] ) where:
v a
(
s
[,
s
] … )
e1 e2
Character variable name
Character array element name
Leftmost character position of the substring
Rightmost character position of the substring
Both e1 and e2 are integer expressions. They cannot exceed the range of
INTEGER*4
. If the expression is not in the range (-2147483648, 2147483647), then the results are unpredictable.
Example: The string with initial character from the Ith character of S and with the last character from the Lth character of S:
S(I:L)
In the above example, there are L-I+1 characters in the substring.
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The following string has an initial character from the Mth character of the array element
A(J,K)
, with the last character from the Nth character of that element.
A(J,K)(M:N)
In the above example, there are N-M+1 characters in the substring.
Here are the rules and restrictions for substrings:
•
Character positions within a substring are numbered from left to right.
•
The first character position is numbered 1, not 0.
•
The initial and last character positions must be integer expressions.
•
If the first expression is omitted, it is 1.
•
If the second expression is omitted, it is the declared length.
•
The result is undefined unless 0 < I
≤
L
≤
the declared length, where I is the
initial position, and L is the last position.
•
Substrings can be used on the left and right sides of assignments and as procedure actual arguments.
•
Substrings must not be overlapping.
ASTR(2:4) = ASTR(3:5)
is illegal.
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Examples: Substrings—the value of the element in column 2, row 3 is e23
:
&
&
& demo% cat sub.f character v*8 / 'abcdefgh' /, m(2,3)*3 / 'e11', 'e21',
'e12', 'e22',
'e13', 'e23' / print *, v(3:5) print *, v(1:) print *, v(:8) print *, v(:) print *, m(1,1) print *, m(2,1) print *, m(1,2) print *, m(2,2) print *, m(1,3) print *, m(2,3) print *, m(1,3)(2:3) end demo% f77 sub.f sub.f:
MAIN: demo% a.out
cde
abcdefgh
abcdefgh
abcdefgh
e11
e21
e12
e22
e13
e23
13 demo%
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2.6 Structures
A structure is a generalization of an array. ♦
Just as an array is a collection of elements of the same type, a structure is a collection of elements that are not necessarily of the same type.
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As elements of arrays are referenced by using numeric subscripts, so elements of structures are referenced by using element (or field) names.
The structure declaration defines the form of a record by specifying the name, type, size, and order of the fields that constitute the record. Once a structure is defined and named, it can be used in
RECORD
statements, as explained in the following subsections.
Syntax
The structure declaration has the following syntax:
STRUCTURE [/
structure-name
/] [
field-list
]
field-declaration
[
field-declaration
]
. . .
[
field-declaration
]
END STRUCTURE
structure-name field-list field-declaration
Name of the structure
List of fields of the specified structure
Defines a field of the record.
field-declaration is defined in the next section.
Field Declaration
Each field declaration can be one of the following:
•
A substructure—either another structure declaration, or a record that has been previously defined
•
A union declaration, which is described later
•
A FORTRAN 77 type declaration
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Example: A
STRUCTURE
declaration:
STRUCTURE /PRODUCT/
INTEGER*4 ID
CHARACTER*16 NAME
CHARACTER*8 MODEL
REAL*4 COST
REAL*4 PRICE
END STRUCTURE
In the above example, a structure named
PRODUCT
is defined to consist of the five fields
ID
,
NAME
,
MODEL
,
COST
, and
PRICE
. For an example with a field-list, see “Structure within a Structure” on page 54.
Rules and Restrictions for Structures
Note the following:
•
The name is enclosed in slashes, and is optional only in nested structures.
•
If slashes are present, a name must be present.
•
You can specify the field-list within nested structures only.
•
There must be at least one field-declaration.
•
Each structure-name must be unique among structures, although you can use structure names for fields in other structures or as variable names.
•
The only statements allowed between the
STRUCTURE
statement and the
END STRUCTURE
statement are field-declaration statements and
PARAMETER statements. A
PARAMETER
statement inside a structure declaration block is equivalent to one outside.
Rules and Restrictions for Fields
Fields that are type declarations use the identical syntax of normal FORTRAN
77 type statements. All f77
types are allowed, subject to the following rules and restrictions:
•
Any dimensioning needed must be in the type statement. The
DIMENSION statement has no effect on field names.
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•
You can specify the pseudo-name
%FILL
for a field name.
%FILL
is provided for compatibility with other versions of FORTRAN 77. It is not needed in f77
because the alignment problems are taken care of for you. It may be a useful feature if you want to make one or more fields that you cannot reference in some particular subroutine. The only thing that
%FILL does is provide a field of the specified size and type, and preclude referencing it.
•
You must explicitly type all field names. The
IMPLICIT
statement does not apply to statements in a
STRUCTURE
declaration, nor do the implicit
I,J,K,L,M,N
rules apply.
•
You cannot use arrays with adjustable or assumed size in field declarations, nor can you include passed-length
CHARACTER
declarations.
In a structure declaration, the offset of field n is the offset of the preceding field, plus the length of the preceding field, possibly corrected for any adjustments made to maintain alignment. See Appendix C, “Data
Representations,” for a summary of storage allocation.
Record Declaration
The
RECORD
statement declares variables to be records with a specified structure, or declares arrays to be arrays of such records.
The syntax of a
RECORD
statement is:
RECORD /
structure-name
/
record-list
[ ,/
structure-name
/
record-list
]
…
[ ,/
structure-name
/
record-list
]
structure-name record-list
Name of a previously declared structure
List of variables, arrays, or arrays with dimensioning and index ranges, separated by commas.
Example: A
RECORD
that uses the previous
STRUCTURE
example:
RECORD /PRODUCT/ CURRENT, PRIOR, NEXT, LINE(10)
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Each of the three variables,
CURRENT
,
PRIOR
, and
NEXT
, is a record which has the
PRODUCT
structure;
LINE
is an array of 10 such records.
Note the following rules and restrictions for records:
•
Each record is allocated separately in memory.
•
Initially, records have undefined values, unless explicitly initialized.
•
Records, record fields, record arrays, and record-array elements are allowed as arguments and dummy arguments. When you pass records as arguments, their fields must match in type, order, and dimension. The record declarations in the calling and called procedures must match. Within a union declaration, the order of the map fields is not relevant. See “Unions and Maps” on page 56.
•
Record fields are not allowed in
COMMON
statements.
•
Records and record fields are not allowed in
DATA
,
EQUIVALENCE
, or
NAMELIST
statements. Record fields are not allowed in
SAVE
statements.
Record and Field Reference
You can refer to a whole record, or to an individual field in a record, and since structures can be nested, a field can itself be a structure, so you can refer to fields within fields, within fields, and so forth.
The syntax of record and field reference is:
record-name
[.
field-name
] … [.
field-name
]
record-name field-name
Name of a previously defined record variable
Name of a field in the record immediately to the left.
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Example: References that are based on structure and records of the above two examples:
…
RECORD /PRODUCT/ CURRENT, PRIOR, NEXT, LINE(10)
…
CURRENT = NEXT
LINE(1) = CURRENT
WRITE ( 9 ) CURRENT
NEXT.ID = 82
In the above example:
•
The first assignment statement copies one whole record (all five fields) to another record.
•
The second assignment statement copies a whole record into the first element of an array of records.
•
The
WRITE
statement writes a whole record.
•
The last statement sets the
ID
of one record to 82.
Example: Structure and record declarations, record and field assignments: demo% cat str1.f
* str1.f Simple structure
STRUCTURE / S /
INTEGER*4 I
REAL*4 R
END STRUCTURE
RECORD / S / R1, R2
R1.I = 82
R1.R = 2.7182818
R2 = R1
WRITE ( *, * ) R2.I, R2.R
STOP
END demo% f77 -silent str1.f demo% a.out
82 2.718280
demo%
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2
Substructure Declaration
A structure can have a field that is also a structure. Such a field is called a
substructure. You can declare a substructure in one of two ways:
•
A
RECORD
declaration within a structure declaration
•
A structure declaration within a structure declaration (nesting)
Record within a Structure
A nested structure declaration is one that is contained within either a structure declaration or a union declaration. You can use a previously defined record within a structure declaration.
Example: Define structure
SALE
using previously defined record
PRODUCT
:
STRUCTURE /SALE/
CHARACTER*32 BUYER
INTEGER*2 QUANTITY
RECORD /PRODUCT/ ITEM
END STRUCTURE
In the above example, the structure
SALE
contains three fields.
BUYER
,
QUANTITY
, and
ITEM
, where
ITEM
is a record with the structure,
/PRODUCT/
.
Structure within a Structure
You can nest a declaration within a declaration.
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Example: If
/PRODUCT/
is not declared previously, then you can declare it within the declaration of
SALE
:
STRUCTURE /SALE/
CHARACTER*32 BUYER
INTEGER*2 QUANTITY
STRUCTURE /PRODUCT/ ITEM
INTEGER*4 ID
CHARACTER*16 NAME
CHARACTER*8 MODEL
REAL*4 COST
REAL*4 PRICE
END STRUCTURE
END STRUCTURE
Here, the structure
SALE
still contains the same three fields as in the prior example:
BUYER
,
QUANTITY
, and
ITEM
. The field
ITEM
is an example of a field-
list (in this case, a single-element list), as defined under “Structure
Declaration.”
The size and complexity of the various structures determine which style of substructure declaration is best to use in a given situation.
Field Reference in Substructures
You can refer to fields within substructures.
Example: Refer to fields of substructures (
PRODUCT
and
SALE
, from the previous examples, are defined in the current program unit):
…
RECORD /SALE/ JAPAN
…
N = JAPAN.QUANTITY
I = JAPAN.ITEM.ID
…
Data Types and Data Items
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2
56
Rules and Restrictions for Substructures
Note the following:
•
You must define at least one field name for any substructure.
•
No two fields at the same nesting level can have the same name. Fields at different levels of a structure can have the same name; however, doing so might be questionable programming practice.
•
You can use the pseudo-name,
%FILL
, to align fields in a record, and create an unnamed empty field.
•
You must not include a structure as a substructure of itself, at any level of nesting.
Unions and Maps
A union declaration defines groups of fields that share memory at runtime.
Syntaxes
The syntax of a union declaration is:
UNION
map-declaration map-declaration
[
map-declaration
]
…
[
map-declaration
]
END UNION
The syntax of a map declaration is as follows.
MAP
field-declaration
[
field-declaration
]
…
[
field-declaration
]
END MAP
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Fields in a Map
Each field-declaration in a map declaration can be one of the following:
•
Structure declaration
•
Record
•
Union declaration
•
Declaration of a typed data field
A map declaration defines alternate groups of fields in a union. During execution, one map at a time is associated with a shared storage location.
When you reference a field in a map, the fields in any previous map become undefined and are succeeded by the fields in the map of the newly referenced field. The amount of memory used by a union is that of its biggest map.
Example: Declare the structure
/STUDENT/
to contain either
NAME
,
CLASS
, and
MAJOR
—or
NAME
,
CLASS
,
CREDITS
, and
GRAD_DATE
:
STRUCTURE /STUDENT/
CHARACTER*32 NAME
INTEGER*2 CLASS
UNION
MAP
CHARACTER*16 MAJOR
END MAP
MAP
INTEGER*2 CREDITS
CHARACTER*8 GRAD_DATE
END MAP
END UNION
END STRUCTURE
If you define the variable
PERSON
to have the structure
/STUDENT/
from the above example, then
PERSON.MAJOR
references a field from the first map, and
PERSON.CREDITS
references a field from the second map. If the variables of the second map field are initialized, and then the program references the variable
PERSON.MAJOR
, the first map becomes active, and the variables of the second map become undefined.
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2
2.7 Pointers
The
POINTER
statement establishes pairs of variables and pointers. ♦
Each pointer contains the address of its paired variable.
Syntax Rules
The
POINTER
statement has the following syntax:
POINTER (
p1
,
v1
) [, (
p2
,
v2
) … ] where:
•
v1, v2 are pointer-based variables.
•
p1, p2 are the corresponding pointers.
A pointer-based variable is a variable paired with a pointer in a
POINTER statement. A pointer-based variable is usually just called a based variable. The
pointer is the integer variable that contains the address.
Example: A simple
POINTER
statement:
POINTER ( P, V )
Here,
V
is a pointer-based variable, and
P
is its associated pointer.
Usage of Pointers
Normal use of pointer-based variables involves the following steps. The first two steps can be in either order.
1. Define the pairing of the pointer-based variable and the pointer in a
POINTER
statement.
2. Define the type of the pointer-based variable.
The pointer itself is integer type, but in general, it is safer if you not list it in an
INTEGER
statement.
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2
3. Set the pointer to the address of an area of memory that has the appropriate size and type.
You do not normally do anything else explicitly with the pointer.
4. Reference the pointer-based variable.
Just use the pointer-based variable in normal FORTRAN 77 statements—the address of that variable is always from its associated pointer.
Address and Memory
No storage for the variable is allocated when a pointer-based variable is defined, so you must provide an address of a variable of the appropriate type and size, and assign the address to a pointer, usually with the normal assignment statement or data statement.
See Table 6-9 on page 327.
Address by
LOC()
Function
You can obtain the address from the intrinsic function
LOC()
.
Example: Use the
LOC()
function to get an address:
* ptr1.f: Assign an address via LOC()
POINTER ( P, V )
CHARACTER A*12, V*12
DATA A / 'ABCDEFGHIJKL' /
P = LOC( A )
PRINT *, V(5:5)
END
In the above example, the
CHARACTER
statement allocates 12 bytes of storage for
A
, but no storage for
V
. It merely specifies the type of
V
because
V
is a pointer-based variable, then assign the address of
A
to
P
, so now any use of
V will refer to
A
by the pointer
P
. The program prints an
E
.
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60
Memory and Address by
MALLOC()
Function
The function
MALLOC()
allocates an area of memory and returns the address of the start of that area. The argument to the function is an integer specifying the amount of memory to be allocated, in bytes. If successful, it returns a pointer to the first item of the region; otherwise, it returns an integer 0. The region of memory is not initialized in any way.
Example: Memory allocation for pointers, by
MALLOC
:
COMPLEX Z
REAL X, Y
POINTER ( P1, X ), ( P2, Y ), ( P3, Z )
…
P1 = MALLOC ( 10000 )
…
In the above example, we get 10,000 bytes of memory from
MALLOC()
and assign the address of that block of memory to the pointer
P1
.
Deallocation of Memory by
FREE()
Function
The subroutine
FREE()
deallocates a region of memory previously allocated by
MALLOC()
. The argument given to
FREE()
must be a pointer previously returned by
MALLOC()
, but not already given to
FREE()
. The memory is returned to the memory manager, making it unavailable to the programmer.
Example: Deallocate via
FREE
:
POINTER ( P1, X ), ( P2, Y ), ( P3, Z )
…
P1 = MALLOC ( 10000 )
…
CALL FREE ( P1 )
…
In the above example, after getting memory via
MALLOC()
, and after some other instructions, probably using that chunk of memory, we direct
FREE()
to return those same 10,000 bytes to the memory manager.
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Restrictions
The pointers are of type integer, and are automatically typed that way by the compiler. You must not type them yourself.
A pointer-based variable cannot itself be a pointer.
The pointer-based variables can be of any type, including structures.
No storage is allocated when such a pointer-based variable is declared, even if there is a size specification in the type statement.
You cannot use a pointer-based variable as a dummy argument or in
COMMON
,
EQUIVALENCE
,
DATA
, or
NAMELIST
statements.
The dimension expressions for pointer-based variables must be constant expressions in main programs. In subroutines and functions, the same rules apply for pointer-based array variables as for dummy arguments—the expression can contain dummy arguments and variables in common. Any variables in the expressions must be defined with an integer value at the time the subroutine or function is called.
Address expressions cannot exceed the range of
INTEGER*4.
If the expression is not in the range (-2147483648, 2147483647), then the results are unpredictable.
Optimization and Pointers
Pointers have the annoying side effect of reducing the assumptions that the global optimizer can make. For one thing, compare the following:
•
Without pointers, if you call a subroutine or function, the optimizer knows that the call will change only variables in common or those passed as arguments to that call.
•
With pointers, this is no longer valid, since a routine can take the address of an argument and save it in a pointer in common for use in a subsequent call to itself or to another routine.
Therefore, the optimizer must assume that a variable passed as an argument in a subroutine or function call can be changed by any other call. Such an unrestricted use of pointers would degrade optimization for the vast majority of programs that do not use pointers.
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2
62
General Guidelines
There are two alternatives for optimization with pointers.
•
Do not use pointers with optimization level
-O4
.
•
Use a pointer only to identify the location of the data for calculations and pass the pointer to a subprogram. Almost anything else you do to the pointer can yield incorrect results.
The second choice also has a suboption: localize pointers to one routine and do not optimize it, but do optimize the routines that do the calculations. If you put the calling the routines on different files, you can optimize one and not optimize the other.
Example: A relatively “safe” kind of coding with
-O3
or
-O4
:
REAL A, B, V(100,100) !
Within this programming unit,
POINTER ( P, V )
P = MALLOC(10000)
!
do nothing else with P
!
other than getting the address and passing it.
…
CALL CALC ( P, A )
...
END
SUBROUTINE CALC ( ARRAY, X )
...
RETURN
END
If you want to optimize only
CALC
at level
-O4
, then use no pointers in
CALC
.
Some Problematic Code Practices
Any of the following coding practices, and many others, could cause problems with an optimization level of
-O3
or
-O4
:
•
A program unit does arithmetic with the pointer.
•
A subprogram saves the address of any of its arguments between calls.
•
A function returns the address of any of its arguments, although it can return the value of a pointer argument.
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2
•
A variable is referenced through a pointer, but the address of the variable is not explicitly taken with the
LOC()
or
MALLOC()
functions.
Example: One kind of code that could cause trouble with
-O3
or
-O4
:
COMMON A, B, C
POINTER ( P, V )
P = LOC(A) + 4 !
…
←
Possible problems if optimized
The compiler assumes that a reference through
P
may change
A
, but not
B
; this assumption could produce incorrect code.
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FORTRAN 77 Reference Manual
Expressions
An expression is a combination of one or more operands, zero or more operators, and zero or more pairs of parentheses.
This chapter is organized into the following sections:
Expressions, Operators, and Operands
Arithmetic Expressions
Character Expressions
Logical Expressions
Relational Operator
Constant Expressions
Record Assignment
Evaluation of Expressions page 65 page 66 page 74 page 78 page 80 page 81 page 82 page 83
3.1 Expressions, Operators, and Operands
There are three kinds of expressions:
•
An arithmetic expression evaluates to a single arithmetic value.
•
A character expression evaluates to a single value of type character.
•
A logical or relational expression evaluates to a single logical value.
The operators indicate what action or operation to perform.
3
65
66
3
The operands indicate what items to apply the action to. An operand can be any of the following kinds of data items:
•
Constant
•
Variable
•
Array element
•
Function
•
Substring
•
Structured record field (if it evaluates to a scalar data item)
3.2 Arithmetic Expressions
An arithmetic expression evaluates to a single arithmetic value, and its operands have the following types. ♦ indicates a nonstandard feature.
•
BYTE
♦
•
COMPLEX
•
COMPLEX*32
(SPARC only) ♦
•
DOUBLE COMPLEX
♦
•
DOUBLE PRECISION
•
INTEGER
•
LOGICAL
•
REAL
•
REAL*16
(SPARC only) ♦
The operators for an arithmetic expression are any of the following:
If
BYTE
or
LOGICAL
operands are combined with arithmetic operators, they are interpreted as integer data.
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3
Each of these operators is a binary operator in an expression of the form:
a
⊕
b
where a and b are operands, and
⊕
is any one of the
**
,
*
,
/
,
-
, or
+
operators.
Examples: Binary operators:
A-Z
X*B
The operators
+
and
-
are unary operators in an expression of the form:
⊕
b
where b is an operand, and
⊕
is either of the
-
or
+
operators.
Examples: Unary operators:
-Z
+B
Basic Arithmetic Expressions
Each arithmetic operator is shown in its basic expression in the following table:
Table 3-2
Arithmetic Expressions
Expression
a ** z a / z a * z a - z
-z a + z
+z
Meaning
Raise a
to the power z
Divide a
by z
Multiply a
by z
Subtract z
from a
Negate z
Add z
to a
Same as z
Expressions
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3
68
In the absence of parentheses, if there is more than one operator in an expression, then the operators are applied in the order of precedence. With one exception, if the operators are of equal precedence, they are applied left to right.
Table 3-3
Arithmetic Operator Precedence
Operator
**
* /
+ -
Precedence
First
Second
Last
For the left-to-right rule, the one exception is shown by the following example:
F ** S ** Z
The above is evaluated as:
F ** (S ** Z) f77
allows two successive operators. ♦
Example: Two successive operators:
X ** -A * Z
The above expression is evaluated as follows:
X ** (-(A * Z))
In the above example, the compiler starts to evaluate the
**
, but it needs to know what power to raise
X
to; so it looks at the rest of the expression and must choose between
-
and
*
. It first does the
*
, then the
-
, then the
**
.
Some early releases of this FORTRAN 77 incorrectly interpreted
X**-A*Z
as
(X**(-A))*Z
. Current releases correctly interpret
X**-A*Z
” as
“X**(-(A*Z))
, which is compatible with VMS FORTRAN.
FORTRAN 77 Reference Manual
Example: Two successive operators: demo% cat twoops.f
REAL X / 2.0 /, A / 1.0 /, Z / -3.0 /
PRINT *, "X**-A*Z = ", X ** -A*Z
PRINT *, "X**(-(A*Z)) = ", X ** (-(A*Z))
PRINT *, "(X**(-A))*Z = ", (X ** (-A))*Z
PRINT *, "X**-2 = ", X ** -2 !{same in both}
END demo% f77old twoops.f twoops.f:
(Use old)
MAIN: demo% a.out
X**-A*Z = -1.50000
X**(-(A*Z)) = 8.00000
(X**(-A))*Z = -1.50000
X**-2 = 0.250000
demo% f77new -silent twoops.f demo% a.out
X**-A*Z = 8.00000
X**(-(A*Z)) = 8.00000
(X**(-A))*Z = -1.50000
X**-2 = 0.250000
demo%
{Use new}
3
Expressions
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3
Mixed Mode
If both operands have the same type, then the resulting value has that type. If operands have different types, then the weaker of two types is promoted to the stronger type, where the weaker type is the one with less precision or fewer storage units. The ranking is summarized in the following table:
Data Type
BYTE or LOGICAL*1
LOGICAL*2
LOGICAL*4
INTEGER*2
INTEGER*4
INTEGER*8
LOGICAL*8
REAL*4 (REAL)
REAL*8 (DOUBLE PRECISION)
REAL*16 (QUAD PRECISION)
(SPARC only)
COMPLEX*8 (COMPLEX)
COMPLEX*16 (DOUBLE COMPLEX)
COMPLEX*32 (QUAD COMPLEX)
(SPARC only)
Rank
1 (Weakest)
6
7
6
6
8
4
5
2
3
9
10
11 (Strongest)
Note –
REAL*4
,
INTEGER*8
, and
LOGICAL*8
are of the same rank, but they can be the results of different pairs of operands. For example,
INTEGER*8 results if you combine
INTEGER*8
and any of the types between 1-5. Likewise,
REAL*4
results if one of the operands is
REAL*4
, and the other is any of the types between 1-5.
LOGICAL*8
dictates only the 8-byte size of the result.
Example of mixed mode: If
R
is real, and
I
is integer, then the expression:
R * I has the type real, because first
I
is promoted to real, and then the multiplication is performed.
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Rules
Note these rules for the data type of an expression:
•
If there is more than one operator in an expression, then the type of the last operation performed becomes the type of the final value of the expression.
•
Integer operators apply to only integer operands.
Example: An expression that evaluates to zero:
2/3 + 3/4
•
When an
INTEGER*8
operand is mixed with
REAL*4
operands, the result is
REAL*8
.
There is one extension to this: a logical or byte operand in an arithmetic context is used as an integer.
•
Real operators apply to only real operands, or to combinations of byte, logical, integer, and real operands. An integer operand mixed with a real operand is promoted to real; the fractional part of the new real number is zero. For example, if
R
is real, and
I
is integer, then
R+I
is real. However,
(2/3)*4.0
is
0
.
•
Double precision operators apply to only double precision operands, and any operand of lower precision is promoted to double precision. The new least significant bits of the new double precision number are set to zero.
Promoting a real operand does not increase the accuracy of the operand.
•
Complex operators apply to only complex operands. Any integer operands are promoted to real, and they are then used as the real part of a complex operand, with the imaginary part set to zero.
•
Numeric operations are allowed on logical variables. ♦ You can use a logical value any place where the FORTRAN 77 Standard requires a numeric value.
The numeric can be integer
, real
, complex
, double precision
, double complex
, or real*16
(SPARC only). The compiler implicitly converts the logical to the appropriate numeric. Logical operations are allowed on integers, bytes, and characters. If you use these features, your program may not be portable.
Expressions
71
3
72
Example: Some combinations of both integer
and logical
types:
&
COMPLEX C1 / ( 1.0, 2.0 ) /
INTEGER*2 I1, I2, I3
LOGICAL L1, L2, L3, L4, L5
REAL R1 / 1.0 /
DATA I1 / 8 /, I2 / 'W' /, I3 / 0 /
DATA L1/.TRUE./, L2/.TRUE./, L3/.TRUE./, L4/.TRUE./,
L5/.TRUE./
L1 = L1 + 1
I2 = .NOT. I2
L2 = I1 .AND. I3
L3 = I1 .OR. I2
L4 = L4 + C1
L5 = L5 + R1
Resultant Type
For integer operands with a logical operator, the operation is done bit by bit.
The result is an integer.
If the operands are mixed integer and logical, then the logicals are converted to integers, and the result is an integer.
Arithmetic Assignment
The arithmetic assignment statement assigns a value to a variable, array element, or record field. The syntax is:
v
=
e e v
Arithmetic expression, a character constant, or a logical expression
Numeric variable, array element, or record field
Assigning logicals to numerics is allowed, but nonstandard, and may not be portable. The resultant data type is, of course, the data type of v. ♦
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Execution of an arithmetic assignment statement causes the evaluation of the expression e, and conversion to the type of v (if types differ), and assignment of
v with the resulting value typed according to the table below.
Character constants can be assigned to variables of type integer or real. Such a constant can be a Hollerith constant or a string in apostrophes or quotes. The characters are transferred to the variables without any conversion of data. This practice is nonstandard and may not be portable. ♦
Type of v
INTEGER*2
,
INTEGER*4
, or
INTEGER*8
REAL
REAL*8
REAL*16
(SPARC only)
DOUBLE PRECISION
COMPLEX*8
COMPLEX*16
COMPLEX*32
(SPARC only)
Type of e
INT(
e
)
REAL(
e
)
DBLE(
e
)
QREAL(
e
)
(SPARC only)
DBLE(
e
)
CMPLX(
e
)
DCMPLX(
e
)
QCMPLX(
e
)
(SPARC only)
Note –
Some types of e depend on whether or not you compile with the
-r8 option. See the FORTRAN 77 4.0 User’s Guide for a description of
-r8
.
Expressions
73
74
3
Example: Arithmetic assignment:
INTEGER I2*2, J2*2, I4*4
LOGICAL L1, L2
REAL R4*4, R16*16 !
(The *16 is for SPARC only)
DOUBLE PRECISION DP
COMPLEX C8, C16*16
J2 = 29002
I2 = J2
I4 = (I2 * 2) + 1
DP = 6.4D0
QP = 9.8Q1
R4 = DP
R16 = QP
C8 = R1
C8 = ( 3.0, 5.0 )
I2 = C8
C16 = C8
C8 = L1
R4 = L2
3.3 Character Expressions
A character expression is an expression whose operands have the character type.
It evaluates to a single value of type character, with a size of one or more characters. The only character operator is the concatenation operator,
//
.
Expression
a
//
z
Meaning
Concatenate a with z
.
The result of concatenating two strings is a third string that contains the characters of the left operand followed immediately by the characters of the right operand. The value of a concatenation operation a//z
is a character string whose value is the value of a
concatenated on the right with the value of z
, and whose length is the sum of the lengths of a
and z
.
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The operands can be any of the following kinds of data items:
•
Character constant
•
Character variable
•
Character array element
•
Character function
•
Substring
•
Structured record field (if it evaluates to a scalar character data item)
Examples: Character expressions, assuming
C
,
S
, and
R.C
are characters:
'wxy'
'AB' // 'wxy'
C
C // S
C(4:7)
R.C
Note the following exceptions:
•
Control characters ♦
—One way to enter control characters is to hold down the Control key and press another key. Most control characters can be entered this way, but not Control-A, Control-B, Control-C, or Control-J.
Example: A valid way to enter a Control-C:
CHARACTER etx etx = CHAR(3)
•
Multiple byte characters ♦ —Multiple byte characters, such as Kanji, are allowed in comments and strings.
Expressions
75
3
Character String Assignment
The form of the character string assignment is:
v
=
e
e
v
Expression giving the value to be assigned
Variable, array element, substring, or character record field
The meaning of character assignment is to copy characters from the right to the left side.
Execution of a character assignment statement causes evaluation of the character expression and assignment of the resulting value to v.
•
If e is longer than v, characters on the right are truncated.
•
If e is shorter than v, blank characters are padded on the right.
Example: The following program below displays joined
∆∆
:
CHARACTER A*4, B*2, C*8
A = 'join'
B = 'ed'
C = A // B
PRINT *, C
END
Also, this program displays the equal
string:
IF ( ('ab' // 'cd') .EQ. 'abcd' ) PRINT *, 'equal'
END
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FORTRAN 77 Reference Manual
Example: Character assignment:
CHARACTER BELL*1, C2*2, C3*3, C5*5, C6*6
REAL Z
C2 = 'z'
C3 = 'uvwxyz'
C5 = 'vwxyz'
C5(1:2) = 'AB'
C6 = C5 // C2
I = 'abcd'
Z = 'wxyz'
BELL = CHAR(7) !
Control Character
(^G)
The results are:
C2
C3
C5
C6
I
Z
BELL gets gets gets gets gets gets gets
'z
∆
'
'uvw'
'ABxyz'
'ABxyzz'
'abcd'
'wxyz'
07 hex
Example 4: A Hollerith assignment: ♦
CHARACTER S*4
INTEGER I2*2, I4*4
REAL R
S = 4Hwxyz
I2 = 2Hyz
I4 = 4Hwxyz
R = 4Hwxyz
A trailing blank
That is, the
'z'
from
C2
Control-G, a bell
3
Expressions
77
78
3
Rules of Assignment
Here are the rules for character assignments:
•
If the left side is longer than the right, it is padded with trailing blanks.
•
If the left side is shorter than the right, trailing characters are discarded.
•
The left and right sides of a character assignment can share storage. ♦
Example: The following program displays abcefggh
: ♦
CHARACTER S*8
S = 'abcdefgh'
S(4:6) = S(5:7)
WRITE(*,*) S
END
3.4 Logical Expressions
A logical expression is a sequence of one or more logical operands and logical operators. It evaluates to a single logical value. The operators can be any of the following.
Table 3-4
Logical Operators
Operator
.AND.
.OR.
.NEQV.
.XOR.
.EQV.
.NOT.
Standard Name
Logical conjunction
Logical disjunction (inclusive
OR
)
Logical nonequivalence
Logical exclusive
OR
Logical equivalence
Logical negation
The period delimiters are necessary.
Two logical operators cannot appear consecutively, unless the second one is the
.NOT.
operator.
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3
Logical operators are evaluated according to the following precedence:
Table 3-5
Logical Operator Precedence
Operator
.NOT.
.AND.
.OR.
.NEQV.,.XOR., .EQV.
Precedence
Highest
Lowest
If the logical operators are of equal precedence, they are evaluated left to right.
If the logical operators appear along with the various other operators in a logical expression, the precedence is as follows.
Table 3-6
Operator Precedence
Operator
Arithmetic
Character
Relational
Logical
Precedence
Highest
Lowest
The following table shows the meanings of simple expressions:
Table 3-7
Logical Expressions and Their Meanings
Expression
X .AND. Y
X .OR. Y
X .NEQV. Y
X .XOR. Y
X .EQV. Y
.NOT. X
Meaning
Both
X
and
Y
are true.
Either
X
or
Y
, or both, are true.
X
and
Y
are not both true and not both false.
Either
X
or
Y
is true, but not both.
X
and
Y
are both true or both false.
Logical negation.
This is the syntax for the assignment of the value of a logical expression to a logical variable:
v
=
e
Expressions
79
80
3
where:
e A logical expression, an integer between –128 and 127, or a single character constant
v A logical variable, array element, or record field
Execution of a logical assignment statement causes evaluation of the logical expression e and assignment of the resulting value to v. If e is a logical expression, rather than an integer between -128 and 127, or a single character constant, then e must have a value of either true or false.
Logical expressions of any size can be assigned to logical variables of any size.
Assigning numerics to logicals is allowed. This practice is nonstandard, however, and is not portable. ♦
Example: A logical assignment:
LOGICAL B1*1, B2*1
LOGICAL L3, L4
B2 = B1
B1 = L3
L4 = .TRUE.
3.5 Relational Operator
A relational operator compares two arithmetic expressions, or two character expressions, and evaluates to a single logical value. The operators can be any of the following:
Table 3-8
Relational Operators
Operator
.LT.
.LE.
.EQ.
.NE.
.GT.
.GE.
Meaning
Less than
Less than or equal
Equal
Not equal
Greater than
Greater than or equal
The period delimiters are necessary.
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3
All relational operators have equal precedence. Character and arithmetic operators have higher precedence than relational operators.
For a relational expression, first each of the two operands is evaluated, and then the two values are compared. If the specified relationship holds, then the value is true; otherwise, it is false.
Example: Relational operators:
NODE .GE. 0
X .LT. Y
U*V .GT. U-V
M+N .GT. U-V
Mixed mode: integer
M+N
is promoted to real
STR1 .LT. STR2
where
STR1
and
STR2
are type character
S .EQ. 'a'
where
S
is type character
For character relational expressions:
•
“Less than” means “precedes in the ASCII collating sequence.”
•
If one operand is shorter than the other, the shorter one is padded on the right with blanks to the length of the longer.
3.6 Constant Expressions
A constant expression is made up of explicit constants and parameters and the
FORTRAN 77 operators. Each operand is either itself another constant expression, a constant, a symbolic name of a constant, or one of the intrinsic functions, such as the following:
LOC, CHAR
IAND, IOR, IEOR, ISHFT
AND, OR, NOT, XOR, LSHIFT, RSHIFT, LGE, LGT, LLE, LLT
MIN, MAX, ABS, MOD, ICHAR, ANINT, NINT, DIM
DPROD, CMPLX, CONJG, AIMAG
INT, IFIX
The functions,
IAND
,
IOR
,
IEOR
, and
ISHFT
, are also available, or you can use the corresponding
AND
,
OR
,
XOR
,
LSHIFT
, or
RSHIFT
.
Expressions
81
82
3
Examples: Constant expressions:
PARAMETER (L=29002), (P=3.14159), (C='along the ')
PARAMETER ( I=L*2, V=4.0*P/3.0, S=C//'riverrun' )
PARAMETER ( M=MIN(I,L), IA=ICHAR('A') )
PARAMETER ( Q=6.4Q6, D=2.3D9 )
K = 66 * 80
VOLUME = V*10**3
DO I = 1, 20*3
There are a few restrictions on constant expressions:
•
Constant expressions are permitted wherever a constant is allowed, except they are not allowed in
DATA
or standard
FORMAT
statements.
•
Constant expressions are permitted in variable format expressions. ♦
•
Exponentiation to a floating-point power is not allowed; a warning is issued.
Example: Exponentiation to a floating-point power is not allowed: demo% cat ConstExpr.f parameter (T=2.0*(3.0**2.5)) write(*,*) t end demo% f77 ConstExpr.f
ConstExpr.f:
MAIN:
"ConstExpr.f", line 1: Warning: parameter t set to a nonconstant demo% a.out
31.1769
demo%
3.7 Record Assignment
The general form of record assignment is: ♦
v
=
e
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3
where
e v
A record or record field
A record or record field
Both e and v must have the same structure. That is, each must have the same number of fields, and corresponding fields must be of the same type and size.
Example: A record assignment and a record-field assignment:
STRUCTURE /PRODUCT/
INTEGER*4 ID
CHARACTER*16 NAME
CHARACTER*8 MODEL
REAL*4 COST
REAL*4 PRICE
END STRUCTURE
RECORD /PRODUCT/ CURRENT, PRIOR, NEXT, LINE(10)
…
CURRENT = NEXT
LINE(1) = CURRENT
WRITE ( 9 ) CURRENT
NEXT.ID = 82
In the above example, the first assignment statement copies one whole record
(all five fields) to another record; the second assignment statement copies a whole record into the first element of an array of records; the
WRITE
statement writes a whole record; and the last statement sets the
ID
of one record to 82.
3.8 Evaluation of Expressions
The following restrictions apply to all arithmetic, character, relational, and logical expressions:
•
If you reference any one of these items in an expression, variable, array element, character substring, record field, pointer, or function, then that item must be defined at the time the reference is executed.
•
An integer operand must be defined with an integer value, and not with a statement label value by an
ASSIGN
statement.
Expressions
83
3
•
All the characters of a substring that are referenced must be defined at the time the reference is executed.
•
The execution of a function reference must not alter the value of any other entity within the same statement.
•
The execution of a function reference must not alter the value of any entity in common that affects the value of any other function reference in the same statement.
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FORTRAN 77 Reference Manual
Statements
This chapter describes the FORTRAN 77 statements. The nonstandard statements are indicated with a small black diamond (♦).
4
4.1
ACCEPT
Syntax
The
ACCEPT
♦ statement reads from standard input.
ACCEPT
f
[,
iolist
]
ACCEPT
grname f iolist grname
Format identifier
List of variables, substrings, arrays, and records
Name of the namelist group
85
86
4
Description
ACCEPT
f
[,
iolist
]
is equivalent to
READ
f
[,
iolist
]
and is for compatibility with older versions of FORTRAN 77. An example of list-directed input:
REAL VECTOR(10)
ACCEPT *, NODE, VECTOR
4.2
ASSIGN
The
ASSIGN
statement assigns a statement label to a variable.
Syntax
ASSIGN
s
TO
i i s
Statement label
Integer variable
Description
The label s is the label of an executable statement or a
FORMAT
statement.
The statement label must be the label of a statement that is defined in the same program unit as the
ASSIGN
statement.
The integer variable i, once assigned a statement label, can be reassigned the same statement label, a different label, or an integer.
Once a variable is defined as a statement label, you can reference in:
•
An assigned
GO TO
statement
•
An input/output statement, as a format identifier
Restrictions
Define a variable with a statement label before you reference it as a label.
i must be
INTEGER*4
or
INTEGER*8
, not
INTEGER*2
.
FORTRAN 77 Reference Manual
While i is defined with a statement label value, do no arithmetic with i.
4
Examples
Example 1: Assign the statement number of an executable statement:
ASSIGN 9 TO K
GO TO K
…
9 WRITE (*,*) 'Assigned ', K, ' to K'
In the above example, the output shows the address, not 9.
Example 2: Assign the statement number of a format statement:
INTEGER PHORMAT
2 FORMAT ( A80 )
ASSIGN 2 TO PHORMAT
…
WRITE ( *, PHORMAT ) 'Assigned a FORMAT statement no.'
4.3 Assignment
The assignment statement assigns a value to a variable, substring, array element, record, or record field.
Statements
87
88
4
Syntax v = e e v
Expression giving the value to be assigned
Variable, substring, array element, record, or record field
Description
The value can be a constant or the result of an expression. The kinds of assignment statements: are arithmetic, logical, character, and record assignments.
Arithmetic Assignment
v is of numeric type and is the name of a variable, array element, or record field.
e is an arithmetic expression, a character constant, or a logical expression.
Assigning logicals to numerics is nonstandard, and may not be portable; the resultant data type is, of course, the data type of v. ♦
Execution of an arithmetic assignment statement causes the evaluation of the expression e, and conversion to the type of v (if types differ), and assignment of
v with the resulting value typed according to the following table.
Table 4-1
Arithmetic Assignment Conversion Rules
Type of v
INTEGER*2
,
INTEGER*4
, or
INTEGER*8
REAL
REAL*8
REAL*16
(SPARC only)
DOUBLE PRECISION
COMPLEX*8
COMPLEX*16
COMPLEX*32
(SPARC only)
Type of e
INT(
e
)
REAL(
e
)
REAL*8
QREAL(
e
)
(SPARC only)
DBLE(
e
)
CMPLX(
e
)
DCMPLX(
e
)
QCMPLX(
e
)
(SPARC only)
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4
Note –
Some types of e depend on whether or not you compile with the
-r8 option. See the FORTRAN 77 4.0 User’s Guide for a description of
-r8
.
Example: An assignment statement:
REAL A, B
DOUBLE PRECISION V
V = A * B
The above code is compiled exactly as if it were the following:
REAL A, B
DOUBLE PRECISION V
V = DBLE( A * B )
Logical Assignment
v is the name of a variable, array element, or record field of type logical.
e is a logical expression, or an integer between -128 and 127, or a single character constant.
Execution of a logical assignment statement causes evaluation of the logical expression e and assignment of the resulting value to v. If e is a logical expression (rather than an integer between -128 and 127, or a single character constant), then e must have a value of either true or false.
Logical expressions of any size can be assigned to logical variables of any size.
The section on the
LOGICAL
statement provides more details on the size of logical variables.
Character Assignment
The constant can be a Hollerith constant or a string of characters delimited by apostrophes (
'
) or quotes (
"
). The character string cannot include the control characters Control-A, Control-B, or Control-C; that is, you cannot hold down the Control key and press the A, B, or C keys. If you need those control characters, use the char()
function.
Statements
89
4
If you use quotes to delimit a character constant, then you cannot compile with the
-xl
option, because, in that case, a quote introduces an octal constant. The characters are transferred to the variables without any conversion of data, and may not be portable.
Character expressions which include the
//
operator can be assigned only to items of type
CHARACTER
. Here, the v is the name of a variable, substring, array element, or record field of type
CHARACTER
; e is a character expression.
Execution of a character assignment statement causes evaluation of the character expression and assignment of the resulting value to v. If the length of
e is more than that of v, characters on the right are truncated. If the length of e is less than that of v, blank characters are padded on the right.
Record Assignment
v and e are each a record or record field. ♦
The e and v must have the same structure. They have the same structure if any of the following occur:
•
Both e and v are fields with the same elementary data type.
•
Both e and v are records with the same number of fields such that corresponding fields are the same elementary data type.
•
Both e and v are records with the same number of fields such that corresponding fields are substructures with the same structure as defined
in 2, above.
The sections on the
RECORD
and
STRUCTURE
statements have more details on the structure of records.
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FORTRAN 77 Reference Manual
Examples
Example 1: Arithmetic assignment:
INTEGER I2*2, J2*2, I4*4
REAL R1, QP*16 !
(The
*16
is for SPARC only)
DOUBLE PRECISION DP
COMPLEX C8, C16*16, QC*32 !
(The
*32
is for SPARC only)
J2 = 29002
I2 = J2
I4 = (I2 * 2) + 1
DP = 6.4D9
QP = 6.4Q9
R1 = DP
C8 = R1
C8 = ( 3.0, 5.0 )
I2 = C8
C16 = C8
C32 = C8
Example 2: Logical assignment:
LOGICAL B1*1, B2*1
LOGICAL L3, L4
L4 = .TRUE.
B1 = L4
B2 = B1
Example 3: Hollerith assignment:
CHARACTER S*4
INTEGER I2*2, I4*4
REAL R
S = 4Hwxyz
I2 = 2Hyz
I4 = 4Hwxyz
R = 4Hwxyz
4
Statements
91
4
92
Example 4: Character assignment:
CHARACTER BELL*1, C2*2, C3*3, C5*5, C6*6
REAL Z
C2 = 'z'
C3 = 'uvwxyz'
C5 = 'vwxyz'
C5(1:2) = 'AB'
C6 = C5 // C2
BELL = CHAR(7) !
Control Character (
^G
)
The results of the above are:
C2
C3
C5
C6
BELL gets
'z
∆
' gets
'uvw' gets
'ABxyz' gets
'ABxyzz' gets 07 hex
That is, a trailing blank
That is, an extra
z
left over from
C5
That is, Control-G, a bell
Example 5: Record assignment and record field assignment:
STRUCTURE /PRODUCT/
INTEGER*4 ID
CHARACTER*16 NAME
CHARACTER*8 MODEL
REAL*4 COST
REAL*4 PRICE
END STRUCTURE
RECORD /PRODUCT/ CURRENT, PRIOR, NEXT, LINE(10)
…
CURRENT = NEXT !
Record to record
LINE(1) = CURRENT !
Record to array element
WRITE ( 9 ) CURRENT !
Write whole record
NEXT.ID = 82 !
Assign a value to a field
FORTRAN 77 Reference Manual
4
4.4
AUTOMATIC
The
AUTOMATIC
♦ statement makes each recursive invocation of the subprogram have its own copy of the specified items. It also makes the specified items become undefined outside the subprogram when the subprogram exits through a
RETURN
statement.
Syntax
AUTOMATIC
vlist vlist
List of variables and arrays
Description
For automatic variables, there is one copy for each invocation of the procedure.
To avoid local variables becoming undefined between invocations, f77 classifies every variable as either static or automatic with all local variables being static by default. For other than the default, you can declare variables as static or automatic in a
STATIC
♦,
AUTOMATIC
♦, or
IMPLICIT
statement.
Compare with
-stackvar
option in the FORTRAN 77 4.0 User’s Guide.
One usage of
AUTOMATIC
is to declare all automatic at the start of a function.
Example: Recursive function with implicit automatic:
INTEGER FUNCTION NFCTRL( I )
IMPLICIT AUTOMATIC (A-Z)
...
RETURN
END
Local variables and arrays are static by default, so in general, there is no need to use
SAVE
. You can still use
SAVE
to ensure portability. Also,
SAVE
is safer if you leave a subprogram by some way other than a
RETURN
.
Restrictions
Automatic variables and arrays cannot appear in
DATA
or
SAVE
statements.
Statements
93
4
Arguments and function values cannot appear in
DATA
,
RECORD
,
STATIC
, or
SAVE
statements because f77
always makes them automatic.
Examples
Example: Some other uses of
AUTOMATIC
:
AUTOMATIC A, B, C
REAL P, D, Q
AUTOMATIC P, D, Q
IMPLICIT AUTOMATIC (X-Z)
Example: Structures are unpredictable if
AUTOMATIC
: demo% cat autostru.f
AUTOMATIC X
STRUCTURE /ABC/
INTEGER I
END STRUCTURE
RECORD /ABC/ X ! X
is automatic. It cannot be a structure.
X.I = 1
PRINT '(I2)', X.I
END demo% f77 -silent autostru.f demo% a.out
*** TERMINATING a.out
*** Received signal 10 (SIGBUS)
Bus Error (core dumped) demo%
Note –
An automatic structure sometimes works; sometimes, it core dumps.
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4
Restrictions
An
AUTOMATIC
statement and a type statement cannot be combined to make an
AUTOMATIC
type statement. For example, the statement:
AUTOMATIC REAL X does not declare the variable
X
to be both
AUTOMATIC
and
REAL
; it declares the variable
REALX
to be
AUTOMATIC
.
4.5
BACKSPACE
The
BACKSPACE
statement positions the specified file to just before the preceding record.
Syntax
BACKSPACE
u
BACKSPACE( [UNIT= ]
u
[, IOSTAT=
ios
] [, ERR=
s
] )
u ios s
Unit identifier of the external unit connected to the file
I/O status specifier, integer variable, or an integer array element
Error specifier: s must be the label of an executable statement in the same program unit in which the
BACKSPACE
statement occurs.
Program control is transferred to the label in case of an error during the execution of the
BACKSPACE
statement.
Description
BACKSPACE
in a terminal file has no effect.
u must be connected for sequential access. Execution of a
BACKSPACE
statement on a direct-access file is not defined in the FORTRAN 77 Standard, and is unpredictable. We do not recommend using a
BACKSPACE
statement on a
direct-access file or an append access file.
Statements
95
4
Execution of the
BACKSPACE
statement modifies the file position, as follows:
Prior to Execution After Execution
Beginning of the file
Beyond the endfile record
Remains unchanged
Before the endfile record
Beginning of the previous record Start of the same record
Examples
Example 1: Simple backspace:
BACKSPACE 2
LUNIT = 2
BACKSPACE LUNIT
Example 2
:
Backspace with error tra p
:
INTEGER CODE
BACKSPACE ( 2, IOSTAT=CODE, ERR=9 )
…
9 WRITE (*,*) 'Error during BACKSPACE'
STOP
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4
4.6
BLOCK DATA
The
BLOCK DATA
statement identifies a subprogram that initializes variables and arrays in labeled common blocks.
Syntax
BLOCK DATA
[ name ]
name
Symbolic name of the block data subprogram in which the
BLOCK DATA statement appears. This parameter is optional. It is a global name.
Description
A block data subprogram can contain as many labeled common blocks and data initializations as desired.
The
BLOCK DATA
statement must be the first statement in a block data subprogram.
The only other statements that can appear in a block data subprogram are:
•
COMMON
•
DATA
•
DIMENSION
•
END
•
EQUIVALENCE
•
IMPLICIT
•
PARAMETER
•
RECORD
•
SAVE
•
STRUCTURE
•
Type statements
Only an entity defined in a labeled common block can be initially defined in a block data subprogram.
If an entity in a labeled common block is initially defined, all entities having storage units in the common block storage sequence must be specified, even if they are not all initially defined.
Statements
97
98
4
Restrictions
Only one unnamed block data subprogram can appear in the executable program.
The same labeled common block cannot be specified in more than one block data subprogram in the same executable program.
The optional parameter name must not be the same as the name of an external procedure, main program, common block, or other block data subprogram in the same executable program. The name must not be the same as any local name in the subprogram.
Example
BLOCK DATA INIT
COMMON /RANGE/ X0, X1
DATA X0, X1 / 2.0, 6.0 /
END
4.7
BYTE
The
BYTE
♦ statement specifies the type to be 1-byte integer. It optionally specifies array dimensions and initializes with values.
Syntax
BYTE
v
[/
c
/]
…
v
Name of a symbolic constant, variable, array, array declarator, function, or dummy function
c
List of constants for the immediately preceding name
Description
This is a synonym for
LOGICAL*1
. A
BYTE
type item can hold the logical values
.TRUE.
,
.FALSE.
, one character, or an integer between –128 and 127.
FORTRAN 77 Reference Manual
4
Example
&
BYTE BIT3 / 8 /, C1 / 'W' /,
COUNTER /0/, M /127/, SWITCH / .FALSE. /
4.8
CALL
The
CALL
statement branches to the specified subroutine, executes the subroutine, and returns to the calling program after finishing the subroutine.
Syntax
CALL
sub
[ ( [
ar
[,
ar
] … ] ) ]
sub
Name of the subroutine to be called
ar
Actual argument to be passed to the subroutine
Description
Arguments are separated by commas.
The FORTRAN 77 Standard requires that actual arguments in a
CALL statement must agree in order, number, and type with the corresponding formal arguments of the referenced subroutine. The compiler checks this only when the
-XlistE
option is on.
Recursion is allowed. A subprogram can call itself directly, or indirectly by calling another subprogram that in turns calls this subroutine. Such recursion is nonstandard. ♦
An actual argument, ar, must be one of the following:
•
An expression
•
An intrinsic function permitted to be passed as an argument; for a list of the intrinsics that cannot be actual arguments, see Table 4-3.
•
An external function name
•
A subroutine name
Statements
99
100
4
•
An alternate return specifier,
*
or
&, followed by a statement number. The
& is nonstandard. ♦
The simplest expressions, and most frequently used, include such constructs as:
•
Constant
•
Variable name
•
Array name
•
Formal argument, if the
CALL
statement is inside a subroutine
•
Record name
If a subroutine has no arguments, then a
CALL
statement that references that subroutine must not have any actual arguments. A pair of empty matching parentheses can follow the subroutine name.
Execution of the
CALL
statement proceeds as follows:
1. All expressions (arguments) are evaluated.
2. All actual arguments are associated with the corresponding formal arguments, and the body of the subroutine is executed.
3. Normally, the control is transferred back to the statement following the
CALL
statement upon executing a
RETURN
statement or an
END
statement in the subroutine. If an alternate return in the form of
RETURN
n is executed, then control is transferred to the statement specified by the n alternate return specifier in the
CALL
statement.
Examples
Example 1: Character string:
CHARACTER *25 TEXT
TEXT = 'Some kind of major screwup'
CALL OOPS ( TEXT )
END
SUBROUTINE OOPS ( S )
CHARACTER S*(*)
WRITE (*,*) S
END
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4
Example 2: Alternate return:
CALL RANK ( N, *8, *9 )
WRITE (*,*) 'OK - Normal Return'
STOP
8 WRITE (*,*) 'Minor - 1st alternate return'
STOP
9 WRITE (*,*) 'Major - 2nd alternate return'
STOP
END
SUBROUTINE RANK ( N, *, * )
IF ( N .EQ. 0 ) RETURN
IF ( N .EQ. 1 ) RETURN 1
RETURN 2
END
Example 3: Another form of alternate return; the
&
is nonstandard: ♦
CALL RANK ( N, &8, &9 )
Example 4: Array, array element, and variable:
REAL M(100,100), Q(2,2), Y
CALL SBRX ( M, Q(1,2), Y )
…
END
SUBROUTINE SBRX ( A, D, E )
REAL A(100,100), D, E
…
RETURN
END
In this example, the real array
M
matches the real array,
A
, and the real array element
Q(1,2)
matches the real variable,
D
.
Statements
101
102
4
Example 5: A structured record and field; the record is nonstandard: ♦
STRUCTURE /PRODUCT/
INTEGER*4 ID
CHARACTER*16 NAME
CHARACTER*8 MODEL
REAL*4 COST
REAL*4 PRICE
END STRUCTURE
RECORD /PRODUCT/ CURRENT, PRIOR
CALL SBRX ( CURRENT, PRIOR.ID )
…
END
SUBROUTINE SBRX ( NEW, K )
STRUCTURE /PRODUCT/
INTEGER*4 ID
CHARACTER*16 NAME
CHARACTER*8 MODEL
REAL*4 COST
REAL*4 PRICE
END STRUCTURE
RECORD /PRODUCT/ NEW
…
RETURN
END
In the above example, the record
NEW
matches the record
CURRENT
, and the integer variable,
K
, matches the record field,
PRIOR.OLD
.
4.9
CHARACTER
The
CHARACTER
statement specifies the type of a symbolic constant, variable, array, function, or dummy function to be character.
Optionally, it initializes any of the items with values and specifies array dimensions.
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4
Syntax
CHARACTER [*
len
[,]]
v
[*
len
/
c
/]] …
v len
Name of a symbolic constant, variable, array, array declarator, function, or dummy function
Length in characters of the symbolic constant, variable, array element, or function
c
List of constants for the immediately preceding name
Description
Each character occupies 8 bits of storage, aligned on a character boundary.
Character arrays and common blocks containing character variables are packed in an array of character variables. The first character of one element follows the last character of the preceding element, without holes.
The length, len must be greater than 0. If len is omitted, it is assumed equal to
1.
For local and common character variables, symbolic constants, dummy arguments, or function names, len can be an integer constant, or a parenthesized integer constant expression.
For dummy arguments or function names, len can have another form: a parenthesized asterisk, that is,
CHARACTER*(*)
, which denotes that the function name length is defined in referencing the program unit, and the dummy argument has the length of the actual argument.
For symbolic constants, len can also be a parenthesized asterisk, which indicates that the name is defined as having the length of the constant. This is shown in Example 5 in the next section.
The list c of constants can be used only for a variable, array, or array declarator.
There can be only one constant for the immediately preceding variable, and one constant for each element of the immediately preceding array.
Statements
103
104
4
Examples
Example 1: Character strings and arrays of character strings:
CHARACTER*17 A, B(3,4), V(9)
CHARACTER*(6+3) C
The above code is exactly equivalent to the following:
CHARACTER A*17, B(3,4)*17, V(9)*17
CHARACTER C*(6+3)
Both of the above two examples are equivalent to the nonstandard variation: ♦
CHARACTER A*17, B*17(3,4), V*17(9)!
nonstandard
There are no null (zero-length) character-string variables. A one-byte character string assigned a null constant has the length zero.
Example 2: No null character-string variables:
CHARACTER S*1
S = ''
During execution of the assignment statement, the variable
S
is precleared to blank, and then zero characters are moved into
S
, so
S
contains one blank; because of the declaration, the intrinsic function
LEN(S)
will return a length of
1
. You cannot declare a size of less than 1, so this is the smallest length string variable you can get.
Example 3: Dummy argument character string with constant length:
SUBROUTINE SCHLEP ( A )
CHARACTER A*32
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4.10
CLOSE
4
Example 4: Dummy argument character string with length the same as corresponding actual argument:
SUBROUTINE SCHLEP ( A )
CHARACTER A*(*)
…
Example 5: Symbolic constant with parenthesized asterisk:
CHARACTER *(*) INODE
PARAMETER ( INODE = 'Warning: INODE clobbered!' )
The intrinsic function
LEN(INODE)
returns the actual declared length of a character string. This is mainly for use with
CHAR*(*)
dummy arguments.
Example 6: The
LEN
intrinsic function:
CHARACTER A*17
A = "xyz"
PRINT *, LEN( A )
END
The above program displays
17
, not
3
.
The
CLOSE
statement disconnects a file from a unit.
Statements
105
4
106
Syntax
CLOSE( [ UNIT=]
u [,
STATUS
= sta
] [, IOSTAT
= ios
] [, ERR
= s
] )
u sta ios
Unit identifier for an external unit. If
UNIT=
is not used, then u must be first.
Determines the disposition of the file—sta is a character expression whose value, when trailing blanks are removed, can be
KEEP
or
DELETE
. The default value for the status specifier is
KEEP
. For temporary (scratch) files, sta is forced to
DELETE
always. For other files besides scratch files, the default
sta is
KEEP
.
I/O status specifier—ios must be an integer variable or an integer array element.
s
Error specifier—s must be the label of an executable statement in the same program containing the
CLOSE
statement. The program control is transferred to this statement in case an error occurs while executing the
CLOSE statement.
Description
For tape, it is more reliable to use the
TOPEN()
routines.
The options can be specified in any order.
The
DISP=
and
DISPOSE=
options are allowable alternates for
STATUS=
, with a warning, if the
-ansi
flag is set.
Execution of
CLOSE
proceeds as follows:
1. The specified unit is disconnected.
2. If sta is
DELETE
, the file connected to the specified unit is deleted.
3. If an
IOSTAT
argument is specified, ios is set to zero if no error was encountered; otherwise, it is set to a positive value.
Comments
All open files are closed with default sta at normal program termination.
Regardless of the specified sta, scratch files, when closed, are always deleted.
Execution of a
CLOSE
statement specifying a unit that does not exist, or a unit that has no file connected to it, has no effect.
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Execution of a
CLOSE
statement specifying a unit zero (standard error) is not allowed, but you can reopen it to some other file.
The unit or file disconnected by the execution of a
CLOSE
statement can be connected again to the same, or a different, file or unit.
Examples
Example 1: Close and keep:
CLOSE ( 2, STATUS='KEEP')
Example 2: Close and delete:
CLOSE ( 2, STATUS='DELETE', IOSTAT=I )
Example 3: Close and delete a scratch file even though the status is
KEEP
:
OPEN ( 2, STATUS='SCRATCH')
…
CLOSE ( 2, STATUS='KEEP', IOSTAT=I )
Statements
107
4
4.11
COMMON
The
COMMON
statement defines a block of main memory storage so that different program units can share the same data without using arguments.
Syntax
COMMON [/[
cb
]/]
nlist
[[,]/[
cb
] /
nlist
] …
cb
Common block name
nlist
List of variable names, array names, and array declarators
Description
If the common block name is omitted, then blank common block is assumed.
Any common block name including blank common can appear more than once in
COMMON
statements in the same program unit. The list nlist following each successive appearance of the same common block name is treated as a continuation of the list for that common block name.
The size of a common block is the sum of the sizes of all the entities in the common block, plus space for alignment.
Within a program, all common blocks in different program units that have the same name must be of the same size. However, blank common blocks within a program are not required to be of the same size.
Restrictions
Formal argument names and function names cannot appear in a
COMMON statement.
An
EQUIVALENCE
statement must not cause the storage sequences of two different common blocks in the same program unit to be associated. See
Example 2.
An
EQUIVALENCE
statement must not cause a common block to be extended on the left-hand side. See Example 4.
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Examples
Example 1: Unlabeled common and labeled common:
DIMENSION V(100)
COMMON V, M
COMMON / LIMITS / I, J
…
In the above example,
V
and
M
are in the unlabeled common block;
I
and
J
are defined in the named common block,
LIMITS
.
Example 2: You cannot associate storage of two different common blocks in the same program unit:
COMMON /X/ A
COMMON /Y/ B
EQUIVALENCE ( A, B) !
←
Not allowed
Example 3: An
EQUIVALENCE
statement can extend a common block on the right-hand side:
DIMENSION A(5)
COMMON /X/ B
EQUIVALENCE ( B, A)
Example 4: An
EQUIVALENCE
statement must not cause a common block to be extended on the left-hand side:
COMMON /X/ A
REAL B(2)
EQUIVALENCE ( A, B(2))
! ←
Not allowed
Statements
109
4
4.12
COMPLEX
The
COMPLEX
statement specifies the type of a symbolic constant, variable, array, function, or dummy function to be complex, optionally specifies array dimensions and size, and initializes with values.
Syntax
COMPLEX [*
len
[,]] v [*
len
[/
c
/]] [, v [* l
en
[/
c
/]] …
v
Name of a symbolic constant, variable, array, array declarator, function, or dummy function
len c
Either 8, 16, or 32, the length in bytes of the symbolic constant, variable, array element, or function (32 is SPARC only)
List of constants for the immediately preceding name
Description
The declarations can be:
COMPLEX
,
COMPLEX*8
,
COMPLEX*16
, or
COMPLEX*32
.
COMPLEX
For a declaration such as
COMPLEX W
, the variable
W
is usually two
REAL*4 elements contiguous in memory, if no size options are set, interpreted as a complex number. Details are in “Default Size,” the next subsection.
COMPLEX*8
♦
For a declaration such as
COMPLEX*8 W
, the variable
W
is always two
REAL*4 elements contiguous in memory, interpreted as a complex number.
COMPLEX*16
♦
For a declaration such as
COMPLEX*16 W
,
W
is always two
REAL*8
elements contiguous in memory, interpreted as a double-width complex number.
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COMPLEX*32
♦
(SPARC only) For a declaration such as
COMPLEX*32 W
, the variable
W
is always two
REAL*16
elements contiguous in memory, interpreted as a quadruple-width complex number.
Default Size
If you specify the size as 8, 16, or 32,
COMPLEX*8
,
COMPLEX*16
,
COMPLEX*32
, you get what you specify; if you do not specify the size, you get the default size. (
*32 is for SPARC only.)
The default size, for a declaration such as
COMPLEX Z
, depends on
–r8
:
•
If the
–r8
option is on the f77
command line, then the compiler allocates 16 bytes, and does 16-byte arithmetic.
If
–r8
is not on the command line, the compiler allocates 8 bytes.
Similarly, for a declaration such as
DOUBLE COMPLEX Z
, the default size depends on the
–r8
option.
•
If
–r8
or
-dbl
is on the f77
command line, then the compiler allocates 32 bytes, and does 32-byte arithmetic (SPARC only).
If
–r8
or
-dbl
is not on the command line, the compiler allocates 16 bytes.
•
If you put both
–i2
and
–r8
on the f77
command line, the results are unpredictable.
Specifying the size is nonstandard. ♦
There is a double-complex version of each complex built-in function. Generally, the specific function names begin with
Z
or
CD
instead of
C
, except for the two functions
DIMAG
and
DREAL
, which return a real value.
There are specific complex functions for quad precision (SPARC only). In general, where there is a specific
REAL
a corresponding
COMPLEX
with a
C prefix, and a corresponding
COMPLEX DOUBLE
with a
CD
prefix, there is also a quad-precision
COMPLEX
function with a
CQ
prefix. Examples are:
SIN()
,
CSIN()
,
CDSIN()
,
CQSIN()
.
Statements
111
112
4
Examples
Example 1: Complex scalars. Styles. Each of these statements is equivalent to the others. (Don’t use all three statements in the same program unit—you cannot declare anything more than once in the same program unit.)
COMPLEX U, V
COMPLEX*8 U, V
COMPLEX U*8, V*8
Example 2: Initialize complex scalars:
COMPLEX U / (1, 9.0) /, V / (4.0, 5 ) /
A complex constant is a pair of numbers, either integers or reals.
Example 3: Double complex, some initialization:
COMPLEX R*16, V*16
COMPLEX U*16 / (1.0D0, 9 ) /, V*16 / (4.0, 5.0D0) /
COMPLEX*16 X / (1.0D0, 9.0) /, Y / (4.0D0, 5 ) /
A double-complex constant is a pair of numbers, and at least one number of the pair must be double precision.
Example 4: Quadruple complex, some initialization (SPARC only):
COMPLEX R*32, V*32
COMPLEX U*32 / (1.0Q0, 9 ) /, V*32 / (4.0, 5.0Q0) /
COMPLEX*32 X / (1.0Q0, 9.0) /, Y / (4.0Q0, 5 ) /
A quadruple complex constant is a pair of numbers, and at least one number of the pair must be quadruple precision.
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Example 5: Complex arrays, all of which are nonstandard:
COMPLEX R*16(5), S(5)*16 !
(SPARC only)
COMPLEX U*32(5), V(5)*32 !
(SPARC only)
COMPLEX X*8(5), Y(5)*8
4.13
CONTINUE
The
CONTINUE
statement is a “do-nothing” statement.
Syntax
[
label
] CONTINUE
label
Executable statement number
Description
The
CONTINUE
statement is often used as a place to hang a statement label, usually it is the end of a
DO
loop.
The
CONTINUE
statement is used primarily as a convenient point for placing a statement label, particularly as the terminal statement in a
DO
loop. Execution of a
CONTINUE
statement has no effect.
If the
CONTINUE
statement is used as the terminal statement of a
DO
loop, the next statement executed depends on the
DO
loop exit condition.
Statements
113
4
Example
DIMENSION U(100)
S = 0.0
DO 1 J = 1, 100
S = S + U(J)
IF ( S .GE. 1000000 ) GO TO 2
1 CONTINUE
STOP
2 CONTINUE
…
4.14
DATA
The
DATA
statement initializes variables, substrings, arrays, and array elements.
Syntax
DATA
nlist
/
clist
/ [[,]
nlist
/
clist
/] …
nlist clist
List of variables, arrays, array elements, substrings, and implied lists separated by commas
List of the form: c [,
c
] …
DO
c r
One of the forms: c or r*c, and
c is a constant or the symbolic name of a constant.
Nonzero, unsigned integer constant or the symbolic name of such constant
Description
All initially defined items are defined with the specified values when an executable program begins running.
r*c is equivalent to r successive occurrences of the constant c.
A
DATA
statement is a nonexecutable statement, and must appear after all specification statements, but it can be interspersed with statement functions and executable statements.
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Taking into account the repeat factor, the number of constants in clist must be equal to the number of items in the nlist. The appearance of an array in nlist is equivalent to specifying a list of all elements in that array. Array elements can be indexed by constant subscripts only.
Normal type conversion takes place for each noncharacter member of the clist.
Character Constants in the
DATA
Statement
If the length of a character item in nlist is greater than the length of the corresponding constant in clist, it is padded with blank characters on the right.
If the length of a character item in nlist is less than that of the corresponding constant in clist, the additional rightmost characters are ignored.
If the constant in clist is of integer type and the item of nlist is of character type, they must conform to the following rules:
•
The character item must have a length of one character.
•
The constant must be of type integer and have a value in the range 0 through 255. For
^A
,
^B
,
^C
, do not hold down the Control key and press A,
B, or C; use the
CHAR
intrinsic function.
If the constant of clist is a character constant or a Hollerith constant, and the item of nlist is of type
INTEGER
, then the number of characters that can be assigned is 2 or 4 for
INTEGER*2
and
INTEGER*4
respectively. If the character constant or the Hollerith constant has fewer characters than the capacity of the item, the constant is extended on the right with spaces. If the character or the
Hollerith constant contains more characters than can be stored, the constant is truncated on the right.
Implied
DO
Lists
An nlist can specify an implied
DO
list for initialization of array elements.
The form of an implied
DO
list is:
(dlist, iv
=
m1
,
m2
[,
m3
])
dlist
List of array element names and implied
DO
lists
iv
Integer variable, called the implied
DO
variable
Statements
115
116
4 m1 m2 m3
Integer constant expression specifying the initial value of iv
Integer constant expression specifying the limit value of iv
Integer constant expression specifying the increment value of iv. If m3 is omitted, then a default value of 1 is assumed.
The range of an implied
DO
loop is dlist. The iteration count for the implied
DO is computed from m1, m2, and m3, and it must be positive.
Variables
Variables can also be initialized in type statements. This is an extension of the
FORTRAN 77 Standard. Examples are given under each of the individual type statements and under the general type statement. ♦
Examples
Example 1: Character, integer, and real scalars. Real arrays:
&
&
&
CHARACTER TTL*16
REAL VEC(5), PAIR(2)
DATA TTL / 'Arbitrary Titles' /,
M / 9 /, N / 0 /,
PAIR(1) / 9.0 /,
VEC / 3*9.0, 0.1, 0.9 /
…
Example 2: Arrays—implied
DO
:
&
REAL R(3,2), S(4,4)
DATA ( S(I,I), I=1,4) / 4*1.0 /,
(( R(I,J), J=1,3), I=1,2) / 6*1.0 /
…
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Example 3: Mixing an integer and a character:
CHARACTER CR*1
INTEGER I*2, N*4
DATA I / 'oy' /, N / 4Hs12t /, CR / 13 /
…
4.15
DECODE
/
ENCODE
ENCODE
writes to a character variable, array, or array element. ♦
DECODE reads from a character variable, array, or array element. ♦ Data is edited according to the format identifier.
Similar functionality can be accomplished, using internal files with formatted sequential
WRITE
statements and
READ
statements.
ENCODE
and
DECODE
are not in the FORTRAN 77 Standard, and are provided for compatibility with older versions of FORTRAN 77.
Syntax f
ENCODE(
size
,
f, buf
[, IOSTAT=
ios
] [, ERR
= s
] ) [
iolist
]
DECODE(
size
,
f
,
buf
[, IOSTAT=
ios
] [, ERR=
s
] ) [
iolist
]
size
Number of characters to be translated, an integer expression
Format identifier, either the label of a
FORMAT
statement, or a character expression specifying the format string, or an asterisk.
buf ios
Variable, array, or array element
I/O status specifier, ios must be an integer variable or an integer array element.
s
The error specifier (statement label) s must be the label of executable statement in the same program unit in which the
ENCODE
and
DECODE statement occurs.
iolist
List of input/output items.
Statements
117
118
4
Description
The entities in the I/O list must be one of the following:
•
Variables
•
Substrings
•
Arrays
•
Array elements
•
Record fields
A simple unsubscripted array name specifies all of the elements of the array in memory storage order, with the leftmost subscript increasing more rapidly.
Execution proceeds as follows:
1. The
ENCODE
statement translates the list items to character form according to the format identifier, and stores the characters in buf. A
WRITE
operation on internal files does the same.
2. The
DECODE
statement translates the character data in buf to internal
(binary) form according to the format identifier, and stores the items in the list. A
READ
statement does the same.
3. If buf is an array, its elements are processed in the order of subscript progression, with the leftmost subscript increasing more rapidly.
4. The number of characters that an
ENCODE
or a
DECODE
statement can process depends on the data type of buf. For example, an
INTEGER*2
array can contain two characters per element, so that the maximum number of characters is twice the number of elements in that array. A character variable or character array element can contain characters equal in number to its length. A character array can contain characters equal in number to the length of each element multiplied by the number of elements.
5. The interaction between the format identifier and the I/O list is the same as for a formatted I/O statement.
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Example
A program using
DECODE/ENCODE
:
CHARACTER S*6 / '987654' /, T*6
INTEGER V(3)*4
DECODE( 6, '(3I2)', S ) V
WRITE( *, '(3I3)') V
ENCODE( 6, '(3I2)', T ) V(3), V(2), V(1)
PRINT *, T
END
The above program has this output:
98 76 54
547698
The
DECODE
reads the characters of
S
as 3 integers, and stores them into
V(1)
,
V(2)
, and
V(3)
.
The
ENCODE
statement writes the values
V(3)
,
V(2)
, and
V(1)
into
T
as characters;
T
then contains
'547698'
.
4.16
DIMENSION
The
DIMENSION
statement specifies the number of dimensions for an array, including the number of elements in each dimension.
Optionally, the
DIMENSION
statement initializes items with values.
Statements
119
4
120
Syntax
DIMENSION
a ( d ) [,a ( d
)] …
a d
Name of an array
Specifies the dimensions of the array. It is a list of 1 to 7 declarators separated by commas.
Description
This section contains descriptions for the dimension declarator and the arrays.
Dimension Declarator
The lower and upper limits of each dimension are designated by a dimension declarator. The form of a dimension declarator is:
[
dd1
:]
dd2
dd1 and dd2 are dimension bound expressions specifying the lower- and upperbound values. They can be arithmetic expressions of type integer or real. They can be formed using constants, symbolic constants, formal arguments, or variables defined in the
COMMON
statement. Array references and references to user-defined functions cannot be used in the dimension bound expression. dd2 can also be an asterisk. If dd1 is not specified, a value of one is assumed. The value of dd1 must be less than or equal to dd2.
Nonconstant dimension-bound expressions can be used in a subprogram to define adjustable arrays, but not in a main program.
Noninteger dimension bound expressions are converted to integers before use.
Any fractional part is truncated.
Adjustable Array
If the dimension declarator is an arithmetic expression that contains formal arguments or variables defined in the
COMMON
statement, then the array is called an adjustable array. In such cases, the dimension is equal to the initial value of the argument upon entry into the subprogram.
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Assumed-Size Array
The array is called an assumed-size array when the dimension declarator contains an asterisk. In such cases, the upper bound of that dimension is not stipulated. An asterisk can only appear for formal arrays and as the upper bound of the last dimension in an array declarator.
Examples
Example 1: Arrays in a main program:
DIMENSION M(4,4), V(1000)
…
END
In the above example,
M
is specified as an array of dimensions 4
×
4 and
V
is specified as an array of dimension 1000.
Example 2: An adjustable array in a subroutine:
SUBROUTINE INV( M, N )
DIMENSION M( N, N )
…
END
In the above example, the formal arguments are an array,
M
, and a variable
N
.
M is specified to be a square array of dimensions
N
×
N
.
Example 3: Lower and upper bounds:
DIMENSION HELIO (-3:3, 4, 3:9)
…
END
In the above example,
HELIO
is a 3-dimensional array. The first element is
HELIO(-3,1,3)
and the last element is
HELIO(3,4,9)
.
Statements
121
4
Example 4: Dummy array with lower and upper bounds:
SUBROUTINE ENHANCE( A, NLO, NHI )
DIMENSION A(NLO : NHI)
…
END
Example 5: Noninteger bounds:
PARAMETER ( LO = 1, HI = 9.3 )
DIMENSION A(HI, HI*3 + LO )
…
END
In the above example,
A
is an array of dimension 9
×
28.
Example 6: Adjustable array with noninteger bounds:
SUBROUTINE ENHANCE( A, X, Y )
DIMENSION A(X : Y)
…
END
4.17
DO
Syntax
The
DO
statement repeatedly executes a set of statements.
DO
s
[,]
loop-control
or
DO
loop-control ♦
s is a statement number.
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The form of loop-control is:
variable = e1, e2 [, e3 ]
variable
e1, e2, e3
Variable of type integer, real, or double precision.
Expressions of type integer, real or double precision, specifying initial, limit, and increment values respectively.
Description
The
DO
statement contains the following constructs.
Labeled
DO
Loop
A labeled
DO
loop consists of the following:
•
DO
statement
•
Set of executable statements called a block
•
Terminal statement, usually a
CONTINUE
statement
Terminal Statement
The statement identified by s is called the terminal statement. It must follow the
DO
statement in the sequence of statements within the same program unit as the
DO
statement.
The terminal statement should not be one of the following statements:
•
Unconditional
GO TO
•
Assigned
GO TO
•
Arithmetic
IF
•
Block
IF
•
ELSE IF
•
ELSE
•
END IF
•
RETURN
•
STOP
•
END DO
Statements
123
4
124
If the terminal statement is a logical
IF
statement, it can contain any executable statement, except:
•
DO
•
DO WHILE
•
Block
IF
•
ELSE IF
•
ELSE
•
END IF
•
END
•
Logical
IF
statement
DO
Loop Range
The range of a
DO
loop consists of all of the executable statements that appear following the
DO
statement, up to and including the terminal statement.
If a
DO
statement appears within the range of another
DO
loop, its range must be entirely contained within the range of the outer
DO
loop. More than one labeled
DO
loop can have the same terminal statement.
If a
DO
statement appears within an
IF
,
ELSE IF
, or
ELSE
block, the range of the associated
DO
loop must be contained entirely within that block.
If a block
IF
statement appears within the range of a
DO
loop, the corresponding
END IF
statement must also appear within the range of that
DO loop.
Block
DO
Loop
♦
A block
DO
loop consists of:
•
DO
statement
•
Set of executable statements called a block
•
Terminal statement, an
END DO
statement
This loop is nonstandard.
Execution proceeds as follows:
1. The expressions e1, e2, and e3 are evaluated. If e3 is not present, its value is assumed to be one.
FORTRAN 77 Reference Manual
4
2. The
DO
variable is initialized with the value of e1.
3. The iteration count is established as the value of the expression:
MAX (INT ((
e2
-
e1
+
e3
) /
e3
), 0)
The iteration count is zero if either of the following is true:
•
e1
>
e2 and e3
>
zero.
•
e1
<
e2 and e3
<
zero.
If the
–onetrip
compile time option is specified, then the iteration count is never less than one.
4. The iteration count is tested, and, if it is greater than zero, the range of the
DO
loop is executed.
Terminal Statement Processing
After the terminal statement of a
DO
loop is executed, the following steps are performed:
1. The value of the
DO
variable, if any, is incremented by the value of e3 that was computed when the
DO
statement was executed.
2. The iteration count is decreased by one.
3. The iteration count is tested, and if it is greater than zero, the statements in the range of the
DO
loop are executed again.
Restrictions
The
DO
variable must not be modified in any way within the range of the
DO loop.
You must not jump into the range of a
DO
loop from outside its range.
Statements
125
126
4
Comments
In some cases, the
DO
variable can overflow as a result of an increment that is performed prior to testing it against the final value. When this happens, your program has an error, and neither the compiler nor the runtime system detects it. In this situation, though the
DO
variable wraps around, the loop can terminate properly.
If there is a jump into the range of a
DO
loop from outside its range, a warning is issued, but execution continues anyway.
When the jump is from outside to the terminal statement that is
CONTINUE
, and this statement is the terminal statement of several nested
DO
loops, then the most inner
DO
loop is always executed.
Examples
Example 1: Nested
DO
loops:
N = 0
DO 210 I = 1, 10
J = I
DO 200 K = 5, 1
L = K
200
N = N + 1
CONTINUE
210 CONTINUE
WRITE(*,*)'I =',I, ', J =',J, ', K =',K, ', N =',N, ', L =',L
END demo% f77 -silent DoNest1.f
"DoNest1.f", line 4: Warning: DO range never executed demo% a.out
I = 11, J = 10, K = 5, N = 0, L = 0 demo%
The inner loop is not executed, and at the
WRITE
,
L
is undefined. Here
L
is shown as 0, but that is implementation-dependent; do not rely on it.
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Example 2: The program
DoNest2.f
(
DO
variable always defined):
INTEGER COUNT, OUTER
COUNT = 0
DO OUTER = 1, 5
NOUT = OUTER
DO INNER = 1, 3
NIN = INNER
COUNT = COUNT+1
END DO
END DO
WRITE(*,*) OUTER, NOUT, INNER, NIN, COUNT
END
The above program prints out:
6 5 4 3 15
4.18
DO WHILE
The
DO WHILE
♦ statement repeatedly executes a set of statements while the specified condition is true.
Syntax
DO [
s
[,]] WHILE (
e
) s Label of an executable statement e Logical expression
Description
Execution proceeds as follows:
1. The specified expression is evaluated.
2. If the value of the expression is true, the statements in the range of the
DO
WHILE
loop are executed.
Statements
127
4
128
3. If the value of the expression is false, control is transferred to the statement following the
DO WHILE
loop.
Terminal Statement
If s is specified, the statement identified by it is called the terminal statement, and it must follow the
DO WHILE
statement. The terminal statement must not be one of the following statements:
•
Unconditional
GO TO
•
Assigned
GO TO
•
Arithmetic
IF
•
Block
IF ELSE IF
•
ELSE
•
END IF
•
RETURN
•
STOP
•
END
•
DO
•
DO WHILE
If the terminal statement is a logical
IF
statement, it can contain any executable statement, except:
•
DO
•
DO WHILE
•
Block
IF
•
ELSE IF
•
ELSE
•
END IF
•
END
•
Logical
IF
If s is not specified, the
DO WHILE
loop must end with an
END DO
statement.
DO WHILE
Loop Range
The range of a
DO WHILE
loop consists of all the executable statements that appear following the
DO WHILE
statement, up to and including the terminal statement.
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Restrictions
If you jump into the range of a
DO WHILE
loop from outside its range, then the results are unpredictable.
Comments
If a
DO WHILE
statement appears within the range of another
DO WHILE
loop, its range must be entirely contained within the range of the outer
DO WHILE loop. More than one
DO WHILE
loop can have the same terminal statement.
If a
DO WHILE
statement appears within an
IF
,
ELSE IF
, or
ELSE
block, the range of the associated
DO WHILE
loop must be entirely within that block.
If a block
IF
statement appears within the range of a
DO WHILE
loop, the corresponding
END IF
statement must also appear within the range of that
DO
WHILE
loop.
Terminal Statement Processing
After the terminal statement of a
DO WHILE
loop is executed, control is transferred back to the corresponding
DO WHILE
statement.
The variables used in the e can be modified in any way within the range of the
DO WHILE
loop.
Examples
Example 1: A
DO WHILE
without a statement number:
INTEGER A(4,4), C, R
…
C = 4
R = 1
DO WHILE ( C .GT. R )
A(C,R) = 1
C = C - 1
END DO
Statements
129
4
Example 2: A
DO WHILE
with a statement number:
INTEGER A(4,4), C, R
…
DO 10 WHILE ( C .NE. R )
A(C,R) = A(C,R) + 1
C = C+1
10 CONTINUE
4.19
DOUBLE COMPLEX
The
DOUBLE COMPLEX
♦ statement specifies the type to be double complex. It optionally specifies array dimensions and size, and initializes with values.
Syntax v c
DOUBLE COMPLEX
v
[/
c
/] [,
v
[/
c
/] …
Name of a symbolic constant, variable, array, array declarator, function, or dummy function
List of constants for the immediately preceding name
Description
The declaration can be:
DOUBLE COMPLEX
or
COMPLEX*16
.
DOUBLE COMPLEX
♦
For a declaration such as
DOUBLE COMPLEX Z
, the variable
Z
is usually two
REAL*8
elements contiguous in memory, if no size options are set, interpreted as one double-width complex number. See the next subsection, “Default Size.”
COMPLEX*16
♦
For a declaration such as
COMPLEX*16 Z
, the variable
Z
is always two
REAL*8
elements contiguous in memory, interpreted as one double-width complex number.
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Default Size
If you explicitly specify the size as 16,
COMPLEX*16
, you get what you specify; if you do not specify the size, you get the default size. Default size, for such a declaration as
DOUBLE COMPLEX Z
, depends on
–r8
.
•
If
–r8
or
-dbl
is on the f77
command line, then the compiler allocates 32 bytes, and does 128-bit arithmetic (SPARC only).
•
If
–r8
or
-dbl
is not on the command line, then the compiler allocates 16 bytes, and does 64-bit arithmetic.
•
If you put both
–i2
and
–r8
on the f77
command line, the results are unpredictable.
Comments
There is a double-complex version of each complex built-in function. Generally, the specific function names begin with
Z
or
CD
instead of
C
, except for the two functions,
DIMAG
and
DREAL
, which return a real value. Examples are:
SIN()
,
CSIN()
,
CDSIN()
.
Example: Double-complex scalars and arrays:
DOUBLE COMPLEX U, V
DOUBLE COMPLEX W(3,6)
COMPLEX*16 X, Y(5,5)
COMPLEX U*16(5), V(5)*16
4.20
DOUBLE PRECISION
The
DOUBLE PRECISION
statement specifies the type to be double precision, and optionally specifies array dimensions and initializes with values.
Statements
131
4
132
Syntax v c
DOUBLE PRECISION
v
[/
c
/] [,
v
[/
c
/] …
Name of a symbolic constant, variable, array, array declarator, function, or dummy function
List of constants for the immediately preceding name
Description
The declaration can be:
DOUBLE PRECISION
or
REAL*8
.
DOUBLE PRECISION
For a declaration such as
DOUBLE PRECISION X
, the variable
X
is usually a
REAL*8
element in memory, interpreted as one double-width real number. See the next subsection, “Default Size.”
REAL*8
♦
For a declaration such as
REAL*8 X
, the variable
X
is always an element of type
REAL*8
in memory, interpreted as a double-width real number.
Default Size
If you explicitly specify the size as 8,
REAL*8
, you get what you specify; if you do not specify the size, you get the default size.
The default size for a declaration such as
DOUBLE PRECISION X
depends on the
–r8
option, as follows:
•
If
–r8
is on the f77
command line, then the compiler allocates 16 bytes, and does 128-bit arithmetic (SPARC only).
•
If
–r8
is not on the command line, then the compiler allocates 8 bytes, and does 64-bit arithmetic.
•
If you put both
–i2
and
–r8
on the f77
command line, the results are unpredictable.
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4
Example
Example: Double-precision scalars and arrays:
DOUBLE PRECISION R, S
DOUBLE PRECISION T(3,6)
REAL*8 U(3,6)
REAL V*8(6), W(6)*8
4.21
ELSE
The
ELSE
statement indicates the beginning of an
ELSE
block.
Syntax
IF (
e
) THEN
...
ELSE
...
END IF
e
Logical expression
Description
Execution of an
ELSE
statement has no effect on the program.
An
ELSE
block consists of all the executable statements following the
ELSE statements, up to but not including the next
END IF
statement at the same
IF level as the
ELSE
statement. See Section 4.40, “IF (Block),” for more details.
An
ELSE
block can be empty.
Restrictions
You cannot jump into an
ELSE
block from outside the
ELSE
block.
The statement label, if any, of an
ELSE
statement cannot be referenced by any statement.
Statements
133
4
A matching
END IF
statement of the same
IF
level as the
ELSE
must appear before any
ELSE IF
or
ELSE
statement at the same
IF
level.
Examples
Example 1:
ELSE
:
CHARACTER S
…
IF ( S .GE. '0' .AND. S .LE. '9' ) THEN
CALL PUSH
ELSE
CALL TOLOWER
END IF
…
Example 2: An invalid
ELSE IF
where an
END IF
is expected:
IF ( K .GT. 5 ) THEN
ELSE
N = 1
N = 0
ELSE IF ( K .EQ. 5 ) THEN
←
Incorrect
…
4.22
ELSE IF
The
ELSE IF
provides a multiple alternative decision structure.
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Syntax
IF (
e1
) THEN
ELSE IF (
e2
) THEN
END IF…
e1 and e2 Logical expressions
Description
You can make a series of independent tests, and each test can have its own sequence of statements.
An
ELSE IF
block consists of all the executable statements following the
ELSE
IF
statement up to, but not including, the next
ELSE IF
,
ELSE
, or
END IF statement at the same
IF
level as the
ELSE IF
statement.
An
ELSE IF
block can be empty.
Execution of the
ELSE IF
proceeds as follows:
1. e is evaluated.
2. If e is true, execution continues with the first statement of the
ELSE IF
block. If e is true and the
ELSE IF
block is empty, control is transferred to the next
END IF
statement at the same
IF
level as the
ELSE IF
statement.
3. If e is false, control is transferred to the next
ELSE IF
,
ELSE
, or
END IF
statement at the same
IF
level as the
ELSE IF
statement.
Restrictions
You cannot jump into an
ELSE IF block from outside the
ELSE IF
block.
The statement label, if any, of an
ELSE IF
statement cannot be referenced by any statement.
A matching
END IF
statement of the same
IF
level as the
ELSE IF
must appear before any
ELSE IF
or
ELSE
statement at the same
IF
level.
Statements
135
4
Example
Example:
ELSE IF
:
READ (*,*) N
IF ( N .LT. 0 ) THEN
WRITE(*,*) 'N<0'
ELSE IF ( N .EQ. 0) THEN
WRITE(*,*) ’N=0’
ELSE
WRITE(*,*) ’N>0’
END IF
4.23
ENCODE
/
DECODE
The
ENCODE
♦ statement writes data from a list to memory.
Syntax
ENCODE(
size
,
f
,
buf
[, IOSTAT=
ios
] [, ERR=
s
] ) [
iolist
]
size
Number of characters to be translated
f buf
Format identifier
Variable, array, or array element
ios s iolist
I/O status specifier
Error specifier (statement label)
List of I/O items, each a character variable, array, or array element
Description
ENCODE
is provided for compatibility with older versions of FORTRAN 77.
Similar functionality can be accomplished using internal files with a formatted sequential
WRITE
statement.
ENCODE
is not in the FORTRAN 77 Standard.
Data are edited according to the format identifier.
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4
Example
CHARACTER S*6, T*6
INTEGER V(3)*4
DATA S / '987654' /
DECODE( 6, 1, S ) V
1 FORMAT( 3 I2 )
ENCODE( 6, 1, T ) V(3), V(2), V(1)
The
DECODE
reads the characters of
S
as 3 integers, and stores them into
V(1)
,
V(2)
, and
V(3)
. The
ENCODE
statement writes the values
V(3)
,
V(2)
, and
V(1)
, into
T
as characters;
T
then contains
'547698'
.
See Section 4.15, “DECODE/ENCODE,” for more details and a full example.
4.24
END
The
END
statement indicates the end of a program unit.
Syntax
END
Description
The
END
statement:
•
Must be the last statement in the program unit.
•
Must be the only statement in a line.
•
Can have a label.
In a main program, an
END
statement terminates the execution of the program.
In a function or subroutine, it has the effect of a
RETURN
. ♦
In the FORTRAN 77 Standard, the
END
statement cannot be continued, but f77 allows this practice. ♦
No other statement, such as an
END IF
statement, can have an initial line that appears to be an
END
statement.
Statements
137
4
Example
Example:
END
:
PROGRAM MAIN
WRITE( *, * ) 'Very little'
END
4.25
END DO
The
END DO
statement terminates a
DO
loop. ♦
Syntax
END DO
Description
The
END DO
statement is the delimiting statement of a Block
DO
statement. If the statement label is not specified in a
DO
statement, the corresponding terminating statement must be an
END DO
statement. You can branch to an
END
DO
statement only from within the range of the
DO
loop that it terminates.
Examples
Example 1: A
DO
loop with a statement number:
DO 10 N = 1, 100
…
10 END DO
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Example 2: A
DO
loop without statement number:
DO N = 1, 100
…
END DO
4.26
END FILE
The
END FILE
statement writes an end-of-file record as the next record of the file connected to the specified unit.
Syntax
END FILE
u
END FILE ( [ UNIT= ]
u
[, IOSTAT=
ios
] [, ERR= s ])
u
Unit identifier of an external unit connected to the file, The options can be specified in any order, but if
UNIT=
is omitted, then u must be first.
ios s
I/O status specifier, an integer variable or an integer array element.
Error specifier, s must be the label of an executable statement in the same program in which the
END FILE
statement occurs. The program control is transferred to the label in the event of an error during the execution of the
END FILE
statement.
Description
If you are using the
ENDFILE
statement and other standard FORTRAN 77 I/O for tapes, we recommend that you use the
TOPEN()
routines instead, because they are more reliable.
Two endfile records signify the end-of-tape mark. When writing to a tape file,
ENDFILE
writes two endfile records, then the tape backspaces over the second one. If the file is closed at this point, both end-of-file and end-of-tape are marked. If more records are written at this point, either by continued write statements or by another program if you are using no-rewind magnetic tape, the first tape mark stands (endfile record), and is followed by another data file, then by more tape marks, and so on.
Statements
139
4
Restrictions
u must be connected for sequential access. Execution of an
END FILE
statement on a direct-access file is not defined in the FORTRAN 77 Standard, and is unpredictable. Do not use an
END FILE
statement on a direct-access file.
Examples
Example 1: Constants:
END FILE 2
END FILE ( 2 )
END FILE ( UNIT=2 )
Example 2: Variables:
LOGUNIT = 2
END FILE LOGUNIT
END FILE ( LOGUNIT )
END FILE ( UNIT=LOGUNIT )
Example 3: Error trap:
NOUT = 2
END FILE ( UNIT=NOUT, IOSTAT=KODE, ERR=9)
…
9 WRITE(*,*) 'Error at END FILE, on unit', NOUT
STOP
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4.27
END IF
The
END IF
statement ends the block
IF
that the
IF
began.
Syntax
END IF
Description
For each block
IF
statement there must be a corresponding
END IF
statement in the same program unit. An
END IF
statement matches if it is at the same
IF level as the block
IF
statement.
Examples
Example 1:
IF/END IF
:
IF ( N .GT. 0 )THEN
N = N+1
END IF
Example 2:
IF/ELSE/END IF
:
IF ( N .EQ. 0 ) THEN
N = N+1
ELSE
N = N-1
END IF
Statements
141
4
4.28
END MAP
The
END MAP
♦ statement terminates the
MAP
declaration.
Syntax
END MAP
Description
See Section 4.70, “UNION and MAP.”
Restrictions
The
MAP
statement must be within a
UNION
statement.
Example
…
MAP
CHARACTER *16 MAJOR
END MAP
…
4.29
END STRUCTURE
The END STRUCTURE
♦ statement t erminates the
STRUCTURE
statement.
Syntax
END STRUCTURE
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Description
See Section 4.66, “STRUCTURE.”
Example
STRUCTURE /PROD/
INTEGER*4 ID
CHARACTER*16 NAME
CHARACTER*8
REAL*4
REAL*4
END STRUCTURE
MODEL
COST
PRICE
4.30
END UNION
The
END UNION
♦ statement terminates the
UNION
statement.
Syntax
END UNION
Description
See Section 4.70, “UNION and MAP.”
4
Statements
143
4
Example
UNION
MAP
CHARACTER*16
END MAP
MAP
INTEGER*2 CREDITS
CHARACTER *8 GRAD_DATE
END MAP
END UNION
4.31
ENTRY
The
ENTRY
statement defines an alternate entry point within a subprogram.
Syntax
ENTRY
en
[ ( [
fa
[,
fa
] … ] ) ]
en
Symbolic name of an entry point in a function or subroutine subprogram
fa
Formal argument—it can be a variable name, array name, formal procedure name, or an asterisk specifying an alternate return label.
Description
Note these nuances for the
ENTRY
statement:
Procedure References by Entry Names
An
ENTRY
name used in a subroutine subprogram is treated like a subroutine and can be referenced with a
CALL
statement. Similarly, the
ENTRY
name used in a function subprogram is treated like a function and can be referenced as a function reference.
An entry name can be specified in an
EXTERNAL
statement and used as an actual argument. It cannot be used as a dummy argument.
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4
Execution of an
ENTRY
subprogram (subroutine or function) begins with the first executable statement after the
ENTRY
statement.
The
ENTRY
statement is a nonexecutable statement.
The entry name cannot be used in the executable statements that physically precede the appearance of the entry name in an
ENTRY
statement.
Parameter Correspondence
The formal arguments of an
ENTRY
statement need not be the same in order, number, type, and name as those for
FUNCTION
,
SUBROUTINE
, and other
ENTRY
statements in the same subprogram. Each reference to a function, subroutine, or entry must use an actual argument list that agrees in order, number, type, and name with the dummy argument list in the corresponding
FUNCTION
,
SUBROUTINE
, or
ENTRY
statement.
Alternate return arguments in
ENTRY
statements can be specified by placing asterisks in the dummy argument list. Ampersands are valid alternates. ♦
ENTRY
statements that specify alternate return arguments can be used only in subroutine subprograms, not functions.
Restrictions
An
ENTRY
statement cannot be used within a block
IF
construct or a
DO
loop.
If an
ENTRY
statement appears in a character function subprogram, it must be defined as type
CHARACTER
with the same length as that of a function subprogram.
Statements
145
146
4
Examples
Example 1: Multiple entry points in a subroutine:
SUBROUTINE FINAGLE( A, B, C )
INTEGER A, B
CHARACTER C*4
…
RETURN
ENTRY SCHLEP( A, B, C )
…
RETURN
ENTRY SHMOOZ
…
RETURN
END
In the above example, the subroutine
FINAGLE
has two alternate entries: the entry
SCHLEP
has an argument list; the entry
SHMOOZ
has no argument list.
Example 2: In the calling routine, you can call the above subroutine and entries as follows:
INTEGER A, B
CHARACTER C*4
…
CALL FINAGLE( A, B, C )
…
CALL SHMOOZ
…
CALL SCHLEP( A, B, C )
…
In the above example, the order of the call statements need not match the order of the entry statements.
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4
Example 3: Multiple entry points in a function:
REAL FUNCTION F2 ( X )
F2 = 2.0 * X
RETURN
ENTRY F3 ( X )
F3 = 3.0 * X
RETURN
ENTRY FHALF ( X )
FHALF = X / 2.0
RETURN
END
4.32
EQUIVALENCE
The
EQUIVALENCE
statement specifies that two or more variables or arrays in a program unit share the same memory.
Syntax
EQUIVALENCE (
nlist
) [, (
nlist
) ] …
nlist
List of variable names, array element names, array names, and character substring names separated by commas
Description
An
EQUIVALENCE
statement stipulates that the storage sequence of the entities whose names appear in the list nlist must have the same first memory location.
An
EQUIVALENCE
statement can cause association of entities other than specified in the nlist.
An array name, if present, refers to the first element of the array.
If an array element name appears in an
EQUIVALENCE
statement, the number of subscripts can be less than or equal to the number of dimensions specified in the array declarator for the array name.
Statements
147
4
Restrictions
In nlist, dummy arguments and functions are not permitted.
Subscripts of array elements must be integer constants greater than the lower bound and less than or equal to the upper bound.
EQUIVALENCE
can associate automatic variables only with other automatic variables or undefined storage classes. These classes must be ones which are not in any of the
COMMON
,
STATIC
,
SAVE
,
DATA
, or dummy arguments.
An
EQUIVALENCE
statement can associate an element of type character with a noncharacter element. ♦
An
EQUIVALENCE
statement cannot specify that the same storage unit is to occur more than once in a storage sequence. For example, the following statement is not allowed:
DIMENSION A (2)
EQUIVALENCE (A(1),B), (A(2),B)
An
EQUIVALENCE
statement cannot specify that consecutive storage units are to be nonconsecutive. For example, the following statement is not allowed:
REAL A (2)
DOUBLE PRECISION D (2)
EQUIVALENCE (A(1), D(1)), (A(2), D(2))
When
COMMON
statements and
EQUIVALENCE
statements are used together, several additional rules can apply. For such rules, refer to the notes on the
COMMON
statement.
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Example
CHARACTER A*4, B*4, C(2)*3
EQUIVALENCE (A,C(1)),(B,C(2))
B
C
The association of
A
,
B
, and
C
can be graphically illustrated as follows.
01 02 03 04 05 06 07
A A(1) A(2) A(3) A(4)
C(1)
B(1) B(2)
C(2)
B(3) B(4)
4.33
EXTERNAL
The
EXTERNAL
statement specifies procedures or dummy procedures as external, and allows their symbolic names to be used as actual arguments.
Syntax
EXTERNAL
proc
[,
proc
] …
proc
Name of external procedure, dummy procedure, or block data routine.
Description
If an external procedure or a dummy procedure is an actual argument, it must be in an
EXTERNAL
statement in the same program unit.
If an intrinsic function name appears in an
EXTERNAL
statement, that name refers to some external subroutine or function. The corresponding intrinsic function is not available in the program unit.
Statements
149
150
4
Restrictions
A subroutine or function name can appear in only one of the
EXTERNAL statements of a program unit.
A statement function name must not appear in an
EXTERNAL
statement.
Examples
Example 1: Use your own version of
TAN
:
EXTERNAL TAN
T = TAN( 45.0 )
…
END
FUNCTION TAN( X )
…
RETURN
END
Example 2: Pass a user-defined function name as an argument:
REAL AREA, LOW, HIGH
EXTERNAL FCN
…
CALL RUNGE ( FCN, LOW, HIGH, AREA )
…
END
FUNCTION FCN( X )
…
RETURN
END
SUBROUTINE RUNGE ( F, X0, X1, A )
…
RETURN
END
FORTRAN 77 Reference Manual
4
4.34
FORMAT
Syntax
The
FORMAT
statement specifies the layout of the input or output records.
label
FORMAT (
f
)
f label
Statement number
Format specification list
The items in f have the form:
r d
[
r
]
d
[
r
] (
f
)
A repeat factor
An edit descriptor (repeatable or nonrepeatable). If r is present, then d must be repeatable.
The repeatable edit descriptors are:
I
I
w
I
w.m
O
O
w
O
w.m
Z
Z
w
Z
w.m
F
F
w
F
w.m
A
A
w
L
L
w
E
E
w
E
w.m
E
w.m.e
E
w.mEe
D
D
w
D
w.m
D
w.m.e
D
w.mEe
G
G
w
G
w.m
G
w.m.e
G
w.m
E
e
Here is a summary:
•
I
,
O
,
Z
are for integers (decimal, octal, hex)
•
F
,
E
,
D
,
G
are for reals (fixed-point, exponential, double, general)
•
A
is for characters
•
L
is for logicals
Statements
151
152
4
See the section,“Formatted I/O,” in Chapter 5, “Input and Output,” for full details of these edit descriptors.
Nonrepeatable Edit Descriptors
:
/
B
BN
BZ
'a1a2 … an'
"a1a2 … an"
nHa1a2 … an
$
SP
SS
Tn
nT
[k]R
[k]P
S
SU
TL[n]
TR[n]
[n]X
k defaults to 10
k defaults to 0
n defaults to 1
n defaults to 1
n defaults to 1
Variable Format Expressions ♦
In general, any integer constant in a format can be replaced by an arbitrary expression enclosed in angle brackets:
1 FORMAT( … <
e
> … )
The n in an n
H
… edit descriptor cannot be a variable format expression.
Description
The
FORMAT
statement includes the explicit editing directives to produce or use the layout of the record. It is used with formatted input/output statements and
ENCODE/DECODE
statements.
FORTRAN 77 Reference Manual
4
Repeat Factor
r must be a nonzero, unsigned, integer constant.
Repeatable Edit Descriptors
The descriptors
I
,
O
,
Z
,
F
,
E
,
D
,
G
,
L
, and
A
indicate the manner of editing and are repeatable.
w and e are nonzero, unsigned integer constants.
d and m are unsigned integer constants.
Nonrepeatable Edit Descriptors
The descriptors are the following:
(")
,
($)
,
(')
,
(/)
,
(:)
,
B
,
BN
,
BZ
,
H
,
P
,
R
,
Q
,
S
,
SU
,
SP
,
SS
,
T
,
TL
,
TR
,
X
These descriptors indicate the manner of editing and are not repeatable:
•
Each ai is any ASCII character.
•
n is a nonzero, unsigned integer constant.
•
k is an optionally signed integer constant.
Item Separator
Items in the format specification list are separated by commas. A comma can be omitted before or after the slash and colon edit descriptors, between a
P
edit descriptor, and the immediately following
F, E, D,
or
G
edit descriptors.
In some sense, the comma can be omitted anywhere the meaning is clear without it, but, other than those cases listed above, this is nonstandard.
◆
Restrictions
The
FORMAT
statement label cannot be used in a
GO TO
,
IF
-arithmetic,
DO
, or alternate return.
Statements
153
4
Warnings
For constant formats, invalid format strings cause warnings or error messages at compile time.
For formats in variables, invalid format strings cause warnings or error messages at runtime.
For variable format expressions, of the form
<e>
, invalid format strings cause warnings or error messages at compile time or runtime.
See Chapter 5, “Input and Output,” for more details and more examples.
Examples
Example 1: Some
A
,
I
, and
F
formats:
READ( 2, 1 ) PART, ID, HEIGHT, WEIGHT
1 FORMAT( A8, 2X, I4, F8.2, F8.2 )
WRITE( 9, 2 ) PART, ID, HEIGHT, WEIGHT
2 FORMAT( 'Part:', A8, ' Id:', I4, ' Height:', F8.2,
& ' Weight:', F8.2 )
Example 2: Variable format expressions:
DO 100 N = 1, 50
…
1 FORMAT( 2X, F<N+1>.2 )
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4.35
FUNCTION
(External)
The
FUNCTION
statement identifies a program unit as a function subprogram.
Syntax
[
type
] FUNCTION
fun
( [
ar
[,
ar
] … ] )
BYTE
♦
CHARACTER
CHARACTER*
n
CHARACTER*(*)
COMPLEX
COMPLEX*8
COMPLEX*16
♦
♦
COMPLEX*32
♦
(SPARC only)
n (as in CHARACTER*n)
fun ar
type is one of the following:
DOUBLE COMPLEX
♦
DOUBLE PRECISION
INTEGER
INTEGER*2
INTEGER*4
INTEGER*8
LOGICAL
♦
♦
♦
LOGICAL*1
LOGICAL*2
LOGICAL*4
LOGICAL*8
♦
♦
♦
♦
REAL
REAL*4
REAL*8
REAL*16
♦
♦
♦
(SPARC only)
Must be greater than zero
Symbolic name assigned to function
Formal argument name
An alternate nonstandard syntax for length specifier is as follows: ♦
[
type
] FUNCTION
name
[*
m
]([
ar
[,
ar
] …])
m
Unsigned, nonzero integer constant specifying length of the data type.
Description
Note the type, value, and formal arguments for a
FUNCTION
statement.
Type of Function
The function statement involves type, name, and formal arguments.
Statements
155
4
If type is not present in the
FUNCTION
statement, then the type of the function is determined by default and by any subsequent
IMPLICIT
or type statement.
If type is present, then the function name cannot appear in other type statements.
Value of Function
The symbolic name of the function must appear as a variable name in the subprogram. The value of this variable, at the time of execution of the
RETURN or
END
statement in the function subprogram, is the value of the function.
Formal Arguments
The list of arguments defines the number of formal arguments. The type of these formal arguments is defined by some combination of default, type statements,
IMPLICIT
statements, and
DIMENSION
statements.
The number of formal arguments must be the same as the number of actual arguments at the invocation of this function subprogram.
A function can assign values to formal arguments. These values are returned to the calling program when the
RETURN
or
END
statements are executed in the function subprogram.
Restrictions
Alternate return specifiers are not allowed in
FUNCTION
statements.
f77
provides recursive calls. A function or subroutine is called recursively if it calls itself directly. If it calls another function or subroutine, which in turn calls this function or subroutine before returning, then it is also called recursively.
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Examples
Example 1: Character function:
CHARACTER*5 FUNCTION BOOL(ARG)
BOOL = 'TRUE'
IF (ARG .LE. 0) BOOL = 'FALSE'
RETURN
END
In the above example,
BOOL
is defined as a function of type
CHARACTER
with a length of 5 characters. This function when called returns the string,
TRUE
or
FALSE
, depending on the value of the variable,
ARG
.
Example 2: Real function:
FUNCTION SQR (A)
SQR = A*A
RETURN
END
In the above example, the function
SQR
is defined as function of type
REAL
by default, and returns the square of the number passed to it.
Example 3: Size of function, alternate syntax: ♦
INTEGER FUNCTION FCN*2 ( A, B, C )
The above nonstandard form is treated as:
INTEGER*2 FUNCTION FCN ( A, B, C )
4.36
GO TO
(Assigned)
The assigned
GO TO
statement branches to a statement label identified by the assigned label value of a variable.
Statements
157
158
4
Syntax
GO TO
i
[ [,] (
s
[,
s
] … ) ]
i s
Integer variable name
Statement label of an executable statement
Description
Execution proceeds as follows:
1. At the time an assigned
GO TO
statement is executed, the variable i must have been assigned the label value of an executable statement in the same program unit as the assigned
GO TO
statement.
2. If an assigned
GO TO
statement is executed, control transfers to a statement identified by i.
3. If a list of statement labels is present, the statement label assigned to i must be one of the labels in the list.
Restrictions
i must be assigned by an
ASSIGN
statement in the same program unit as the
GO TO
statement.
i must be
INTEGER*4
or
INTEGER*8
, not
INTEGER*2
.
s must be in the same program unit as the
GO TO
statement.
The same statement label can appear more than once in a
GO TO
statement.
The statement you jump to must be executable, not
DATA
,
ENTRY
,
FORMAT
, or
INCLUDE
.
You cannot jump into a
DO
,
IF
,
ELSE IF
, or
ELSE
block from outside the block.
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4
Example
Example: Assigned
GO TO
:
ASSIGN 10 TO N
…
GO TO N ( 10, 20, 30, 40 )
…
10 CONTINUE
…
40 STOP
4.37
GO TO
(Computed)
The computed
GO TO
statement selects one statement label from a list, depending on the value of an integer or real expression, and transfers control to the selected one.
Syntax
GO TO (
s
[,
s
] … ) [,]
e
s Statement label of an executable statement
e Expression of type integer or real
Description
Execution proceeds as follows:
1. e is evaluated first. It is converted to integer, if required.
2. If
1
≤
e
≤
n, where n is the number of statement labels specified, then the
e
th
label is selected from the specified list and control is transferred to it.
3. If the value of e is outside the range, that is, e <
1
or e > n, then the computed
GO TO
statement serves as a
CONTINUE
statement.
Statements
159
4
Restrictions
s must be in the same program unit as the
GO TO
statement.
The same statement label can appear more than once in a
GO TO
statement.
The statement you jump to must be executable, not
DATA
,
ENTRY
,
FORMAT
, or
INCLUDE
.
You cannot jump into a
DO
,
IF
,
ELSE IF
, or
ELSE
block from outside the block.
Example
Example: Computed
GO TO
:
…
GO TO ( 10, 20, 30, 40 ), N
…
10 CONTINUE
…
20 CONTINUE
…
40 CONTINUE
In the above example:
•
If
N=1
, then go to 10.
•
If
N=2
, then go to 20.
•
If
N=3
, then go to 30.
•
If
N=4
, then go to 40.
•
If
N
<1 or
N>4
, then fall through to 10.
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4.38
GO TO
(Unconditional)
The unconditional
GO TO
statement transfers control to a specified statement.
Syntax
GO TO
s s
Statement label of an executable statement
Description
Execution of the
GO TO
statement transfers control to the statement labeled s.
Restrictions
s must be in the same program unit as the
GO TO
statement.
The statement you jump to must be executable, not a
DATA
,
ENTRY
,
FORMAT
, or
INCLUDE
statement.
You cannot jump into a
DO
,
IF
,
ELSE IF
, or
ELSE
block from outside the block.
Example
A = 100.0
B = 0.01
GO TO 90
…
90 CONTINUE
Statements
161
4
4.39
IF
(Arithmetic)
The arithmetic
IF
statement branches to one of three specified statements, depending on the value of an arithmetic expression.
Syntax e
IF (
e
)
s1
,
s2
,
s3
Arithmetic expression: integer, real, double precision, or quadruple precision
s1, s2, s3
Labels of executable statements
Description
The
IF
statement transfers control to the first, second, or third label if the value of the arithmetic expression is less than zero, equal to zero, or greater than zero, respectively.
The restrictions are:
•
The s1, s2, s3 must be in the same program unit as the
IF
statement.
•
The same statement label can appear more than once in a
IF
statement.
•
The statement you jump to must be executable, not
DATA
,
ENTRY
,
FORMAT
, or
INCLUDE
.
•
You cannot jump into a
DO
,
IF
,
ELSE IF
, or
ELSE
block from outside the block.
Example
N = 0
IF ( N ) 10, 20, 30
Since the value of
N
is zero, control is transferred to statement label
20
.
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4.40
IF
(Block)
The block
IF
statement executes one of two or more sequences of statements, depending on the value of a logical expression.
Syntax
IF (
e
) THEN
…
END IF
e
A logical expression
Description
The block
IF
statement evaluates a logical expression and, if the logical expression is true, it executes a set of statements called the
IF
block. If the logical expression is false, control transfers to the next
ELSE
,
ELSE IF
, or
END
IF
statement at the same
IF
-level.
IF
Level
The
IF
level of a statement S is the value n1–n2, where n1 is the number of block
IF
statements from the beginning of the program unit up to the end, including S; n2 is the number of
END IF
statements in the program unit up to, but not including, S.
Example: In the following program, the
IF
-level of statement 9 is 2-1, or, 1:
IF ( X .LT. 0.0 ) THEN
MIN = NODE
END IF
…
9 IF ( Y .LT. 0.0 ) THEN
MIN = NODE - 1
END IF
Statements
163
164
4
The
IF
-level of every statement must be zero or positive. The
IF
-level of each block
IF
,
ELSE IF
,
ELSE
, and
END IF
statement must be positive. The
IF
-level of the
END
statement of each program unit must be zero.
IF
Block
An
IF
block consists of all the executable statements following the block
IF statement, up to, but not including, the next
ELSE
,
ELSE IF
, or
END IF statement that has the same if
level as the block
IF
statement. An
IF
block can be empty. In the following example, the two assignment statements form an
IF
block:
IF ( X .LT. Y ) THEN
M = 0
N = N+1
END IF
Execution proceeds as follows:
1. The logical expression e is evaluated first. If e is true, execution continues with the first statement of the
IF
block.
2. If e is true and the
IF
block is empty, control is transferred to the next
END
IF
statement with the same
IF
level as the block
IF
statement.
3. If e is false, control is transferred to the next
ELSE IF
,
ELSE
, or
END IF
statement with the same
IF
level as the block
IF
statement.
4. If the last statement of the
IF
block does not result in a branch to a label, control is transferred to the next
END IF
statement that has the same
IF
level as the block
IF
statement preceding the
IF
block.
Restrictions
You cannot jump into an
IF
block from outside the
IF
block.
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4
Examples
Example 1:
IF-THEN-ELSE
:
IF ( L ) THEN
N=N+1
ELSE
CALL CALC
K=K+1
CALL DISP
END IF
Example 2:
IF-THEN-ELSE-IF
with
ELSE-IF
:
IF ( C .EQ. 'a' ) THEN
NA=NA+1
CALL APPEND
ELSE IF ( C .EQ. 'b' ) THEN
NB=NB+1
CALL BEFORE
ELSE IF ( C .EQ. 'c' ) THEN
NC=NC+1
CALL CENTER
END IF
Example 3: Nested
IF-THEN-ELSE
:
IF ( PRESSURE .GT 1000.0 ) THEN
IF ( N .LT. 0.0 ) THEN
X = 0.0
ELSE
Y = 0.0
Z = 0.0
END IF
ELSE IF ( TEMPERATURE .GT. 547.0 ) THEN
Z = 1.0
ELSE
X = 1.0
Y = 1.0
END IF
Statements
165
4
4.41
IF
(Logical)
The logical
IF
statement executes one single statement, or does not execute it, depending on the value of a logical expression.
Syntax
IF (
e
)
st
e Logical expression st Executable statement
Description
The logical
IF
statement evaluates a logical expression and executes the specified statement if the value of the logical expression is true. The specified statement is not executed if the value of the logical expression is false, and execution continues as though a
CONTINUE
statement had been executed.
st can be any executable statement, except a
DO
block,
IF
,
ELSE IF
,
ELSE
,
END IF
,
END
, or another logical
IF
statement.
Example
IF ( VALUE .LE. ATAD ) CALL PUNT !
Note that there is no
THEN
.
IF ( TALLY .GE. 1000 ) RETURN
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4.42
IMPLICIT
The
IMPLICIT
statement confirms or changes the default type of names.
Syntax
IMPLICIT
type
(
a
[,
a
] … ) [,
type
(
a
[,
a
] … ) ] or:
IMPLICIT NONE or:
IMPLICIT UNDEFINED(A-Z)
◆
type is one of the following permitted types:
BYTE
◆
CHARACTER
CHARACTER*
n
CHARACTER*(*)
COMPLEX
COMPLEX*8
◆
COMPLEX*16
◆
COMPLEX*32
◆ (SPARC only)
DOUBLE COMPLEX
◆
DOUBLE PRECISION
INTEGER
INTEGER*2
INTEGER*4
INTEGER*8
LOGICAL
LOGICAL*1
LOGICAL*2
LOGICAL*4
LOGICAL*8
◆
◆
◆
◆
◆
◆
◆
REAL
REAL*4
REAL*8
◆
◆
REAL*16
◆ (SPARC only)
AUTOMATIC
◆
STATIC
◆
n must be greater than 0.
a is either a single letter or a range of single letters in alphabetical order. A range of letters can be specified by the first and last letters of the range, separated by a minus sign.
Description
The different uses for implicit typing and no implicit typing are described here.
Implicit Typing
The
IMPLICIT
statement can also indicate that no implicit typing rules apply in a program unit.
Statements
167
168
4
Restrictions
IMPLICIT
statements must precede all other specification statements.
The same letter can appear more than once as a single letter, or in a range of letters in all
IMPLICIT
statements of a program unit. ♦
The FORTRAN 77 Standard restricts this usage to only once. For f77
, if a letter is used twice, each usage is declared in order. See Example 4.
Examples
An
IMPLICIT
statement specifies a type and size for all user-defined names that begin with any letter, either a single letter or in a range of letters, appearing in the specification.
An
IMPLICIT
statement does not change the type of the intrinsic functions.
An
IMPLICIT
statement applies only to the program unit that contains it.
A program unit can contain more than one
IMPLICIT
statement.
IMPLICIT
types for particular user names are overridden by a type statement.
No Implicit Typing
The second form of
IMPLICIT
specifies that no implicit typing should be done for user-defined names, and all user-defined names shall have their types declared explicitly.
If either
IMPLICIT NONE
or
IMPLICIT UNDEFINED (A-Z)
is specified, there cannot be any other
IMPLICIT
statement in the program unit.
Example 1:
IMPLICIT
: everything is integer:
IMPLICIT INTEGER (A-Z)
X = 3
K = 1
STRING = 0
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4
Example 2: Complex if it starts with
U
,
V
, or
W
; character if it starts with
C
or
S
:
IMPLICIT COMPLEX (U,V,W), CHARACTER*4 (C,S)
U1 = ( 1.0, 3.0)
STRING = 'abcd'
I = 0
X = 0.0
Example 3: All items must be declared:
IMPLICIT NONE
CHARACTER STR*8
INTEGER N
REAL Y
N = 100
Y = 1.0E5
STR = 'Length'
In the above example, once
IMPLICIT NONE
is specified in the beginning. All the variables must be declared explicitly.
Example 4: A letter used twice: ♦
IMPLICIT INTEGER (A-Z)
IMPLICIT REAL (A-C)
C = 1.5E8
D = 9
In the above example,
D
through
Z
implies
INTEGER
, and
A
through
C
implies
REAL
.
Statements
169
4
4.43
INCLUDE
The
INCLUDE
♦ statement inserts a file into the source program.
Syntax
INCLUDE '
file
' or:
INCLUDE
"file
"
file
Name of the file to be inserted
Description
The contents of the named file replace the
INCLUDE
statement.
Search Path
If the name referred to by the
INCLUDE
statement begins with the character
/
, then it is taken by f77
to mean the absolute path name of the
INCLUDE
file.
Otherwise, f77
looks for the file in the following directories, in this order:
1. The directory that contains the source file with the
INCLUDE
statement
2. The directories that are named in the
-I
loc options
3. The current directory in which the f77
command was issued
4. The directories in the default list. This is different in Solaris 1.x and 2.x.
The default list varies between Solaris 1.x and 2.x.
For Solaris 2.x, if you installed into the standard directory, the default list is:
/opt/SUNWspro/SC4.0/include/f77 /usr/include
If you installed into nonstandard directory
/
mydir
/
, then it is:
/
mydir
/SUNWspro/SC4.0/include/f77 /usr/include
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For Solaris 1.x, if you installed in the standard directory, then the default list is:
/usr/lang/SC4.0/include/f77 /usr/include
If you installed into nonstandard directory
/
mydir
/
, then it is:
/
mydir
/SC4.0/include/f77 /usr/include
The release number,
SC4.0
, varies with the release of the set of compilers.
These
INCLUDE
statements can be nested ten deep.
Preprocessor
#include
The paths and order searched for the
INCLUDE
statement are not the same as those searched for the preprocessor
#include
directive, described under
-I
in the FORTRAN 77 4.0 User’s Guide. Files included by the preprocessor
#include
directive can contain
#defines
and the like; files included with the compiler
INCLUDE
statement must contain only FORTRAN 77 statements.
VMS Logical File Names in the
INCLUDE
Statement
f77
interprets VMS logical file names on the
INCLUDE
statement if:
•
The
-xl[d]
compiler option is set.
•
The environment variable
LOGICALNAMEMAPPING
is there to define the mapping between the logical names and the UNIX path name.
f77
uses the following rules for the interpretation:
•
The environment variable should be set to a string with the syntax:
"
lname1=path1; lname2=path2; …
" where each lname is a logical name and each path1, path2, and so forth is the path name of a directory (without a trailing
/
).
•
All blanks are ignored when parsing this string. It strips any trailing
/[no]
list from the file name in the
INCLUDE
statement.
•
Logical names in a file name are delimited by the first : in the VMS file name, so f77
converts file names of the lname1
:
file form to the path1
/
file
form.
Statements
171
172
4
•
For logical names, uppercase and lowercase are significant. If a logical name is encountered on the
INCLUDE
statement which is not specified in the
LOGICALNAMEMAPPING
, the file name is used, unchanged.
Examples
Example 1:
INCLUDE
, simple case:
INCLUDE 'stuff'
The above line is replaced by the contents of the file stuff
.
Example 2:
INCLUDE
, search paths:
For the following conditions:
•
Your source file has the line:
INCLUDE 'ver1/const.h'
•
Your current working directory is
/usr/ftn
.
•
Your source file is
/usr/ftn/projA/myprg.f
.
In this example, f77
seeks const.h
in these directories, in the order shown.
For Solaris 2.x, If you installed into the standard directory, then f77
searches these directories:
•
/usr/ftn/projA/ver1
•
/usr/ftn/ver1
•
/opt/SUNWspro/SC4.0/include/f77/ver1
•
/usr/include
If you installed into nonstandard directory /mydir, it searches these directories:
•
/usr/ftn/projA/ver1
•
/usr/ftn/ver1
•
/mydir
/SUNWspro/SC4.0/include/f77/ver1
•
usr/include
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4
For Solaris 1.x, if you installed into the standard directory, then f77
searches these directories:
•
/usr/ftn/projA/ver1
•
/usr/ftn/ver1
•
/usr/lang/SC4.0/include/f77/ver1
•
/usr/include
If you installed into nonstandard directory /mydir/, it searches these directories:
•
/usr/ftn/projA/ver1
•
/usr/ftn/ver1
•
/
mydir
/SC4.0/include/f77/ver1
•
/usr/include
4.44
INQUIRE
Syntax
The
INQUIRE
statement returns information about a unit or file.
An inquire by unit has the general form:
INQUIRE( [ UNIT=]
u
,
slist
)
An inquire by file has the general form:
INQUIRE( FILE=
fn
,
slist
)
fn
Name of the file being queried
u slist
Unit of the file being queried
Specifier list
The
INQUIRE
slist can include one or more of the following, in any order:
•
ERR
= s
•
EXIST
= ex
•
OPENED
= od
•
NAMED
= nmd
•
ACCESS
= acc
Statements
173
4
174
•
SEQUENTIAL
= seq
•
DIRECT
= dir
•
FORM
= fm
•
FORMATTED
= fmt
•
UNFORMATTED
= unf
•
NAME
= fn
•
BLANK
= blnk
•
IOSTAT
= ios
•
NUMBER
= num
•
RECL
= rcl
•
NEXTREC
= nr
Description
You can determine such things about a file as whether it exists, is opened, or is connected for sequential I/O. That is, files have such attributes as name, existence (or nonexistence), and the ability to be connected in certain ways
(
FORMATTED
,
UNFORMATTED
,
SEQUENTIAL
, or
DIRECT
).
You can inquire either by unit or by file, but not by both in the same
INQUIRE statement.
In this system environment, the only way to discover what permissions you have for a file is to use the
ACCESS
(3F) function. The
INQUIRE
statement does not determine permissions.
The specifiers for
INQUIRE
are:
•
FILE =
fn—n is a character expression or * with the name of the file.
Trailing blanks in the file name are ignored. If the file name is all blanks, that means the current directory. The file need not be connected to a unit in the current program.
•
UNIT =
u—u is an integer expression or * with the value of the unit.
Exactly one of
FILE
or
UNIT
must be used.
•
IOSTAT =
ios—ios is as in the
OPEN
statement.
•
ERR =
s—s is a statement label of a statement to branch to if an error occurs during the execution of the
INQUIRE
statement.
•
EXIST =
ex—ex is a logical variable that is set to
.TRUE.
if the file or unit exists, and
.FALSE.
otherwise.
FORTRAN 77 Reference Manual
4
•
OPENED =
od—od is a logical variable that is set to
.TRUE.
if the file is connected to a unit or the unit is connected to a file, and
.FALSE.
otherwise.
•
NUMBER =
num—num is an integer variable that is assigned the number of the unit connected to the file, if any. If no file is connected, the variable is unchanged.
•
NAMED =
nmd—nmd is a logical variable that is assigned
.TRUE.
if the file has a name,
.FALSE.
otherwise.
•
NAME =
fn—fn is a character variable that is assigned the name of the file connected to the unit. If you do an inquire-by-unit, the name parameter is undefined, unless both the values of the
OPENED
and
NAMED
variables are both true. If you do an inquire by file, the name parameter is returned, even though the FORTRAN 77 Standard leaves it undefined.
•
ACCESS =
acc—acc is a character variable that is assigned the value
'SEQUENTIAL'
if the connection is for sequential I/O and
'DIRECT'
if the connection is for direct I/O. The value is undefined if there is no connection.
•
SEQUENTIAL =
seq—seq is a character variable that is assigned the value
'YES'
if the file could be connected for sequential I/O,
'NO'
if the file could not be connected for sequential I/O, and
'UNKNOWN'
if the system can’t tell.
•
DIRECT =
dir—dir is a character variable that is assigned the value
'YES' if the file could be connected for direct I/O,
'NO'
if the file could not be connected for direct I/O, and
'UNKNOWN'
if the system can’t tell.
•
FORM =
fm—fm is a character variable which is assigned the value
'FORMATTED'
if the file is connected for formatted I/O and
'UNFORMATTED'
if the file is connected for unformatted I/O.
•
FORMATTED =
fmt—fmt is a character variable that is assigned the value
'YES'
if the file could be connected for formatted I/O,
'NO'
if the file could not be connected for formatted I/O, and
'UNKNOWN'
if the system cannot tell.
•
UNFORMATTED =
unf—unf is a character variable that is assigned the value
'YES'
if the file could be connected for unformatted I/O,
'NO'
if the file could not be connected for unformatted I/O, and
'UNKNOWN'
if the system cannot tell.
Statements
175
4
•
RECL =
rcl—rcl is an integer variable that is assigned the record length of the records in the file if the file is connected for direct access.
f77
does not adjust the rcl returned by
INQUIRE
. The
OPEN
statement does such an adjustment if the
-xl[d]
option is set. For an explanation of
-xl[d]
, see the section, “Details of Features That Require -xl[d]” on page 437.
•
NEXTREC =
nr— nr is an integer variable that is assigned one more than the number of the last record read from a file connected for direct access.
•
BLANK =
blnk—blnk is a character variable that is assigned the value
'NULL'
if null blank control is in effect for the file connected for formatted
I/O, and
'ZERO'
if blanks are being converted to zeros and the file is connected for formatted I/O.
Example: An
OPEN
statement in which declarations are omitted:
OPEN( 1, FILE='/dev/console' )
For f77,
this statement opens the console for formatted sequential I/O. An
INQUIRE
for either unit 1 or the file,
/dev/console
, reveals that the file:
•
Exists
•
Is connected to unit 1
•
Has the name
/dev/console
•
Is opened for sequential I/O
•
Could be connected for sequential I/O
•
Cannot be connected for direct I/O, that is cannot seek
•
Is connected for formatted I/O
•
Can be connected for formatted I/O
•
Cannot be connected for unformatted I/O, that is, cannot seek
•
Has neither a record length nor a next record number
•
Is ignoring blanks in numeric fields
176
FORTRAN 77 Reference Manual
The following table summarizes the
INQUIRE
options:
The asterisk (
*
) indicates the returned value is undefined for inquire-by-unit in the
FORTRAN 77 Standard, but is defined in f77
.
The returned value is undefined for inquire-byfile in the FORTRAN 77
Standard, but is defined in
† f77
indicates the
.
BLANK
DIRECT *
ERR
EXIST
FORM
Table 4-2
INQUIRE
Options Summary
SPECIFIER
ACCESS
FORMATTED *
IOSTAT
NAME †
NAMED †
NEXTREC
NUMBER *
OPENED
RECL
SEQUENTIAL *
UNFORMATTED *
Form: SPECIFIER = Variable
Value of Variable Data Type of Variable
'DIRECT'
'SEQUENTIAL'
CHARACTER
CHARACTER
CHARACTER
'NULL','ZERO'
'YES'
'NO'
'UNKNOWN'
Statement number
.TRUE., .FALSE.
INTEGER
LOGICAL
CHARACTER 'FORMATTED'
'UNFORMATTED'
'YES'
'NO'
'UNKNOWN'
Error number
Name of the file
.TRUE., .FALSE.
Next record number
Unit number
.TRUE., .FALSE.
Record length
'YES'
'NO'
'UNKNOWN'
'YES'
'NO'
'UNKNOWN'
CHARACTER
INTEGER
CHARACTER
LOGICAL
INTEGER
INTEGER
LOGICAL
INTEGER
CHARACTER
CHARACTER
4
Statements
177
178
4
Also:
•
If a file is scratch, then
NAMED
and
NUMBER
are not returned.
•
If there is no file with the specified name, then these variables are not returned:
DIRECT
,
FORMATTED
,
NAME
,
NAMED
,
SEQUENTIAL
, and
UNFORMATTED
.
•
If
OPENED=.FALSE.
, then these variables are not returned:
ACCESS
,
BLANK
,
FORM
,
NEXTREC
, and
RECL
.
•
If no file is connected to the specified unit, then these variables are not returned:
ACCESS
,
BLANK
,
DIRECT
,
FORM
,
FORMATTED
,
NAME
,
NAMED
,
NEXTREC
,
NUMBER
,
RECL
,
SEQUENTIAL
, and
UNFORMATTED
.
•
If
ACCESS='SEQUENTIAL'
, then these variables are not returned:
RECL
and
NEXTREC
.
•
If
FORM='UNFORMATTED’
, then
BLANK
is not returned.
Examples
Example 1: Inquire by unit:
LOGICAL OK
INQUIRE( UNIT=3, OPENED=OK )
IF ( OK ) CALL GETSTD ( 3, STDS )
Example 2: Inquire by unit—omit the
UNIT=
:
LOGICAL OK
INQUIRE( 3, OPENED=OK )
IF ( OK ) CALL GETSTD ( 3, STDS )
Example 3: Inquire by file:
LOGICAL THERE
INQUIRE( FILE='.profile', EXIST=THERE )
IF ( THERE ) CALL GETPROFILE( FC, PROFILE )
FORTRAN 77 Reference Manual
4
Example 4: More than one answer:
CHARACTER FN*32
LOGICAL HASNAME, OK
INQUIRE ( UNIT=3, OPENED=OK, NAMED=HASNAME, NAME=FN )
IF ( OK .AND. HASNAME ) PRINT *, 'Filename="', FN, '"'
4.45
INTEGER
The
INTEGER
statement specifies the type to be integer for a symbolic constant, variable, array, function, or dummy function.
Optionally, it specifies array dimensions and size and initializes with values.
Syntax
INTEGER [*
len
[,]]
v
[*
len
[/
c
/]] [,
v
[*
len
[/
c
/]] …
v
Name of a symbolic constant, variable, array, array declarator, function, or dummy function
len
Either 2, 4, or 8, the length in bytes of the symbolic constant, variable, array element, or function. 8 is allowed only if
-dbl
is on. ♦
c
List of constants for the immediately preceding name
Description
If you specify the size as 2, 4, or 8, you get what you specify; if you do not specify the size, you get the default size.
Default Size
The default size depends on
–i2
and
–r8
.
•
If the
–i2
option is on the f77
command line, then the default length is 2; otherwise, the default is 4.
Statements
179
180
4
•
If the
–r8
option is on the f77
command line, then the compiler allocates 8 bytes, but still performs only 4-byte arithmetic. This is done to satisfy the requirements of the FORTRAN 77 Standard that an integer and a real datum are allocated the same amount of storage.
•
If the
-dbl
option is on, then the compiler allocates 8 bytes and performs 8byte arithmetic as well.
•
If you put both
–i2
and
–r8
on the f77
command line, the results are unpredictable.
Restrictions
Do not use
INTEGER*8
variables or 8-byte constants or expressions when indexing arrays, otherwise, only 4 low-order bytes are taken into account. This action can cause unpredictable results in your program if the index value exceeds the range for 4-byte integers.
We recommend that you not use
INTEGER*8
in your code, since the program will not compile if you omit
-dbl
. Instead, use
INTEGER
and compile with
-dbl
, which automatically converts
INTEGER
to 64-bit integers.
Examples
Example 1: Each of these integer scalars is equivalent to the others, if there is no
–i2
:
INTEGER U, V
INTEGER*4 U, V
INTEGER U*4, V*4
Do not use all three lines in the same program unit—you cannot declare anything more than once in the same program unit.
Example 2: Initialize:
INTEGER U / 1 /, V / 4 /, W*2 / 1 /, X*2 / 4 /
FORTRAN 77 Reference Manual
4
Example 3: Use any one of these lines for integer arrays; they are equivalent:
INTEGER U(9), V(9)
INTEGER*4 U(9), V(9)
INTEGER U*4(9), V(9)*4
4.46
INTRINSIC
The
INTRINSIC
statement lists intrinsic functions that can be passed as actual arguments.
Syntax
INTRINSIC
fun
[,
fun
] …
fun
Function name
Description
If the name of an intrinsic function is used as an actual argument, it must appear in an
INTRINSIC
statement in the same program unit.
Example: Intrinsic functions passed as actual arguments:
INTRINSIC SIN, COS
X = CALC ( SIN, COS )
Restrictions
A symbolic name must not appear in both an
EXTERNAL
and an
INTRINSIC statement in the same program unit.
The actual argument must be a specific name. Most generic names are also specific, but a few are not:
IMAG
,
LOG
, and
LOG10
.
A symbolic name can appear more than once in an
INTRINSIC
statement. ♦ In the FORTRAN 77 Standard, a symbolic name can appear only once in an
INTRINSIC
statement.
Statements
181
4
Because they are in-line or generic, the following intrinsics cannot be passed as
actual arguments:
Table 4-3
Intrinsics That Cannot Be Passed As Actual Arguments
LOC
AND
IAND
IIAND
JIAND
OR
IOR
IIOR
IEOR
IIEOR
JIOR
JIEOR
NOT
INOT
JNOT
XOR
LSHIFT
RSHIFT
INT
IINT
JINT
IQINT
IIQINT
JIQINT
IFIX
IIFIX
JIFIX
IDINT
IIDINT
JIDINT
FLOAT
FLOATI
FLOATJ
DFLOAT
DFLOTI
DFLOTJ
SNGL
SNGLQ
REAL
DREAL
DBLE
DBLEQ
QEXT
QEXTD
QFLOAT
CMPLX
DCMPLX
ICHAR
IACHAR
ACHAR
CHAR
MAX
MAX0
AMAX0
AIMAX0
AJMAX0
IMAX0
JMAX0
MAX1
AMAX1
DMAX1
IMAX1
JMAX1
QMAX1
MIN
MIN0
AMIN0
AIMIN0
AJMIN0
IMIN0
JMIN0
MIN1
AMIN1
DMIN1
IMIN1
JMIN1
QMIN1
IMAG
EPBASE
EPEMAX
EPEMIN
EPHUGE
EPMRSP
EPPREC
EPTINY
LOG
LOG10
QREAL
QCMPLX
SIZEOF
4.47
LOGICAL
The
LOGICAL
statement specifies the type to be logical for a symbolic constant, variable, array, function, or dummy function.
Optionally, it specifies array dimensions and initializes with values.
182
FORTRAN 77 Reference Manual
4
Syntax c
LOGICAL [*
len
[,]]
v
[*
len
[/
c
/]] [,
v
[*
len
[/
c
/]] …
v len
Name of a symbolic constant, variable, array, array declarator, function, or dummy function
Either 1, 2, 4, or 8, the length in bytes of the symbolic constant, variable, array element, or function. 8 is allowed only if
-dbl
is on.
♦
List of constants for the immediately preceding name
Description
Default Size
The default size depends on
–i2
and
–r8
:
•
If the
–i2
option is on the f77
command line, then the default length is 2; otherwise, the default is 4.
•
If the
–r8
or
-dbl
option is on the f77
command line, then the compiler allocates 8 bytes. If
-dbl
is specified, 8-byte arithmetic is done, otherwise only 4-byte arithmetic is performed. This is to satisfy the requirements of the
FORTRAN 77 Standard that an integer and a real datum are allocated the same amount of storage.
•
If you put both
–i2
and
–r8
on the f77
command line, the results are unpredictable.
Examples
If you specify the size as 1, 2, or 4, then you get what you specify; but if you do
not specify the size, you get the default size.
Example 1: Each of these statements is equivalent to the others, if there is no
-i2
:
LOGICAL U, V
LOGICAL*4 U, V
LOGICAL U*4, V*4
Statements
183
4
Do not use all three statements in the same program unit—you cannot declare anything more than once in the same program unit.
Example 2: Initialize:
LOGICAL U /.false./, V /0/, W*4 /.true./, X*4 /'z'/
4.48
MAP
The
MAP
♦ declaration defines alternate groups of fields in a union.
Syntax
MAP
field-declaration
…
[
field-declaration
]
END MAP
Description
Each field declaration can be one of the following:
•
Type declaration, which can include initial values
•
Substructure—either another structure declaration, or a record that has been previously defined
•
Union declaration—see Section 4.70, “UNION and MAP
,
” for more details
184
FORTRAN 77 Reference Manual
Example
Example:
MAP
:
STRUCTURE /STUDENT/
CHARACTER*32 NAME
INTEGER*2 CLASS
UNION
MAP
CHARACTER*16 MAJOR
END MAP
MAP
INTEGER*2 CREDITS
CHARACTER*8 GRAD_DATE
END MAP
END UNION
END STRUCTURE
4.49
NAMELIST
The
NAMELIST
♦ statement defines a list of variables or array names, and associates it with a unique group name.
Syntax
NAMELIST /
grname
/
namelist
[[,] /
grname
/
namelist
] …
grname
Symbolic name of the group
namelist
List of variables and arrays
Description
The
NAMELIST
statement contains a group name and other items.
4
Statements
185
186
4
Group Name
The group name is used in the namelist-directed I/O statement to identify the list of variables or arrays that are to be read or written. This name is used by namelist-directed I/O statements instead of an input/output list. The group name must be unique, and identifies a list whose items can be read or written.
A group of variables can be defined through several
NAMELIST
statements with the same group name. Together, these definitions are taken as defining one
NAMELIST
group.
Namelist Items
The namelist items can be of any data type. The items in the namelist can be variables or arrays, and can appear in more than one namelist. Only the items specified in the namelist can be read or written in namelist-directed I/O, but it is not necessary to specify data in the input record for every item of the namelist.
The order of the items in the namelist controls the order in which the values are written in namelist-directed output. The items in the input record can be in any order.
Restrictions
Input data can assign values to the elements of arrays or to substrings of strings that appear in a namelist.
The following constructs cannot appear in a
NAMELIST
statement:
•
Constants (parameters)
•
Array elements
•
Records and record fields
•
Character substrings
•
Dummy assumed-size arrays
See Chapter 5, “Input and Output,” for more details on namelist.
FORTRAN 77 Reference Manual
4
Example
Example: The
NAMELIST
statement:
CHARACTER*16 SAMPLE
LOGICAL*4 NEW
REAL*4 DELTA
NAMELIST /CASE/ SAMPLE, NEW, DELTA
In this example, the group
CASE
has three variables:
SAMPLE
,
NEW
, and
DELTA
.
4.50
OPEN
The
OPEN
statement connects an existing external file to a unit, or creates a file and connects it to a unit, or changes some specifiers of the connection.
Syntax
OPEN(
KEYWORD1
=
value1, KEYWORD2
=
value2
, … )
KEYWORDn
A valid keyword specifier, as listed below
Description
For tape, it is more reliable to use the
TOPEN()
routines. The
OPEN
statement determines the type of file named, whether the connection specified is legal for the file type (for instance,
DIRECT
access is illegal for tape and tty
devices), and allocates buffers for the connection if the file is on tape or if the subparameter
FILEOPT
='
BUFFER
=n' is specified. Existing files are never truncated on opening. The options can be specified in any order.
Table 4-4
OPEN
Keyword Specifier Summary
Alternate Form Standard Form
[UNIT=]
u
FILE =
fin
ACCESS =
acc
NAME =
fin
Statements
187
188
4
Table 4-4
OPEN
Keyword Specifier Summary (Continued)
Alternate Form Standard Form
BLANK =
blnk
ERR =
s
FORM =
fm
IOSTAT =
ios
RECL =
rl
STATUS =
sta
FILEOPT =
fopt
READONLY
♦
♦
ACTION =
act
♦
RECORDSIZE =
rl
TYPE =
sta
Details of the
OPEN
keyword specifier are listed in the following table.
Table 4-5
OPEN
Keyword Specifier Details
[
UNIT=
] u
u is an integer expression or an asterisk (*) that specifies the unit number. u is required. If u is first in the parameter list, then
UNIT=
can be omitted.
FILE=
fin
fin is a character expression or * naming the file to open. An
OPEN
statement need not specify a file name. If the file name is not specified, a default name is created.
Reopen—If you open a unit that is already open without specifying a file name (or with the previous file name),
FORTRAN 77 thinks you are reopening the file to change parameters. The file position is not changed. The only parameters you are allowed to change are
BLANK
(
NULL
or
ZERO
) and
FORM
(
FORMATTED
or
). To change any other parameters, you must close, then reopen the file.
Switch Files—If you open a unit that is already open, but you specify a different file name, it is as if you closed with the old file name before the open.
Switch Units—If you open a file that is already open, but you specify a different unit, that is an error. This error is
not detected by the
ERR=
option, however, and the program does not terminate abnormally.
Scratch—If a file is opened with
STATUS
='
SCRATCH
', a temporary file is created and opened. See
STATUS
=sta.
FORTRAN 77 Reference Manual
4
Table 4-5
OPEN
Keyword Specifier Details (Continued)
ACCESS=
acc
The
ACCESS=
acc clause is optional. acc is a character expression. Possible values are:
APPEND
,
DIRECT
, or
SEQUENTIAL
. The default is
SEQUENTIAL
.
If
ACCESS='APPEND
':
SEQUENTIAL
and
FILEOPT='EOF
' are assumed. This is for opening a file to append records to an existing sequential-access file. Only
WRITE
operations are allowed. This is an extension.
♦
If
ACCESS='DIRECT
':
RECL
must also be given, since all I/O transfers are done in multiples of fixed-size records.
Only directly accessible files are allowed; thus, tty, pipes, and magnetic tape are not allowed. If you build a file as sequential, then you cannot access it as direct.
If
FORM
is not specified, unformatted transfer is assumed.
If
FORM
='
UNFORMATTED
', the size of each transfer depends upon the data transferred.
If
ACCESS='SEQUENTIAL
',
RECL
is ignored.
♦
The FORTRAN 77 Standard prohibits
RECL
for sequential access.
No padding of records is done.
If you build a file as direct, then you cannot access it as sequential.
Files do not have to be randomly accessible, in the sense that tty, pipes, and tapes can be used. For tapes, we recommend the
TOPEN()
routines because they are more reliable.
If
FORM
is not specified, formatted transfer is assumed.
If
FORM
='
FORMATTED
', each record is terminated with a newline (
\n
) character; that is, each record actually has one extra character.
If
FORM
='
', the file acts like a
FORM
='
FORMATTED
' file, except for interpretation of the column-1 characters on the output (blank = single space, 0 = double space, 1 = form feed, and + = no advance).
If
FORM
='
UNFORMATTED
', each record is preceded and terminated with an
INTEGER*4
count, making each record
8 characters longer than normal. This convention is not shared with other languages, so it is useful only for communicating between FORTRAN 77 programs.
FORM=
fm
The
FORM=
fm clause is optional. fm is a character expression. Possible values are '
FORMATTED
', '
UNFORMATTED
', or
'
'.
♦
The default is '
FORMATTED
'.
This option interacts with
ACCESS
.
'
' makes it a print file. See Chapter 5, “Input and Output,” for details.
Statements
189
190
4
Table 4-5
OPEN
Keyword Specifier Details (Continued)
RECL=
rl
The
RECL=
rl clause is required if
ACCESS='DIRECT'
and ignored otherwise.
rl is an integer expression for the length in characters of each record of a file. rl must be positive.
If the record length is unknown, you can use
RECL=1
; see “Direct Access I/O” on page 261.
If
-xl[d]
is not set, rl is number of characters, and record length is rl.
If
-xl[d]
is set, rl is number of words, and record length is rl*4.
♦
There are more details in the
ACCESS
='
SEQUENTIAL
' section, above.
Each
WRITE
defines one record and each
READ
reads one record (unread characters are flushed).
The default buffer size for tape is 64K characters. For tapes, we recommend the
TOPEN()
routines because they are more reliable.
ERR=
s
The
ERR
=s clause is optional. s is a statement label of a statement to branch to if an error occurs during execution of the
OPEN
statement.
IOSTAT=
ios
The
IOSTAT
=ios clause is optional. ios is an integer variable that receives the error status from an
OPEN
. After the execution of the
OPEN
, if no error condition exists, then ios is zero; otherwise, it is some positive number.
If you want to avoid aborting the program when an error occurs on an
OPEN
, include
ERR
=s or
IOSTAT
=ios.
BLANK=
blnk
The
BLANK
=blnk clause is optional, and is for formatted input only. The blnk is a character expression that indicates how blanks are treated. Possible values are '
ZERO
' and '
NULL
'.
'
ZERO
'—Blanks are treated as zeroes.
'
NULL
'—Blanks are ignored during numeric conversion. This is the default.
STATUS=
sta
The
STATUS
=sta clause is optional. sta is a character expression. Possible values are:
'OLD'
,
'NEW'
,
'UNKNOWN'
, or
'SCRATCH'
.
'OLD'
— The file already exists (nonexistence is an error). For example:
STATUS='OLD'
.
'
NEW
' — The file doesn't exist (existence is an error). If
'FILE=
name
'
is not specified, then a file named ' fort.
n' is opened, where n is the specified logical unit.
'
UNKNOWN
' — Existence is unknown. This is the default.
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4
Table 4-5
OPEN
Keyword Specifier Details (Continued)
STATUS=
sta (Continued)
'
SCRATCH
' — For a file opened with
STATUS='SCRATCH'
, a temporary file with a name of the form tmp.F
AAAxnnnnn is opened. Any other
STATUS
specifier without an associated file name results in opening a file named ' fort.
n', where n is the specified logical unit number. By default, a scratch file is deleted when closed or during normal termination. If the program aborts, then the file may not be deleted. To prevent deletion,
CLOSE with
STATUS
='
KEEP
'.
The FORTRAN 77 Standard prohibits opening a named file as scratch: if
OPEN
has a
FILE
=name option, then it cannot have a
STATUS
='
SCRATCH
' option. This FORTRAN 77 extends the standard by allowing opening named files as scratch.
♦
Such files are normally deleted when closed or at normal termination.
TMPDIR
: FORTRAN 77 programs normally put scratch files in the current working directory. If the
TMPDIR environment variable is set to a writable directory, then the program puts scratch files there.
♦
FILEOPT=
fopt
♦
The
FILEOPT
=fopt clause is optional. fopt is a character expression. Possible values are '
NOPAD'
, '
BUFFER
=n', and
'
EOF
'.
'
NOPAD'
—Do not extend records with blanks if you read past the end-of-record (formatted input only). That is, a
short record causes an abort with an error message, rather than just filling with trailing blanks and continuing.
'
BUFFER
=n'— This suboption is for disks. For tapes, we recommend the
TOPEN()
routines because they are more reliable. It sets the size in bytes of the I/O buffer to use. For writes, larger buffers yield faster I/O. For good performance, make the buffer a multiple of the largest record size. This size can be larger than the actual physical memory, and probably the best performance is obtained by making the record size equal to the entire file size.
Larger buffer sizes can cause extra paging.
'
EOF
'—Opens a file at end-of-file rather than at the beginning (useful for appending data to file), for example,
FILEOPT='EOF'
. Unlike
ACCESS='APPEND
', in this case, both
READ
and
BACKSPACE
are allowed.
READONLY
♦
The file is opened read-only.
ACTION =
act
This specifier denotes file permissions. Possible values are:
READ
,
WRITE
, and
READWRITE
.
If act is
READ
, it specifies that the file is opened read-only.
If act is
WRITE
, it specifies that the file is opened write-only. You cannot execute a
BACKSPACE
statement on a write-only file.
If act is
READWRITE
, it specifies that the file is opened with both read and write permissions.
Statements
191
4
192
Examples
Here are six examples.
Example 1: Open a file and connect it to unit 8—either of the following forms of the
OPEN
statement opens the file, projectA/data.test
, and connects it to FORTRAN 77 unit 8:
OPEN( UNIT=8, FILE='projectA/data.test' )
OPEN( 8, FILE=’projectA/data.test’ )
In the above example, these properties are established by default: sequential access, formatted file, and (unwisely) no allowance for error during file open.
Example 2: Explicitly specify properties:
&
OPEN( UNIT=8, FILE='projectA/data.test',
ACCESS='SEQUENTIAL', FORM='FORMATTED' )
Example 3: Either of these opens file, fort.8
, and connects it to unit 8:
OPEN( UNIT=8 )
OPEN( 8 )
In the above example, you get sequential access, formatted file, and no allowance for error during file open. If the file, fort.8
does not exist before execution, it is created. The file remains after termination.
Example 4: Allowing for open errors:
OPEN( UNIT=8, FILE='projectA/data.test', ERR=99 )
The above statement branches to
99
if an error occurs during
OPEN
.
Example 5: Allowing for variable-length records;
OPEN( 1, ACCESS='DIRECT', recl=1 )
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4
For more information on variable-length records, see “Direct Access I/O” on page 261.
Example 6: Scratch file:
OPEN( 1, STATUS='SCRATCH' )
This statement opens a temporary file with a name, such as tmp.FAAAa003zU
.
The file is usually in the current working directory, or in
TMPDIR
if that environment variable is set.
4.51
OPTIONS
The
OPTIONS
♦ statement overrides compiler command-line options.
Syntax
OPTIONS /
qualifier
[/
qualifier
…]
Description
The following table shows the
OPTIONS
statement qualifiers:
Table 4-6
OPTIONS
Statement Qualifiers
Qualifier
/[NO]G_FLOATING
/[NO]I4
/[NO]F77
/CHECK=ALL
/CHECK=[NO]OVERFLOW
/CHECK=[NO]BOUNDS
/CHECK=[NO]UNDERFLOW
Action Taken
None (not implemented)
Enables/Disables the
-i2
option
None (not implemented)
Enables the
-C
option
None (not implemented)
Disables/Enables the
-C
option
None (not implemented)
Statements
193
194
4
Table 4-6
OPTIONS
Statement Qualifiers (Continued)
Qualifier
/CHECK=NONE
/NOCHECK
/[NO]EXTEND_SOURCE
Action Taken
Disables the
-C
option
Disables the
-C
option
Disables/enables the
-e
option
Restrictions
The
OPTIONS
statement must be the first statement in a program unit; it must be before the
BLOCK DATA
,
FUNCTION
,
PROGRAM
, and
SUBROUTINE statements.
Options set by the
OPTIONS
statement override those of the command line.
Options set by the
OPTIONS
statement endure for that program unit only.
A qualifier can be abbreviated to four or more characters.
Uppercase or lowercase is not significant.
Example
For the following source, integer variables declared with no explicit size occupy 4 bytes rather than 2, with or without the
–i2
option on the command line. This rule does not change the size of integer constants, only variables.
OPTIONS /I4
PROGRAM FFT
…
END
By way of contrast, if you use
/NOI4
, then all integer variables declared with no explicit size occupy 2 bytes rather than 4, with or without the
–i2
option on the command line. However, integer constants occupy 2 bytes with
–i2
, and 4 bytes otherwise.
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4
4.52
PARAMETER
The
PARAMETER
statement assigns a symbolic name to a constant.
Syntax
PARAMETER ( p=
e
[, p=e ] … )
p e
Symbolic name
Constant expression
An alternate syntax is allowed, if the
–xl
flag is set: ♦
PARAMETER
p
=
e
[,
p
=
e
] …
In this alternate form, the type of the constant expression determines the type of the name; no conversion is done.
Description
e
can be of any type and the type of symbolic name and the corresponding expression must match.
A symbolic name can be used to represent the real part, imaginary part, or both parts of a complex constant.
A constant expression is made up of explicit constants and parameters and the
FORTRAN 77 operators. See Section 3.6, “Constant Expressions,” for more details.
No structured records or record fields are allowed in a constant expression.
Exponentiation to a floating-point power is not allowed, and a warning is issued.
If the type of the data expression does not match the type of the symbolic name, then the type of the name must be specified by a type statement or
IMPLICIT
statement prior to its first appearance in a
PARAMETER
statement, otherwise conversion will be performed.
Statements
195
196
4
Restrictions
A symbolic constant must not be defined more than once in a program unit.
If a symbolic name appears in a
PARAMETER
statement, then it cannot represent anything else in that program unit.
A symbolic name cannot be used in a constant format specification, but it can be used in a variable format specification.
If you pass a parameter as an argument, and the subprogram tries to change it, you may get a runtime error.
Examples
If a
CHARACTER
statement explicitly specifies the length for a symbolic name, then the constant in the
PARAMETER
statement can be no longer than that length. Longer constants are truncated, and a warning is issued. The
CHARACTER
statement must appear before the
PARAMETER
statement.
If a
CHARACTER
statement uses
*(*)
to specify the length for a symbolic name, then the data in the
PARAMETER
statement are used to determine the length of the symbolic constant. The
CHARACTER
statement must appear before the
PARAMETER
statement.
Any symbolic name of a constant that appears in an expression e must have been defined previously in the same or a different
PARAMETER
statement in the same program unit.
Example 1: Some real, character, and logical parameters:
&
&
CHARACTER HEADING*10
LOGICAL T
PARAMETER ( EPSILON=1.0E-6, PI=3.141593,
HEADING=’IO Error #’,
T=.TRUE. )
…
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4
Example 2: Let the compiler count the characters:
CHARACTER HEADING*(*)
PARAMETER ( HEADING='I/O Error Number' )
…
Example 3: The alternate syntax, if the
–xl
flag is set:
PARAMETER FLAG1 = .TRUE.
The above statement is treated as:
LOGICAL FLAG1
PARAMETER (FLAG1 = .TRUE.)
An ambiguous statement that could be interpreted as either a
PARAMETER statement or an assignment statement is always taken to be the former, as long as either the
–xl
or
–xld
option is set.
Example: An ambiguous statement:
PARAMETER S = .TRUE.
With
-xl
, the above statement is a
PARAMETER
statement about the variable
S
.
PARAMETER S = .TRUE.
It is not an assignment statement about the variable
PARAMETERS
.
PARAMETERS = .TRUE.
Statements
197
4
4.53 PAUSE
The
PAUSE
statement suspends execution, and waits for you to type: go
.
Syntax
PAUSE [
str ] str
String of not more than 5 digits or a character constant
Description
The
PAUSE
statement suspends program execution temporarily, and waits for acknowledgment. On acknowledgment, execution continues.
If the argument string is present, it is displayed on the screen (written to stdout
), followed by the following message:
PAUSE. To resume execution, type: go
Any other input will terminate the program.
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4
After you type: go
, execution continues as if a
CONTINUE
statement is executed. See this example: demo% cat p.f
PRINT *, "Start"
PAUSE 1
PRINT *, "Ok"
END demo% f77 p.f p.f:
MAIN: demo% a.out
Start
PAUSE: 1
To resume execution, type: go
Any other input will terminate the program.
go
Execution resumed after PAUSE.
Ok demo%
If stdin
is not a tty
I/O device,
PAUSE
displays a message like this:
PAUSE: To resume execution, type: kill -15
pid
where pid is the process ID.
Example: stdin
not a tty
I/O device: demo% a.out < mydatafile
PAUSE: To resume execution, type: kill -15 20537 demo%
For the above example, type the following command line at a shell prompt in some other window. The window displaying the message cannot accept command input.
demo% kill -15 20537
Statements
199
4
4.54
POINTER
The
POINTER
♦ statement establishes pairs of variables and pointers.
Syntax
POINTER (
p1
,
v1
) [, (
p2
,
v2
) … ]
v1, v2 p1, p2
Pointer-based variables
Corresponding pointers
Description
Each pointer contains the address of its paired variable.
A pointer-based variable is a variable paired with a pointer in a
POINTER statement. A pointer-based variable is usually called just a based variable. The
pointer is the integer variable that contains the address.
Usage
Normal use of pointer-based variables involves the following steps. The first two steps can be in either order.
1. Define the pairing of the pointer-based variable and the pointer in a
POINTER
statement.
2. Define the type of the pointer-based variable.
The pointer itself is an integer type, but in general, it is safer if you not list it in an
INTEGER
statement.
3. Set the pointer to the address of an area of memory that has the appropriate size and type.
You do not normally do anything else with the pointer explicitly.
4. Reference the pointer-based variable.
Just use the pointer-based variable in normal FORTRAN 77 statements; the address of that variable is always taken from its associated pointer.
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Address and Memory
No storage for the variable is allocated when a pointer-based variable is defined, so you must provide an address of a variable of the appropriate type and size, and assign the address to a pointer, usually with the normal assignment statement or data statement.
There are three procedures used to manage memory with pointers:
•
LOC
—You can obtain the address from the intrinsic function
LOC()
.
•
MALLOC
—You can obtain both the area of memory and the address from the function
MALLOC()
.
•
FREE
—You can deallocate a region of memory previously allocated by
MALLOC()
by using the subroutine
FREE()
.
Subroutine
FREE()
The subroutine
FREE()
deallocates a region of memory previously allocated by
MALLOC()
. The argument given to
FREE()
must be a pointer previously returned by
MALLOC()
, but not already given to
FREE()
. The memory is returned to the memory manager, making it unavailable to the programmer.
Function
MALLOC()
The function
MALLOC()
allocates an area of memory and returns the address of the start of that area. The argument to the function is an integer specifying the amount of memory to be allocated, in bytes. If successful, it returns a pointer to the first item of the region; otherwise, it returns an integer 0. The region of memory is not initialized in any way—assume it is garbage.
Optimization and Pointers
Pointers have the side effect of reducing the assumptions that the global optimizer can make.
Compare:
•
Without pointers, if you call a subroutine or function, the optimizer knows that the call will change only variables in common or those passed as arguments to that call.
Statements
201
4
202
•
With pointers, this is no longer valid, since a routine can take the address of an argument and save it in a pointer in common for use in a subsequent call to itself or to another routine.
Therefore, the optimizer must assume that a variable passed as an argument in a subroutine or function call can be changed by any other call. Such an unrestricted use of pointers would degrade optimization for the vast majority of programs that do not use pointers.
Restrictions
The pointers are of type integer and are automatically typed that way by the compiler. You must not type them yourself.
A pointer-based variable cannot itself be a pointer.
The pointer-based variables can be of any type, including structures.
No storage is allocated when such a pointer-based variable is defined, even if there is a size specification in the type statement.
You cannot use a pointer-based variable as a dummy argument or in
COMMON
,
EQUIVALENCE
,
DATA
, or
NAMELIST
statements.
The dimension expressions for pointer-based variables must be constant expressions in main programs. In subroutines and functions, the same rules apply for pointer-based array variables as for dummy arguments—the expression can contain dummy arguments and variables in common. Any variables in the expressions must be defined with an integer value at the time the subroutine or function is called.
This implementation of
POINTER
follows more along the line of Cray, not
Fortran 90, although it does not follow Cray exactly.
The address cannot exceed the range of
INTEGER*4
. If the address expression is not in the range (-2147483648, 2147483647), then the results are unpredictable.
If you use an optimization level greater than
-O2
, you must write your programs with the following restrictions on the use of pointers:
•
Subroutines and functions are not permitted to save the address of any of their arguments between calls.
FORTRAN 77 Reference Manual
4
•
A function cannot return the address of any of its arguments, although it can return the value of a pointer argument.
•
Only those variables whose addresses are explicitly taken with the
LOC()
or
MALLOC()
functions can be referenced through a pointer.
Example: One kind of code that could cause problems if you optimize at a level greater than
-O2
:
COMMON A, B, C
POINTER ( P, V )
P = LOC(A) + 4 !
←
Possible problems if optimized
…
The compiler assumes that a reference through
P
can change
A
, but not
B
; this assumption could produce incorrect code.
Examples
Example 1: A simple
POINTER
statement:
POINTER ( P, V )
Here,
V
is a pointer-based variable, and
P
is its associated pointer.
Example 2: Using the
LOC()
function to get an address:
* ptr1.f: Assign an address via LOC()
POINTER ( P, V )
CHARACTER A*12, V*12
DATA A / 'ABCDEFGHIJKL' /
P = LOC( A )
PRINT *, V(5:5)
END
In the above example, the
CHARACTER
statement allocates 12 bytes of storage for
A
, but no storage for
V
; it merely specifies the type of
V
because
V
is a pointer-based variable. You then assign the address of
A
to
P
, so now any use of
V
refers to
A
by the pointer
P
. The program prints an
E
.
Statements
203
4
204
Example 3: Memory allocation for pointers, by
MALLOC
:
POINTER ( P1, X ), ( P2, Y ), ( P3, Z )
…
P1 = MALLOC ( 36 )
…
CALL FREE ( P1 )
…
In the above example, you get 36 bytes of memory from
MALLOC()
and then, after some other instructions, probably using that chunk of memory, tell
FREE()
to return those same 36 bytes to the memory manager.
Example 4: Get the area of memory and its address:
POINTER ( P, V )
CHARACTER V*12, Z*1
P = MALLOC( 12 )
…
END
In the above example, you obtain 12 bytes of memory from the function
MALLOC()
and assign the address of that block of memory to the pointer
P
.
Example 5: Dynamic allocation of arrays:
PROGRAM UsePointers
REAL X
POINTER ( P, X )
…
READ ( *,* ) Nsize !
Get the size.
P = MALLOC( Nsize )!
Allocate the memory.
…
CALL CALC ( X, Nsize )
…
END
SUBROUTINE CALC ( A, N )
REAL A(N)
…
! Use the array of whatever size.
RETURN
END
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4
This is a slightly more realistic example. The size might well be some large number, say, 10,000. Once that’s allocated, the subroutines perform their tasks, not knowing that the array was dynamically allocated.
Statements
205
206
4
Linked.f
Example 6: One way to use pointers to make a linked list in f77
:
STRUCTURE /NodeType/
INTEGER recnum
CHARACTER*3 label
INTEGER next
END STRUCTURE
RECORD /NodeType/ r, b
POINTER (pr,r), (pb,b) pb = malloc(12) pr = pb
!
Create the base record, b.
!
Make pr point to b.
NodeNum = 1
DO WHILE (NodeNum .LE. 4) !
Initialize/create records
IF (NodeNum .NE. 1) pr = r.next
CALL struct_creat(pr,NodeNum)
NodeNum = NodeNum + 1
END DO r.next = 0 pr = pb !
Show all records.
DO WHILE (pr .NE. 0)
PRINT *, r.recnum, " ", r.label
pr = r.next
END DO
END
SUBROUTINE struct_creat(pr,Num)
STRUCTURE /NodeType/
INTEGER recnum
CHARACTER*3 label
INTEGER next
END STRUCTURE
RECORD /NodeType/ r
POINTER (pr,r), (pb,b)
CHARACTER v*3(4)/'aaa', 'bbb', 'ccc', 'ddd'/ r.recnum = Num r.label = v(Num) pb = malloc(12) r.next = pb
RETURN
END
!
Initialize current record.
!
Create next record.
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4
demo% f77 -silent Linked.f
"Linked.f", line 6: Warning: local variable "b" never used
"Linked.f", line 31: Warning: local variable "b" never used demo% a.out
1 aaa
2 bbb
3 ccc
4 ddd demo%
Remember:
•
Do not optimize programs using pointers like this with
-O3
,
-O4,
or
-O5
.
•
The warnings can be ignored.
•
This is not the normal usage of pointers described at the start of this section.
4.55
The
statement writes from a list to stdout
.
Syntax
f
[,
iolist
]
grname f iolist grname
Format identifier
List of variables, substrings, arrays, records, …
Name of the namelist group
Description
The
statement accepts the following arguments.
Statements
207
4
208
Format Identifier
f is a format identifier and can be:
•
An asterisk (
*
), which indicates list-directed I/O. See Section 5.6, “List-
Directed I/O,” for details.
•
The label of a
FORMAT
statement that appears in the same program unit.
•
An integer variable name that has been assigned the label of a
FORMAT statement that appears in the same program unit.
•
A character expression or integer array that specifies the format string. The integer array is nonstandard. ♦
Output List
iolist can be empty or can contain output items or implied
DO
lists. The output items must be one of the following:
•
Variables
•
Substrings
•
Arrays
•
Array elements
•
Record fields
•
Any other expression
A simple unsubscripted array name specifies all of the elements of the array in memory storage order, with the leftmost subscript increasing more rapidly.
Namelist-Directed
The second form of the
statement is used to print the items of the specified namelist group. Here, grname is the name of a group previously defined by a
NAMELIST
statement.
Execution proceeds as follows:
1. The format, if specified, is established.
2. If the output list is not empty, data is transferred from the list to standard output.
If a format is specified, data is edited accordingly.
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4
3. In the second form of the
statement, data is transferred from the items of the specified namelist group to standard output.
Restrictions
Output from an exception handler is unpredictable. If you make your own exception handler, do not do any FORTRAN 77 output from it. If you must do some, then call abort right after the output. Doing so reduces the relative risk of a program freeze. FORTRAN 77 I/O from an exception handler amounts to recursive I/O. See the next point.
Recursive I/O does not work reliably. If you list a function in an I/O list, and if that function does I/O, then during runtime, the execution may freeze, or some other unpredictable problem may occur. This risk exists independent of parallelization.
Example: Recursive I/O fails intermittently:
PRINT *, x, f(x) !
Not allowed,
f()
does I/O.
END
FUNCTION F(X)
PRINT *, X
RETURN
END
Examples
Example 1: Formatted scalars:
CHARACTER TEXT*16
PRINT 1, NODE, TEXT
1 FORMAT ( I2, A16 )
Example 2: List-directed array:
PRINT *, I, J, ( VECTOR(I), I = 1, 5 )
Statements
209
4
Example 3: Formatted array:
INTEGER VECTOR(10)
PRINT '( 12 I2 )', I, J, VECTOR
Example 4: Namelist:
CHARACTER LABEL*16
REAL QUANTITY
INTEGER NODE
NAMELIST /SUMMARY/ LABEL, QUANTITY, NODE
PRINT SUMMARY
4.56
PROGRAM
The
PROGRAM
statement identifies the program unit as a main program.
Syntax
PROGRAM
pgm pgm
Symbolic name of the main program
Description
For the loader, the main program is always named
MAIN
. The
PROGRAM statement serves only the person who reads the program.
Restrictions
The
PROGRAM
statement can appear only as the first statement of the main program.
The name of the program cannot be:
•
The same as that of an external procedure or common block
•
MAIN
(all uppercase), or a runtime error results
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FORTRAN 77 Reference Manual
The name of the program can be the same as a local name in the main program.♦ The FORTRAN 77 Standard does not allow this practice.
4
Example
Example: A
PROGRAM
statement:
PROGRAM US_ECONOMY
NVARS = 2
NEQS = 2
…
4.57
READ
The
READ
statement reads data from a file or the keyboard to items in the list.
If you use this statement for tapes, we recommend the
TOPEN()
routines instead, because they are more reliable.
Syntax f u ios rn
READ( [ UNIT=]
u
[, [ FMT=]
f
] [, IOSTAT=
ios
] [, REC=
rn
]
[, END=
s
] [, ERR=
s
] )
iolist
READ
f
[,
iolist
]
READ([UNIT=]
u
, [NML=]
grname
[,IOSTAT=
ios
] [,END=
s
] [,ERR=
s
] )
READ
grname
An alternate to the
UNIT=
u,
REC
=rn form is as follows: ♦
READ(
u
'
rn
… )
iolist
Unit identifier of the unit connected to the file
Format identifier
I/O status specifier
Record number to be read
Statements
211
4
212
s iolist grname
Statement label for end of file processing
List of variables
Name of a namelist group
The options can be specified in any order.
Description
The
READ
statement accepts the following arguments.
Unit Identifier
u is either an external unit identifier or an internal file identifier.
An external unit identifier must be one of these:
•
A nonnegative integer expression
•
An asterisk (
*
), identifying stdin
, normally connected to the keyboard
If the optional characters
UNIT=
are omitted from the unit specifier, then u must be the first item in the list of specifiers.
Format Identifier
f is a format identifier and can be:
•
An asterisk (
*
), indicating list-directed I/O. See Section 5.6, “List-Directed
I/O,” for details.
•
A label of a
FORMAT
statement that appears in the same program unit
•
An integer variable name that has been assigned the label of a
FORMAT statement that appears in the same program unit
•
A character expression or integer array specifying the format string. This is called a runtime format or a variable format. The integer array is nonstandard. ♦
If the optional characters,
FMT=
, are omitted from the format specifier, then f must appear as the second argument for a formatted read; otherwise, it must not appear at all.
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4
Unformatted data transfer from internal files and terminal files is not allowed, hence, f must be present for such files.
List-directed data transfer from direct-access and internal files is allowed; hence, f can be an asterisk for such files. ♦
If a file is connected for formatted I/O, unformatted data transfer is not allowed, and vice versa.
I/O Status Specifier
ios must be an integer variable or an integer array element.
Record Number
rn must be a positive integer expression, and can be used for direct-access files only. rn can be specified for internal files. ♦
End-of-File Specifier
s must be the label of an executable statement in the same program unit in which the
READ
statement occurs.
The
END=
s and
REC=
rn specifiers can be present in the same
READ
statement. ♦
Error Specifier
s must be the label of an executable statement in the same program unit in which the
READ
statement occurs.
Input List
iolist can be empty or can contain input items or implied
DO
lists. The input items can be any of the following:
•
Variables
•
Substrings
•
Arrays
•
Array elements
•
Record fields
Statements
213
4
214
A simple unsubscripted array name specifies all of the elements of the array in memory storage order, with the leftmost subscript increasing more rapidly.
Namelist-Directed
READ
The third and fourth forms of the
READ
statement are used to read the items of the specified namelist group, and grname is the name of the group of variables previously defined in a
NAMELIST
statement.
Execution
Execution proceeds as follows:
1. The file associated with the specified unit is determined.
The format, if specified, is established. The file is positioned appropriately prior to the data transfer.
2. If the input list is not empty, data is transferred from the file to the corresponding items in the list.
The items are processed in order as long as the input list is not exhausted.
The next specified item is determined and the value read is transmitted to it.
Data editing in formatted
READ
is done according to the specified format.
3. In the third and fourth forms of namelist-directed
READ
, the items of the specified namelist group are processed according to the rules of
namelist
-directed input.
4. The file is repositioned appropriately after data transfer.
5. If ios is specified and no error occurred, it is set to zero.
ios is set to a positive value, if an error or end of file was encountered.
6. If s is specified and end of file was encountered, control is transferred to s.
7. If s is specified and an error occurs, control is transferred to s
.
There are two forms of
READ
:
READ
f
[,
iolist
]
READ ( [ NML= ]
grname
)
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4
The above two forms operate the same way as the others, except that reading from the keyboard is implied.
Execution has the following differences:
•
When the input list is exhausted, the cursor is moved to the start of the line following the input. For an empty input list, the cursor is moved to the start of the line following the input.
•
If an end-of-line,
CR
, or
NL
is reached before the input list is satisfied, input continues from the next line.
•
If an end-of-file (Control-D) is received before the input list is satisfied, input stops, and unsatisfied items of the input list remain unchanged.
If u specifies an external unit that is not connected to a file, an implicit
OPEN operation is performed which is equivalent to opening the file with the options in the following example:
OPEN(
u
, FILE='FORT.u', STATUS='OLD',
& ACCESS='SEQUENTIAL', FORM=
fmt
)
The value of fmt is
'FORMATTED'
or
'UNFORMATTED'
accordingly, as the read is formatted or unformatted.
A simple unsubscripted array name specifies all of the elements of the array in memory storage order, with the leftmost subscript increasing more rapidly.
An attempt to read the record of a direct-access file that has not been written, causes all items in the input list to become undefined.
The record number count starts from one.
Namelist-directed input is permitted on sequential access files only.
Statements
215
4
216
Examples
Example 1: Formatted read, trap I/O errors, EOF, and I/O status:
READ( 1, 2, ERR=8, END=9, IOSTAT=N ) X, Y
…
8 WRITE( *, * ) 'I/O error # ', N, ', on 1'
STOP
9 WRITE( *, * ) 'EoF on 1'
RETURN
END
Example 2: Direct, unformatted read, trap I/O errors, and I/O status:
…
READ( 1, REC=3, IOSTAT=N, ERR=8 ) V
…
4 CONTINUE
RETURN
8 WRITE( *, * ) 'I/O error # ', N, ', on 1'
END
Example 3: List-directed read from keyboard: or
READ( *, * ) A, V
READ *, A, V
Example 4: Formatted read from an internal file:
1
CHARACTER CA*16 / 'abcdefghijklmnop' /, L*8, R*8
READ( CA, 1 ) L, R
FORMAT( 2 A8 )
Example 5: Read an entire array:
DIMENSION V(5)
READ( 3, '(5F4.1)') V
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4
Example 6: Namelist-directed read:
CHARACTER SAMPLE*16
LOGICAL NEW*4
REAL DELTA*4
NAMELIST /G/ SAMPLE, NEW, DELTA
…
READ( 1, G ) or or
READ( UNIT=1, NML=G )
READ( 1, NML=G )
4.58
REAL
The
REAL
statement specifies the type of a symbolic constant, variable, array, function, or dummy function to be real, and optionally specifies array dimensions and size, and initializes with values.
Syntax
REAL [*
len
[,]]
v
[ *
len
[/
c
/]] [,
v
[*
len
[/
c
/]] …
v
Name of a variable, symbolic constant, array, array declarator, function, or dummy function
len
Either 4, 8, or 16 (SPARC only), the length in bytes of the symbolic constant, variable, array element, or function
c
List of constants for the immediately preceding name
Description
Following are descriptions for
REAL
,
REAL*4
,
REAL*8
, and
REAL*16
.
REAL
For a declaration such as
REAL W
, the variable
W
is usually a
REAL*4
element in memory, interpreted as a real number. For more details, see the next section,
“Default Size.”
Statements
217
4
218
REAL*4
♦
For a declaration such as
REAL*4 W
, the variable
W
is always a
REAL*4 element in memory, interpreted as a single-width real number.
REAL*8
♦
For a declaration such as
REAL*8 W
, the variable
W
is always a
REAL*8 element in memory, interpreted as a double-width real number.
REAL*16
♦
(SPARC only) For a declaration such as
REAL*16 W
, the variable
W
is always an element of type
REAL*16
in memory, interpreted as a quadruple-width real.
Default Size
If you specify the size as 4, 8, or 16, you get what you specify; if you do not specify the size, you get the default size.
The default size for a declaration such as
REAL X
, depends on the
–r8
option:
•
If
–r8
or
-dbl
is on the f77
command line, then for declarations such as
REAL X
, the compiler allocates 8 bytes, and does 8-byte arithmetic. If
–r8
or
-dbl
is not on the f77
command line, then the compiler allocates 4 bytes.
•
If you put both
–i2
and
–r8
on the f77
command line, the results are unpredictable.
Examples
Example 1: Simple real scalars—each of these statements is generally equivalent to the others, but the first is different if you compile with
-r8
:
REAL U, V
REAL*4 U, V
REAL U*4, V*4
Do not use all three statements in the same program unit.
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4.59
RECORD
4
Example 2: Initialize scalars (
REAL*16
is for SPARC only):
REAL U/ 1.0 /, V/ 4.3 /, D*8/ 1.0 /, Q*16/ 4.5 /
Example 3: Specify dimensions for some real arrays:
REAL A(10,100), V(10)
REAL X*4(10), Y(10)*4
Example 4: Initialize some arrays:
REAL A(10,100) / 1000 * 0.0 /, B(2,2) / 1.0, 2.0, 3.0, 4.0 /
Example 5: Double and quadruple precision (
REAL*16
is for SPARC only):
REAL*8 R
REAL*16 Q
DOUBLE PRECISION D
In the above example,
D
and
R
are both double precision;
Q
is quadruple precision.
The
RECORD
♦ statement defines variables to have a specified structure, or arrays to be arrays of variables with such structures.
Syntax
RECORD /
struct-name
/
record-list
[,/
struct-name
/
record-list
]…
struct-name
Name of a previously declared structure
record-list
List of variables, arrays, or array declarators
Statements
219
4
Description
A structure is a template for a record. The name of the structure is included in the
STRUCTURE
statement, and once a structure is thus defined and named, it can be used in a
RECORD
statement.
The record is a generalization of the variable or array: where a variable or array has a type, the record has a structure. Where all the elements of an array must be of the same type, the fields of a record can be of different types.
The
RECORD
line is part of an inherently multiline group of statements, and neither the
RECORD
line nor the
END RECORD
line has any indication of continuation. Do not put a nonblank in column six, nor an
&
in column one.
Restrictions
Each record is allocated separately in memory.
Initially, records have undefined values.
Records, record fields, record arrays, and record-array elements are allowed as arguments and dummy arguments. When you pass records as arguments, their fields must match in type, order, and dimension. The record declarations in the calling and called procedures must match.
Within a union declaration, the order of the map fields is not relevant.
Record fields are not allowed in
COMMON
statements.
Records and record fields are not allowed in
DATA
,
EQUIVALENCE
,
NAMELIST
,
PARAMETER
,
AUTOMATIC
,
STATIC
, or
SAVE
statements. To initialize records and record fields, use the
STRUCTURE
statement. See Section 4.66,
“STRUCTURE.”
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4
Example
Example 1: Declare some items to be records of a specified structure:
STRUCTURE /PRODUCT/
INTEGER*4 ID
CHARACTER*16 NAME
CHARACTER*8 MODEL
REAL*4 COST
REAL*4 PRICE
END STRUCTURE
RECORD /PRODUCT/ CURRENT, PRIOR, NEXT, LINE(10)
…
Each of the three variables
CURRENT
,
PRIOR
, and
NEXT
is a record which has the
PRODUCT
structure, and
LINE
is an array of 10 such records.
Example 2: Define some fields of records, then use them:
STRUCTURE /PRODUCT/
INTEGER*4 ID
CHARACTER*16 NAME
CHARACTER*8 MODEL
REAL*4 COST
REAL*4 PRICE
END STRUCTURE
RECORD /PRODUCT/ CURRENT, PRIOR, NEXT, LINE(10)
CURRENT.ID = 82
PRIOR.NAME = "CacheBoard"
NEXT.PRICE = 1000.00
LINE(2).MODEL = "96K"
PRINT 1, CURRENT.ID, PRIOR.NAME, NEXT.PRICE, LINE(2).MODEL
1 FORMAT(1X I5/1X A16/1X F8.2/1X A8)
END
The above program produces the following output:
82
CacheBoard
1000.00
96K
Statements
221
4
4.60
RETURN
A
RETURN
statement returns control to the calling program unit.
Syntax
RETURN [
e
]
e
Expression of type
INTEGER
or
REAL
Description
Execution of a
RETURN
statement terminates the reference of a function or subroutine.
Execution of an
END
statement in a function or a subroutine is equivalent to the execution of a
RETURN
statement. ♦
The expression e
is evaluated and converted to integer, if required.
e
defines the ordinal number of the alternate return label to be used. Alternate return labels are specified as asterisks (or ampersands) ♦ in the
SUBROUTINE statement.
If e is not specified, or the value of e is less than one or greater than the number of asterisks or ampersands in the
SUBROUTINE
statement that contains the
RETURN
statement, control is returned normally to the statement following the
CALL
statement that invoked the subroutine.
If the value of e
is between one and the number of asterisks (or ampersands) in the
SUBROUTINE
statement, control is returned to the statement identified by the e th
alternate. A
RETURN
statement can appear only in a function subprogram or subroutine.
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4
Examples
Example 1: Standard return:
CHARACTER*25 TEXT
TEXT = "Some kind of minor catastrophe"
…
CALL OOPS ( TEXT )
STOP
END
SUBROUTINE OOPS ( S )
CHARACTER S* 32
WRITE (*,*) S
RETURN
END
Example 2: Alternate return:
CALL RANK ( N, *8, *9 )
WRITE (*,*) 'OK - Normal Return'
STOP
8 WRITE (*,*) 'Minor - 1st alternate return'
STOP
9 WRITE (*,*) 'Major - 2nd alternate return'
END
SUBROUTINE RANK (N, *,*)
IF ( N .EQ. 0 ) RETURN
IF ( N .EQ. 1 ) RETURN 1
RETURN 2
END
4.61
REWIND
REWIND
positions the file associated with the specified unit to its initial point.
If you use this statement for tapes, we recommend the
TOPEN()
routines instead, because they are more reliable.
Statements
223
4
Syntax
Description
The options can be specified in any order.
Rewinding a unit not associated with any file has no effect. Likewise,
REWIND in a terminal file has no effect either.
We do not recommend using a
REWIND
statement on a direct-access file, as the execution is not defined in the FORTRAN 77 Standard, and is unpredictable.
Examples
REWIND
u
REWIND ( [ UNIT=]
u
[, IOSTAT=
ios
] [, ERR=
s
])
u
Unit identifier of an external unit connected to the file
u must be connected for sequential access, or append access.
ios s
I/O specifier, an integer variable or an integer array element
Error specifier: s must be the label of an executable statement in the same program in which this
REWIND
statement occurs. The program control is transferred to this label in case of an error during the execution of the
REWIND
statement.
Example 1: Simple form of unit specifier:
ENDFILE 3
REWIND 3
READ (3,'(I2)') I
REWIND 3
READ (3,'(I2)')I
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4
Example 2:
REWIND
with the
UNIT=
u form of unit specifier and error trap:
INTEGER CODE
…
REWIND (UNIT = 3)
REWIND (UNIT = 3, IOSTAT = CODE, ERR = 100)
…
100 WRITE (*,*) 'error in rewinding'
STOP
4.62
SAVE
The
SAVE
statement prevents items in a subprogram from becoming undefined after the
RETURN
or
END
statements are executed.
Syntax
SAVE [
v
[,
v
] … ]
v
Name of an array, variable, or common block (enclosed in slashes), occurring in a subprogram
Description
All variables to be saved are placed in an internal static area. All common blocks are saved by allocating a static area. Therefore, common block names specified in
SAVE
statements are just ignored.
A
SAVE
statement is optional in the main program and has no effect.
A
SAVE
with no list saves everything that can be saved.
SAVE
/
STATIC
Local variables and arrays are static by default, so in general, using these constructs eliminates the need for
SAVE
. You can still use
SAVE
to ensure portability.
Also,
SAVE
is safer if you leave a subprogram by some way other than a
RETURN
.
Statements
225
4
Restrictions
The following constructs must not appear in a
SAVE
statement:
•
Variables or arrays in a common block
•
Dummy argument names
•
Record names
•
Procedure names
•
Automatic variables or arrays
Example
Example: A
SAVE
statement:
SUBROUTINE FFT
DIMENSION A(1000,1000), V(1000)
SAVE A
…
RETURN
END
4.63 Statement Function
A statement function statement is a function-like declaration, made in a single statement.
Syntax d e fun
( [
d
[,
d
] … ] ) =
e fun
Name of statement function being defined
Statement function dummy argument
Expression. e can be any of the types arithmetic, logical, or character.
Description
If a statement function is referenced, the defined calculations are inserted.
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4
Example: The following statement is a statement function:
ROOT( A, B, C ) = (-B + SQRT(B**2-4.0*A*C))/(2.0*A)
The statement function argument list indicates the order, number, and type of arguments for the statement function.
A statement function is referenced by using its name, along with its arguments, as an operand in an expression.
Execution proceeds as follows:
1. If they are expressions, actual arguments are evaluated.
2. Actual arguments are associated with corresponding dummy arguments.
3. The expression e, the body of a statement function, is evaluated.
4. If the type of the above result is different from the type of the function name, then the result is converted.
5. Return the value.
The resulting value is thus available to the expression that referenced the function.
Restrictions
Note these restrictions:
•
A statement function must appear only after the specification statements and before the first executable statement of the program unit in which it is referenced.
•
A statement function is not executed at the point where it is specified. It is executed, as any other, by the execution of a function reference in an expression.
•
The type conformance between fun and e are the same as those for the assignment statement. The type of fun and e can be different, in which case e is converted to the type of fun.
•
The actual arguments must agree in order, number, and type with corresponding dummy arguments.
Statements
227
228
4
•
The same argument cannot be specified more than once in the argument list.
•
The statement function must be referenced only in the program unit that contains it.
•
The name of a statement function cannot be an actual argument. Nor can it appear in an
EXTERNAL
statement.
•
The type of the argument is determined as if the statement function were a whole program unit in itself.
•
Even if the name of a statement function argument is the same as that of another local variable, the reference is considered a dummy argument of the statement function, not the local variable of the same name.
•
The length specification of a character statement function or its dummy argument of type
CHARACTER
must be an integer constant expression.
•
A statement function cannot be invoked recursively.
Examples
Example 1: Arithmetic statement function:
PARAMETER ( PI=3.14159 )
REAL RADIUS, VOLUME
SPHERE ( R ) = 4.0 * PI * (R**3) / 3.0
READ *, RADIUS
VOLUME = SPHERE( RADIUS )
…
Example 2: Logical statement function:
LOGICAL OKFILE
INTEGER STATUS
OKFILE ( I ) = I .LT. 1
READ( *, *, IOSTAT=STATUS ) X, Y
IF ( OK FILE(STATUS) ) CALL CALC ( X, Y, A )
…
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4
Example 3: Character statement function:
CHARACTER FIRST*1, STR*16
FIRST(S) = S(1:1)
READ( *, * ) STR
IF ( FIRST(STR) .LT. " " ) CALL CONTROL ( S, A )
…
4.64
STATIC
The
STATIC
♦ statement ensures that the specified items are stored in static memory.
Syntax
STATIC
list list
List of variables and arrays
Description
To deal with the problem of local variables becoming undefined between invocations, f77
classifies every variable as either static or automatic, with all local variables being static by default.
For static variables, there is exactly one copy of each datum, and its value is retained between calls. You can also explicitly define variables as static or automatic in a
STATIC
or
AUTOMATIC
statement, or in any type statement or
IMPLICIT
statement.
Local variables and arrays are static by default, so in general, these constructs eliminate the need for
SAVE
. You can still use
SAVE
to ensure portability.
Also,
SAVE
is safer if you leave a subprogram by some way other than a
RETURN
.
Statements
229
4
Also note that:
•
Arguments and function values are automatic.
•
A
STATIC
statement and a type statement cannot be combined to make a
STATIC
type statement. For example, the statement:
STATIC REAL X !
Not what you might expect
does not declare the variable
X
to be both
STATIC
and
REAL
; it declares the variable
REALX
to be
STATIC
.
Example
STATIC A, B, C
REAL P, D, Q
STATIC P, D, Q
IMPLICIT STATIC (X-Z)
4.65
STOP
The
STOP
statement terminates execution of the program.
Syntax
STOP [ [
str
]
str
String of no more that 5 digits or a character constant
Description
The argument str is displayed when the program stops.
If str is not specified, no message is displayed.
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FORTRAN 77 Reference Manual
Examples
Example 1: Integer: stop 9
The above statement displays:
STOP: 9
Example 2: Character: stop 'oyvay'
The above statement displays:
STOP: oyvay
Example 3: Nothing after the stop
: stop
The above statement displays nothing.
4.66
STRUCTURE
The
STRUCTURE
♦ statement organizes data into structures.
4
Statements
231
4
232
Syntax
STRUCTURE [/
structure-name
/] [
field-list
]
field-declaration
[
field-declaration
]
…
[
field-declaration
]
END STRUCTURE
structure-name field-list field-declaration
Name of the structure
List of fields of the specified structure
Field of the record
Each field declaration can be one of the following:
•
A substructure—either another structure declaration, or a record that has been previously defined
•
A union declaration
•
A type declaration, which can include initial values
Description
A
STRUCTURE
statement defines a form for a record by specifying the name, type, size, and order of the fields that constitute the record. Optionally, it can specify the initial values.
A structure is a template for a record. The name of the structure is included in the
STRUCTURE
statement, and once a structure is thus defined and named, it can be used in a
RECORD
statement.
The record is a generalization of the variable or array—where a variable or array has a type, the record has a structure. Where all the elements of an array must be of the same type, the fields of a record can be of different types.
Restrictions
The name is enclosed in slashes and is optional in nested structures only.
If slashes are present, a name must be present.
FORTRAN 77 Reference Manual
4
You can specify the field-list within nested structures only.
There must be at least one field-declaration.
Each structure-name must be unique among structures, although you can use structure names for fields in other structures or as variable names.
The only statements allowed between the
STRUCTURE
statement and the
END
STRUCTURE
statement are field-declaration statements and
PARAMETER statements. A
PARAMETER
statement inside a structure declaration block is equivalent to one outside.
Restrictions for Fields
Fields that are type declarations use the identical syntax of normal
FORTRAN 77 type statements, and all f77
types are allowed, subject to the following rules and restrictions:
•
Any dimensioning needed must be in the type statement. The
DIMENSION statement has no effect on field names.
•
You can specify the pseudonyme
%FILL
for a field name. The
%FILL
is provided for compatibility with other versions of FORTRAN 77. It is not needed in f77
because the alignment problems are taken care of for you. It is a useful feature if you want to make one or more fields not referenceable in some particular subroutine. The only thing that
%FILL
does is provide a field of the specified size and type, and preclude referencing it.
•
You must explicitly type all field names. The
IMPLICIT
statement does not apply to statements in a
STRUCTURE
declaration, nor do the implicit
I,J,K,L,M,N
rules apply.
•
You cannot use arrays with adjustable or assumed size in field declarations, nor can you include passed-length
CHARACTER
declarations.
In a structure declaration, the offset of field n is the offset of the preceding field, plus the length of the preceding field, possibly corrected for any adjustments made to maintain alignment.
You can initialize a field that is a variable, array, substring, substructure, or union.
Statements
233
4
Examples
Example 1: A structure of five fields:
STRUCTURE /PRODUCT/
INTEGER*4 ID/ 99 /
CHARACTER*16 NAME
CHARACTER*8 MODEL/ 'Z' /
REAL*4 COST
REAL*4 PRICE
END STRUCTURE
RECORD /PRODUCT/ CURRENT, PRIOR, NEXT, LINE(10)
In the above example, a structure named
PRODUCT
is defined to consist of the fields
ID
,
NAME
,
MODEL
,
COST
, and
PRICE
. Each of the three variables,
CURRENT
,
PRIOR
, and
NEXT
, is a record which has the
PRODUCT
structure, and
LINE
is an array of 10 such records. Every such record has its
ID
initially set to
99, and its
MODEL
initially set to
Z
.
Example 2: A structure of two fields:
STRUCTURE /VARLENSTR/
INTEGER*4 NBYTES
CHARACTER A*25
END STRUCTURE
RECORD /VARLENSTR/ VLS
VLS.NBYTES = 0
The above structure matches the one used by the pc
Pascal compiler from
SunSoft for varying length strings. The
25
is arbitrary.
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4.67
SUBROUTINE
The
SUBROUTINE
statement identifies a named program unit as a subroutine, and specifies arguments for it.
Syntax
SUBROUTINE
sub
[ ( [
fd
[,
fd
] … ])]
sub
Name of subroutine subprogram
d
Variable name, array name, record name, or dummy procedure name, an asterisk, or an ampersand
Description
A subroutine subprogram must have a
SUBROUTINE
statement as the first statement. A subroutine can have any other statements, except a
BLOCK DATA
,
FUNCTION
,
PROGRAM
, or another
SUBROUTINE
statement.
sub is the name of a subroutine and is a global name, and must not be the same as any other global name such as a common block name or a function name.
Nor can it be the same as any local name in the same subroutine.
d is the dummy argument, and multiple dummy arguments are separated by commas. d can be one of the following:
•
Variable name
•
Array name
•
Dummy procedure name
•
Record name
•
Asterisk (
*
) or an ampersand (
&
) ♦
The dummy arguments are local to the subroutine and must not appear in any of the following statements, except as a common block name:
•
EQUIVALENCE
•
PARAMETER
•
SAVE
•
STATIC
•
AUTOMATIC
•
INTRINSIC
Statements
235
236
4
•
DATA
•
COMMON
The actual arguments in the
CALL
statement that references a subroutine must agree with the corresponding formal arguments in the
SUBROUTINE
statement, in order, number, and type. An asterisk (or an ampersand) in the formal argument list denotes an alternate return label. A
RETURN
statement in this procedure can specify the ordinal number of the alternate return to be taken.
Examples
Example 1: A variable and array as parameters:
SUBROUTINE SHR ( A, B )
CHARACTER A*8
REAL B(10,10)
…
RETURN
END
Example 2: Standard alternate returns:
In this example, the
RETURN 1 statement refers to the first alternate return label (first
*
).
The
RETURN 2
statement refers to the second alternate return label (second
*
) specified in the
SUBROUTINE
statement.
PROGRAM TESTALT
CALL RANK ( N, *8, *9 )
WRITE (*,*) 'OK - Normal Return [n=0]'
STOP
8 WRITE (*,*) 'Minor - 1st alternate return [n=1]'
STOP
9 WRITE (*,*) 'Major - 2nd alternate return [n=2]'
END
SUBROUTINE RANK ( N, *, * )
IF ( N .EQ. 0 ) RETURN
IF ( N .EQ. 1 ) RETURN 1
RETURN 2
END
Example 3: Nonstandard alternate returns: ♦
CALL SUB(…, &
label
, …)
FORTRAN 77 Reference Manual
is treated as:
CALL SUB(…, *
label
, …)
4.68
TYPE
The
TYPE
♦ statement writes to stdout
.
Syntax
TYPE f [,
iolist
] or:
TYPE grname
f iolist grname
Format identifier
List of output variables
Name of the namelist
group
Description
The
TYPE
statement is provided for compatibility with older versions of
FORTRAN 77, and is equivalent to the following:
•
f [, iolist ]
•
grname
•
WRITE(*,
f
)
[ iolist ]
•
WRITE(*,
grname
)
Examples
Example 1: Formatted output:
INTEGER V(5)
TYPE 1, V
1 FORMAT( 5 I3 )
4
Statements
237
4
Example 2: Namelist output:
CHARACTER S*16
INTEGER N
NAMELIST /G/ N, S
…
TYPE G
4.69 The Type Statement
The type statement specifies the data type of items in the list, optionally specifies array dimensions, and initializes with values.
Syntax type v
[/
clist
/] [,
v
[/
clist
/]…
v
Variable name, array name, array declarator, symbolic name of a constant, statement function or function subprogram name
clist
List of constants. There are more details about clist in the section on the
DATA
statement.
type can be preceded by either
AUTOMATIC
or
STATIC
.
type can be one of the following type specifiers:
BYTE
♦
CHARACTER
CHARACTER*
n
CHARACTER*(*)
COMPLEX
COMPLEX*8
COMPLEX*16
♦
♦
COMPLEX*32
(SPARC only)
DOUBLE COMPLEX
♦
♦
DOUBLE PRECISION
INTEGER
INTEGER*2
INTEGER*4
INTEGER*8
♦
♦
♦
LOGICAL
LOGICAL*1
LOGICAL*2
♦
♦
LOGICAL*4
LOGICAL*8
♦
♦
REAL
REAL*4
REAL*8
♦
♦
REAL*16
(SPARC only)
♦
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4
n, as in
CHARACTER*
n, must be greater than 0.
Description
A type statement can be used to:
•
Confirm or to override the type established by default or by the
IMPLICIT statement
•
Specify dimension information for an array, or confirm the type of an intrinsic function
•
Override the length by one of the acceptable lengths for that data type
A type statement can assign initial values to variables, arrays, or record fields by specifying a list of constants (clist) as in a
DATA
statement. ♦
The general form of a type statement is:
type VariableName
/
constant
/ … or:
type ArrayName
/
constant, … / or:
type ArrayName
/
r*constant
/ where r is a repeat factor.
Example: Various type statements:
CHARACTER LABEL*12 / 'Standard' /
COMPLEX STRESSPT / ( 0.0, 1.0 ) /
INTEGER COUNT / 99 /, Z / 1 /
REAL PRICE / 0.0 /, COST / 0.0 /
REAL LIST(8) / 0.0, 6*1.0, 0.0 /
When you initialize a data type, remember the following restrictions:
•
For a simple variable, there must be exactly one constant.
•
If any element of an array is initialized, all must be initialized.
Statements
239
4
240
•
You can use an integer as a repeat factor, followed by an asterisk (
*
), followed by a constant. In the example above, six values of 1.0 are stored into array elements 2, 3, 4, 5, 6, and 7 of
LIST
.
•
If a variable or array is declared
AUTOMATIC
, then it cannot be initialized.
•
A pointer-based variable or array cannot be initialized. For example:
INTEGER Z / 4 /
POINTER ( x, Z )
Restrictions
A symbolic name can appear only once in type statements in a program unit.
A type statement must precede all executable statements.
Example
In this case, the compiler issues a warning message, and
Z
is not initialized.
If a variable or array is not initialized, its values are undefined.
If such initialization statements involve variables in
COMMON
, and the
–ansi compiler flag is set, then a warning is issued.
Example: The type statement:
INTEGER*2 I, J/0/
REAL*4 PI/3.141592654/,ARRAY(10)/5*0.0,5*1.0/
CHARACTER*10 NAME
CHARACTER*10 TITLE/'Heading'/
In the above example:
•
J
is initialized to
0
•
PI
is initialized to
3.141592654
•
The first five elements of
ARRAY
are initialized to
0.0
•
The second five elements of
ARRAY
are initialized to
1.0
•
TITLE
is initialized to
'Heading'
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4
4.70
UNION
and
MAP
The
UNION
♦ statement defines groups of fields that share memory at runtime.
Syntax
The syntax of a
UNION
declaration is as follows:
UNION
map-declaration map-declaration
[map-declaration]
...
END UNION
The syntax of a
MAP
declaration is:
MAP
field-declaration
[
field-declaration
]
...
[
field-declaration
]
END MAP
Description
A
MAP
statement defines alternate groups of fields in a union. During execution, one map at a time is associated with a shared storage location.
When you reference a field in a map, the fields in any previous map become undefined, and are succeeded by the fields in the map of the newly referenced field. Also:
•
A
UNION
declaration can appear only within a
STRUCTURE
declaration.
•
The amount of memory used by a union is that of its biggest map.
•
Within a
UNION
declaration, the order of the
MAP
statements is not relevant.
The
UNION
line is part of an inherently multiline group of statements, and neither the
UNION
line nor the
END UNION
line has any special indication of continuation. You do not put a nonblank in column six, nor an
&
in column one.
Statements
241
242
4
Each field-declaration in a map declaration can be one of the following:
•
Structure declaration
•
Record
•
Union declaration
•
Declaration of a typed data field
Example
Declare the structure
/STUDENT/
to contain either
NAME
,
CLASS
, and
MAJOR, or
NAME
,
CLASS
,
CREDITS
, and
GRAD_DATE
:
STRUCTURE /STUDENT/
CHARACTER*32 NAME
INTEGER*2 CLASS
UNION
MAP
CHARACTER*16 MAJOR
END MAP
MAP
INTEGER*2 CREDITS
CHARACTER*8 GRAD_DATE
END MAP
END UNION
END STRUCTURE
RECORD /STUDENT/ PERSON
In the above example, the variable
PERSON
has the structure
/STUDENT/
, so:
•
PERSON.MAJOR
references a field from the first map;
PERSON.CREDITS
references a field from the second map.
•
If the variables of the second map field are initialized, and then the program references the variable
PERSON.MAJOR
, the first map becomes active, and the variables of the second map become undefined.
FORTRAN 77 Reference Manual
4
4.71
VIRTUAL
The
VIRTUAL
♦ statement is treated the same as the
DIMENSION
statement.
Syntax
VIRTUAL
a
(
d
) [,
a
(
d
) ] …
a a(d)
Name of an array
Specifies the dimension of the array. It is a list of 1 to 7 declarators separated by commas
Description
The
VIRTUAL
statement has the same form and effect as the
DIMENSION statement. It is included for compatibility with older versions of FORTRAN 77.
Example
VIRTUAL M(4,4), V(1000)
…
END
4.72
VOLATILE
The
VOLATILE
♦ statement prevents optimization on the specified items.
Syntax
VOLATILE
nlist
nlist List of variables, arrays, or common blocks
Statements
243
4
Description
The
VOLATILE
statement prevents optimization on the items in the list.
Programs relying on it are usually nonportable.
Example
Example:
VOLATILE
: ♦
PROGRAM FFT
INTEGER NODE*2, NSTEPS*2
REAL DELTA, MAT(10,10), V(1000), X, Z
COMMON /INI/ NODE, DELTA, V
…
VOLATILE V, Z, MAT, /INI/
…
EQUIVALENCE ( X, V )
…
In the above example, the array
V
, the variable
Z
, and the common block
/INI/
are explicitly specified as
VOLATILE
. The variable
X
is
VOLATILE through an equivalence.
4.73
WRITE
The
WRITE
statement writes data from the list to a file.
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Syntax f ios rn s
WRITE( [ UNIT=]
u
[, [FMT=]
f
] [, IOSTAT=
ios
] [, REC=
rn
]
[, ERR=
s
] )
iolist
WRITE( [ UNIT= ]
u
, [ NML= ]
grname
[, IOSTAT=
ios
] [, ERR=
s
] )
u
Unit identifier of the unit connected to the file
iolist grname
Format identifier
I/O status specifier
Record number
Error specifier (statement label)
List of variables
Name of the namelist
group
The options can be specified in any order.
An alternate for the
REC=
rn form is allowed, as follows: ♦
WRITE(
u
'
rn
… )
iolist
♦
See Example 3, later on in this section.
Description
For tapes, we recommend the
TOPEN()
routines because they are more reliable.
Unit Identifier
u
is either an external unit identifier or an internal file identifier.
An external unit identifier must be one of the following:
•
A nonnegative integer expression
•
An asterisk, identifying stdout
, which is normally connected to the console
If the optional characters
UNIT=
are omitted from the unit specifier, then u must be the first item in the list of specifiers.
Statements
245
4
246
Format Identifier
f is a format identifier and can be:
•
An asterisk (
*
), indicating list-directed I/O. See “List-Directed I/O” on page
301 for details.
•
The label of a
FORMAT
statement that appears in the same program unit
•
An integer variable name that has been assigned the label of a
FORMAT statement that appears in the same program unit
•
A character expression or integer array that specifies the format string. This is called a runtime format or a variable format. The integer array is nonstandard. ♦
If the optional characters,
FMT=
, are omitted from the format specifier, then f must appear as the second argument for a formatted write; otherwise, it must not appear at all.
f must not be an asterisk for direct access.
f can be an asterisk for internal files. ♦
If a file is connected for formatted I/O, unformatted data transfer is prohibited, and vice versa.
I/O Status Specifier
ios must be an integer variable, integer array element, or integer record field.
Record Number
rn must be a positive integer expression. This argument can appear only for direct-access files. rn can be specified for internal files. ♦
Error Specifier
s must be the label of an executable statement in the same program unit in which this
WRITE
statement occurs.
FORTRAN 77 Reference Manual
4
Output List
iolist can be empty, or it can contain output items or implied
DO
lists. The output items must be one of the following:
•
Variables
•
Substrings
•
Arrays
•
Array elements
•
Record fields
•
Any other expression
A simple unsubscripted array name specifies all of the elements of the array in memory storage order, with the leftmost subscript increasing more rapidly.
If the output item is a character expression that employs the concatenation operator, the length specifiers of its operands can be an asterisk (
*
). This rule is nonstandard. ♦
If a function appears in the output list, that function must not cause an input/output statement to be executed.
Namelist-Directed
WRITE
The second form of
WRITE
is used to output the items of the specified namelist group. Here, grname is the name of the list previously defined in a
NAMELIST statement.
Execution
Execution proceeds as follows:
1. The file associated with the specified unit is determined.
The format, if specified, is established. The file is positioned appropriately prior to data transfer.
2. If the output list is not empty, data is transferred from the list to the file.
Data is edited according to the format, if specified.
3. In the second form of namelist-directed
WRITE
, the data is transferred from the items of the specified namelist group according to the rules of namelist-directed output.
Statements
247
4
4. The file is repositioned appropriately after the data transfer.
5. If ios is specified, and no error occurs, it is set to zero; otherwise, it is set to a positive value.
6. If
s is specified and an error occurs, control is transferred to s.
Restrictions
Note these restrictions:
•
Output from an exception handler is unpredictable.
If you make your own exception handler, do not do any FORTRAN 77 output from it. If you must do some, then call abort right after the output.
Doing so reduces the relative risk of a system freeze. FORTRAN 77 I/O from an exception handler amounts to recursive I/O. See the next paragraph.
•
Recursive I/O does not work reliably.
If you list a function in an I/O list, and if that function does I/O, then during runtime, the execution may freeze, or some other unpredictable problem results. This risk exists independent of using parallelization.
Example: Recursive I/O fails intermittently:
WRITE(*,*) x, f(x) !
Not allowed,
f()
does I/O.
END
FUNCTION F(X)
WRITE(*,*) X
RETURN
END
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4
Comments
If u
specifies an external unit that is not connected to a file, an implicit
OPEN operation is performed that is equivalent to opening the file with the following options:
&
OPEN(
u
,
FILE='FORT.
u
'
, STATUS='UNKNOWN',
ACCESS='SEQUENTIAL', FORM=
fmt
)
The value of fmt is
'FORMATTED'
if the write is formatted, and
'UNFORMATTED'
otherwise.
A simple unsubscripted array name specifies all of the elements of the array in memory storage order, with the leftmost subscript increasing more rapidly.
The record number for direct-access files starts from one onwards.
Namelist-directed output is permitted on sequential access files only.
Examples
Example 1: Formatted write with trap I/O errors and I/O status:
WRITE( 1, 2, ERR=8, IOSTAT=N ) X, Y
RETURN
…
8 WRITE( *, * ) 'I/O error # ', N, ', on 1'
STOP
END
Example 2: Direct, unformatted write, trap I/O errors, and I/O status:
…
WRITE( 1, REC=3, IOSTAT=N, ERR=8 ) V
…
4 CONTINUE
RETURN
8 WRITE( *, * ) 'I/O error # ', N, ', on 1'
END
Statements
249
4
250
Example 3: Direct, alternate syntax (equivalent to above example):
…
WRITE( 1 ' 3, IOSTAT=N, ERR=8 ) V
…
CONTINUE 4
RETURN
8 WRITE( *, * ) 'I/O error # ', N, ', on 1'
END
Example 4: List-directed write to screen: or
WRITE( *, * ) A, V
PRINT *, A, V
Example 5: Formatted write to an internal file:
1
CHARACTER CA*16, L*8 /'abcdefgh'/, R*8 /'ijklmnop'/
WRITE( CA, 1 ) L, R
FORMAT( 2 A8 )
Example 6: Write an entire array:
DIMENSION V(5)
WRITE( 3, '(5F4.1)') V
Example 7: Namelist-directed write:.
CHARACTER SAMPLE*16
LOGICAL NEW*4
REAL DELTA*4
NAMELIST /G/ SAMPLE, NEW, DELTA
…
WRITE( 1, G ) or or
WRITE( UNIT=1, NML=G )
WRITE( 1, NML=G )
FORTRAN 77 Reference Manual
Input and Output
5
This chapter describes the general concepts of FORTRAN 77 input and output, and provides details on the different kids of I/O. It is organized into the following sections:
General Concepts of FORTRAN 77 I/O
Direct Access
Internal Files
Formatted I/O
Unformatted I/O
List-Directed I/O
NAMELIST I/O page 251 page 259 page 260 page 261 page 298 page 301 page 305
5.1 General Concepts of FORTRAN 77 I/O
Any operating system based on the UNIX operating system is not as recordoriented as FORTRAN 77. This operating system treats files as sequences of characters instead of collections of records. The FORTRAN 77 runtime system keeps track of file formats and access mode during runtimes. It also provides the file facilities, including the FORTRAN 77 libraries and the standard I/O library.
251
5
252
Logical Units
The FORTRAN 77 default value for the maximum number of logical units that a program can have open at one time is 64. For current Solaris releases, this limit is 256. A FORTRAN 77 program can increase this limit beyond 64 by calling the setrlim()
function. See the man
page setrlim
(2). If you are running csh
, you can also do this with the limit
or unlimit
command; see csh
(1).
The standard logical units 0, 5, and 6 are preconnected to Solaris as stderr
, stdin
, and stdout
, respectively. These are not actual file names, and cannot be used for opening these units.
INQUIRE
does not return these names, and indicates that the above units are not named unless they have been opened to real files. However, these units can be redefined with an
OPEN
statement.
The names, stderr
, stdin
, and stdout
, are meant to make error reporting more meaningful. To preserve error reporting, the system makes it is an error to close logical unit 0, although it can be reopened to another file.
If you want to open a file with the default file name for any preconnected logical unit, remember to close the unit first. Redefining the standard units can impair normal console I/O. An alternative is to use shell redirection to externally redefine the above units.
To redefine default blank control or the format of the standard input or output files, use the
OPEN
statement, specifying the unit number and no file name, and use the options for the kind of blank control you want.
I/O Errors
Any error detected during I/O processing causes the program to abort, unless alternative action has been provided specifically in the program. Any I/O statement can include an
ERR=
clause (and
IOSTAT=
clause) to specify an alternative branch to be taken on errors and return the specific error code.
Read statements can include
END=
n to branch on end-of-file. File position and the value of I/O list items are undefined following an error.
END=
catches both
EOF and error conditions;
ERR=
catches only error conditions.
If your program does not trap I/O errors, then before aborting, an error message is written to stderr
with an error number in square brackets,
[ ]
, and the logical unit and I/O state. The signal that causes the abort is
IOT
.
FORTRAN 77 Reference Manual
5
Error numbers less than 1000 refer to operating system errors; see intro
(2).
Error numbers greater than or equal to 1000 come from the I/O library.
For external I/O, part of the current record is displayed if the error was caused during reading from a file that can backspace. For internal I/O, part of the string is printed with a vertical bar (
|
) at the current position in the string.
General Restriction
Do not reference a function in an I/O list if executing that function causes an
I/O statement to be executed. Example:
WRITE( 1, 10) Y, A + 2.0 * F(X)
! Wrong if
F()
does I/O
Kinds of I/O
The four kinds of I/O are: formatted, unformatted, list-directed, and
NAMELIST
.
The two modes of access to files are sequential and direct. When you open a file, the access mode is set to either sequential or direct. If you do not set it explicitly, you get sequential by default.
The two types of files are: external files and internal files. An external file resides on a physical peripheral device, such as disk or tape. An internal file is a location in main memory, is of character type, and is either a variable, substring, array, array element, or a field of a structured record.
Combinations of I/O
I/O combinations on external files are:
Allowed
Sequential unformatted
Sequential formatted
Sequential list-directed
Sequential
NAMELIST
Direct unformatted
Direct formatted
Not Allowed
Direct-access, list-directed I/O
Direct-access,
NAMELIST
I/O
NAMELIST
I/O on internal files
Unformatted, internal I/O
Input and Output
253
5
The following table shows combinations of I/O form, access mode, and physical file types.
NAMELIST
External
Internal
External
Table 5-1
Summary of f77
Input and Output
Kind of I/O
Form
Formatted
File Type
Internal
External
Unformatted Internal
External
List-directed Internal
Access Mode
Sequential
The file is a character variable, substring, array, or array element.
♦
Only formatted records of same or variable length.
Not allowed.
Contains only unformatted records.
READ
: Reads characters until EOF or I/O list is satisfied.
Direct
The file is a character array; each record is one array element.
Only formatted records, all the same length.
Not allowed.
READ
: Gets one logical record at a time.
WRITE
: Unfilled part of record is undefined.
Not allowed.
WRITE
: Writes records until list is satisfied.
♦
Uses standard formats based on type of variable and size of element. Blanks or commas are separators. Any columns.
Not allowed.
READ
: Reads records until it finds
$
groupname in columns
2-80. Then reads records searching for names in that group, and stores data in those variables. Stops reading on
$
or eof
.
Not allowed.
Not allowed.
Not allowed.
WRITE
: Writes records showing the group name and each variable name with value.
Avoid list-directed internal writes. The number of lines and items per line varies with the values of items.
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5
Printing Files
You get a print file by using the nonstandard
FORM
=
'PRINT'
in
OPEN
. ♦
OPEN ( ..., FORM='PRINT', ... )
This specifier works for sequential access files only.
Definition
A print file has the following features:
•
With formatted output, you get vertical format control for that logical unit:
•
Column one is not printed.
•
If column one is blank, 0, or 1, then vertical spacing is one line, two lines, or top of page, respectively.
•
If column 1 is
+
, it is replaced by a control sequence that causes a return to the beginning of the previous line.
•
With list-directed output, you get for that logical unit, column one is not printed.
In general, if you open a file with
FORM
=
'PRINT'
, then for that file listdirected output does not provide the FORTRAN 77 Standard blank in column one; otherwise, it does provide that blank.
FORM
=
'PRINT'
is for one file per call.
If you open a file with
FORM='PRINT'
, then that file has the same content as if it was opened with
FORM='FORMATTED'
, and filtered with the output filter, asa
.
If you compile with the
-oldldo
option (old list-directed output), then all the files written by the program do list-directed output without that blank in column one; otherwise, they all get that blank. The
-oldldo
option is global.
The
INQUIRE
Statement
The
INQUIRE
statement returns '
PRINT'
in the
FORM
variable for logical units opened as print files. It returns
-1
for the unit number of an unopened file.
Input and Output
255
5
256
Special Uses of
OPEN
If a logical unit is already open, an
OPEN
statement using the
BLANK
option does nothing but redefine that option.
As a nonstandard extension, if a logical unit is already open, an
OPEN statement using the
FORM
option does nothing but redefine that option. ♦
These forms of the
OPEN
statement need not include the file name, and must not include a file name if
UNIT
refers to standard input, output, or standard error.
If you connect a unit with
OPEN
and do not use the file name parameter, then you get the default file name, fort.
nn, where nn is the unit number.
Therefore, to redefine the standard output as a print file, use:
OPEN( UNIT=6, FORM='PRINT')
Scratch Files
Scratch files are temporary files that normally disappears after execution is completed.
Example: Create a scratch file:
OPEN( UNIT=7, STATUS='SCRATCH' )
To prevent a temporary file from disappearing after execution is completed, you must execute a
CLOSE
statement with
STATUS='KEEP'
.
KEEP
is the default status for all other files.
Example: Close a scratch file that you want to access later:
CLOSE( UNIT=7, STATUS='KEEP' )
Remember to get the real name of the scratch file. Use
INQUIRE
if you want to reopen it later.
FORTRAN 77 Reference Manual
5
Changing I/O Initialization with
IOINIT
Traditional FORTRAN 77 environments usually assume carriage control on all logical units. They usually interpret blank spaces on input as zeroes, and often provide attachment of global file names to logical units at runtime. The routine
IOINIT
(3F) can be called to specify these I/O control parameters. This routine:
•
Recognizes carriage control for all formatted files.
•
Ignores trailing and embedded blanks in input files.
•
Positions files at the beginning or end upon opening.
•
Preattaches file names of a specified pattern with logical units.
Example:
IOINIT
and logical unit preattachment:
CALL IOINIT ( .TRUE., .FALSE., .FALSE., 'FORT', .FALSE.)
For the above call, the FORTRAN 77 runtime system looks in the environment for names of the form
FORT
nn, and then opens the corresponding logical unit for sequential formatted I/O.
With the above example, suppose your program opened unit 7, as follows:
OPEN( UNIT=07, FORM='FORMATTED' )
The FORTRAN 77 runtime system looks in the environment for the
FORT07 file, and connects it to unit 7.
In general, names must be of the form PREFIXnn, where the particular PREFIX is specified in the call to
IOINIT
, and nn is the logical unit to be opened. Unit numbers less than 10 must include the leading 0. For details, see
IOINIT
(3F).
Example: Attach external files ini1.inp
and ini1.out
to units 1and 2:
In sh
: demo$ TST01=ini1.inp demo$ TST02=ini1.out demo$ export TST01 TST02
Input and Output
257
5
258
In csh
: demo% setenv TST01 ini1.inp demo% setenv TST02 ini1.out
Example: Attach the file, s ini1.inp
and ini1.out
, to units 1 and 2:
&
C demo% cat ini1.f
CHARACTER PRFX*8
LOGICAL CCTL, BZRO, APND, VRBOSE
DATA CCTL, BZRO, APND, PRFX, VRBOSE
/.TRUE., .FALSE., .FALSE., 'TST', .FALSE. /
CALL IOINIT( CCTL, BZRO, APND, PRFX, VRBOSE )
READ( 1, *) I, B, N
WRITE( *, *) 'I = ', I, ' B = ', B, ' N = ', N
WRITE( 2, *) I, B, N
END demo% f77 ini1.f ini1.f:
MAIN: demo% a.out
I = 12 B = 3.14159012 N = 6 demo%
IOINIT
should prove adequate for most programs as written. However, it is written in FORTRAN 77 so that it can serve as an example for similar usersupplied routines. A copy can be retrieved as follows:
In Solaris 2.x: demo% cp /opt/SUNWspro/SC3.0.1/src/ioinit.f .
In Solaris 1.x: demo% cp /usr/lang/SC3.0.1/src/ioinit.f .
FORTRAN 77 Reference Manual
5
5.2 Direct Access
A direct-access file contains a number of records that are written to or read from by referring to the record number. Direct access is also called random access.
In direct access:
•
Records must be all the same length.
•
Records are usually all the same type.
•
A logical record in a direct access, external file is a string of bytes of a length specified when the file is opened.
•
Read and write statements must not specify logical records longer than the original record size definition.
•
Shorter logical records are allowed.
•
Unformatted direct writes leave the unfilled part of the record undefined.
•
Formatted direct writes pass the unfilled record with blanks.
•
Each
READ
operation acts on exactly one record.
•
In using direct unformatted I/O, be careful with the number of values your program expects to read.
•
Direct access
READ
and
WRITE
statements have an argument,
REC=
n, which gives the record number to be read or written. An alternate, nonstandard form is
'
n.
Unformatted I/O
Example: Direct access, unformatted:
&
OPEN( 2, FILE='data.db', ACCESS='DIRECT', RECL=20,
FORM='UNFORMATTED', ERR=90 )
READ( 2, REC=13, ERR=30 ) X, Y
READ( 2 ' 13, ERR=30 ) X, Y !
←
Alternate form
♦
This code opens a file for direct-access, unformatted I/O, with a record length of 20 characters, then reads the thirteenth record as is.
Input and Output
259
260
5
Formatted I/O
Example: Direct access, formatted:
&
OPEN( 2, FILE='inven.db', ACCESS='DIRECT', RECL=20,
FORM='FORMATTED', ERR=90 )
READ( 2, FMT='(I10,F10.3)', REC=13, ERR=30 ) A, B
This code opens a file for direct-access, formatted I/O, with a record length of
20 characters, then reads the thirteenth record and converts it according to the
(I10,F10.3)
format.
5.3 Internal Files
An internal file is a character-string object, such as a constant, variable, substring, array, element of an array, or field of a structured record—all of type character. For a variable or substring, there is only a single record in the file but for an array; each array element is a record.
Sequential Formatted I/O
On internal files, the FORTRAN 77 Standard includes only sequential formatted I/O. (I/O is not a precise term to use here, but internal files are dealt with using
READ
and
WRITE
statements.) Internal files are used by giving the name of the character object in place of the unit number. The first read from a sequential-access internal file always starts at the beginning of the internal file; similarly for a write.
Example: Sequential, formatted reads:
CHARACTER X*80
READ( 5, '(A)' ) X
READ( X, '(I3,I4)' ) N1, N2
The above code reads a print-line image into
X
, and then reads two integers from
X
.
FORTRAN 77 Reference Manual
5
Direct Access I/O
f77
extends direct I/O to internal files.♦
This is like direct I/O on external files, except that the number of records in the file cannot be changed. In this case, a record is a single element of an array of character strings.
Example: Direct access read of the third record of the internal file,
LINE
: demo% cat intern.f
CHARACTER LINE(3)*14
DATA LINE(1) / ' 81 81 ' /
DATA LINE(2) / ' 82 82 ' /
DATA LINE(3) / ' 83 83 ' /
READ ( LINE, FMT='(2I4)', REC=3 ) M, N
PRINT *, M, N
END demo% f77 -silent intern.f demo% a.out
83 83 demo%
5.4 Formatted I/O
In formatted I/O:
•
The list items are processed in the order they appear in the list.
•
Any list item is completely processed before the next item is started.
•
Each sequential access reads or writes one or more logical records.
Input Actions
In general, a formatted read statement does the following:
•
Reads character data from the external record or from an internal file.
•
Converts the items of the list from character to binary form according to the instructions in the associated format.
•
Puts converted data into internal storage for each list item of the list.
Input and Output
261
5
Example: Formatted read:
READ( 6, 10 ) A, B
10 FORMAT( F8.3, F6.2 )
Output Actions
In general, a formatted write statement does the following:
•
Gets data from internal storage for each list item specified by the list.
•
Converts the items from binary to character form according to the instructions in the associated format.
•
Transfers the items to the external record or to an internal file.
•
Terminates formatted output records with newline characters.
Example: Formatted write:
REAL A / 1.0 /, B / 9.0 /
WRITE( 6, 10 ) A, B
10 FORMAT( F8.3, F6.2 )
For formatted write statements, the logical record length is determined by the format statement that interacts with the list of input or output variables (I/O list) at execution time.
For formatted write statements, if the external representation of a datum is too large for the field width specified, the specified field is filled with asterisks (
*
).
For formatted read statements, if there are fewer items in the list than there are data fields, the extra fields are ignored.
262
FORTRAN 77 Reference Manual
5
Format Specifiers
Table 5-2
Format Specifiers
Specifiers can be uppercase as well as lowercase characters in format statements and in all the alphabetic arguments to the
I/O library routines.
Purpose
Blank control
Carriage control
Character edit
Floating-point edit
FORTRAN 77
BN, BZ
/,
space,
0
,
1
n
H, A
w,
'aaa'
D
w
.
d
E
e
,
E
w
.
d
E
e
,
F
w
.
d
E
e
,
G
w
.
d
E
e
f77
Extensions
B
$
"aaa"
,
A
E
w
.
d
.
e
,
D
w
.
d
.
e
,
G
w
.
d
.
e
Z
w
.
m
Hexadecimal edit
Integer edit
Logical edit
Octal edit
Position control
Radix control
Remaining characters
Scale control
Sign control
Terminate a format
Variable format expression
I
w.m
L
w n
X
,
T
n,
TL
n,
TR
n
:
n
P
S
,
SP
,
SS
O
w
.
m n
T, T, X
n
R, R
Q
P
SU
< e >
w, m, d, e Parameters (As In
G
w
.
d
E
e)
The definitions for the parameters, w, m, d, and e are:
•
w specifies that the field occupies w positions.
•
m specifies the insertion of leading zeros to a width of m.
•
d specifies the number of digits to the right of the decimal point.
•
e specifies the width of the exponent field.
Input and Output
263
5
Defaults for w, d, and e
You can write field descriptors
A
,
D
,
E
,
F
,
G
,
I
,
L
,
O
, or
Z
without the w, d, or e field indicators. ♦ If these are not unspecified, the appropriate defaults are used based on the data type of the I/O list element. See Table 5-3.
Typical format field descriptor forms that use w, d, or e include:
A
w
, I
w
, L
w
, O w
,
Z
w
, D
w
.
d
, E
w
.
d
, G
w
.
d
, E
w
.
d
E
e
, G
w
.
d
E
e
Example: With the default w=7 for
INTEGER*2
, and since 161 decimal = A1 hex:
INTEGER*2 M
M = 161
WRITE ( *, 8 ) M
8 FORMAT ( Z )
END
This example produces the following output: demo% f77 def1.f def1.f:
MAIN: demo% a.out
∆∆∆∆∆ a1 demo%
↑
column 6
264
FORTRAN 77 Reference Manual
5
The defaults for w, d, and e are summarized in the following table.
A
A
A
Field Descriptor
I,O,Z
I,O,Z
I,O,Z
O,Z
O,Z
O,Z
A
A
A
A
L
F,E,D,G
F,E,D,G
F,E,D,G
Table 5-3
Default w, d, e Values in Format Field Descriptors
List Element
BYTE
INTEGER*2
,
LOGICAL*2
INTEGER*4
,
LOGICAL*4
REAL*4
REAL*8
REAL*16
,
COMPLEX*32
LOGICAL
REAL
,
COMPLEX*8
REAL*8
,
COMPLEX*16
REAL*16
,
COMPLEX*32
LOGICAL*1
LOGICAL*2
,
INTEGER*2
LOGICAL*4
,
INTEGER*4
REAL*4
,
COMPLEX*8
REAL*8
,
COMPLEX*16
REAL*16
,
COMPLEX*32
CHARACTER*n
4
4
1
2
2
15
25
42
8
16 n
12
12
23
44
w
7
7
-
-
-
-
-
7
16
33
-
-
-
-
-
-
-
d
-
-
-
-
-
-
2
3
-
2
-
-
-
-
-
-
-
e
-
-
For complex items, the value for w is for each real component. The default for the
A
descriptor with character data is the declared length of the corresponding
I/O list element.
REAL*16
and
COMPLEX*32
are for SPARC only.
Apostrophe Editing (
'
aaa
'
)
The apostrophe edit specifier is in the form of a character constant. It causes characters to be written from the enclosed characters of the edit specifier itself, including blanks. An apostrophe edit specifier must not be used on input. The width of the field is the number of characters contained in, but not including,
Input and Output
265
5
266 the delimiting apostrophes. Within the field, two consecutive apostrophes with no intervening blanks are counted as a single apostrophe. You can use quotes in a similar way.
Example: apos.f
, apostrophe edit (two equivalent ways):
WRITE( *, 1 )
1 FORMAT( 'This is an apostrophe ''.')
WRITE( *, 2 )
2 FORMAT( "This is an apostrophe '.")
END
The above program writes this message twice:
This is an apostrophe '.
Blank Editing (B
,
BN
,
BZ)
The
B
,
BN
, and
BZ
edit specifiers control interpretation of imbedded and trailing blanks for numeric input.
The following blank specifiers are available:
•
BN
—If
BN
precedes a specification, a nonleading blank in the input data is considered null, and is ignored.
•
BZ
—If
BZ
precedes a specification, a nonleading blank in the input data is considered zero.
•
B
—If
B
precedes a specification, it returns interpretation to the default mode of blank interpretation. This is consistent with
S
, which returns to the default sign control. ♦
Without any specific blank specifiers in the format, nonleading blanks in numeric input fields are normally interpreted as zeros or ignored, depending on the value of the
BLANK=
suboption of
OPEN
currently in effect for the unit.
The default value for that suboption is ignore
, so if you use defaults for both
BN/BZ/B
and
BLANK=
, you get ignore
.
FORTRAN 77 Reference Manual
5
Example: Read and print the same data once with
BZ
and once with
BN
: demo% cat bz1.f
* 12341234
CHARACTER LINE*18 / ' 82 82 ' /
READ ( LINE, '( I4, BZ, I4 ) ') M, N
PRINT *, M, N
READ ( LINE, '( I4, BN, I4 ) ') M, N
PRINT *, M, N
END demo% f77 -silent bz1.f demo% a.out
82 8200
82 82 demo%
Note these rules for blank control:
•
Blank control specifiers apply to input only.
•
A blank control specifier remains in effect until another blank control specifier is encountered, or format interpretation is complete.
•
The
B
,
BN
, and
BZ
specifiers affect only
I
,
F
,
E
,
D
, and
G
editing.
Carriage Control (
$
, Space,
0,1
)
You use
$
, the space,
0
, and
1
for carriage control.
Dollar
$
The special edit descriptor
$
suppresses the carriage return. ♦
The action does not depend on the first character of the format. It is used typically for console prompts. For instance, you can use this descriptor to make a typed response follow the output prompt on the same line. This edit descriptor is constrained by the same rules as the colon (
:
).
Input and Output
267
5
268
Example: The
$
carriage control:
* dol1.f The $ edit descriptor with space
WRITE ( *, 2 )
2 FORMAT (' Enter the node number: ', $ )
READ ( *, * ) NODENUM
END
The above code produces a displayed prompt and user input response, such as:
Enter the node number: 82
The first character of the format is printed out, in this case, a blank. For an input statement, the
$
descriptor is ignored.
Space,0
,
1
,
and
+
The following first-character slew controls and actions are provided:
Table 5-4
Carriage Control with Blank,
0
,
1
, and
+
Character
1
+
Blank
0
Vertical spacing before printing
One line
Two lines
To first line of next page
No advance ( stdout
only, not files)
If the first character of the format is not space,
0
,
1
, or +, then it is treated as a space, and it is not printed.
The behavior of the slew control character
+
is: if the character in the first column is
+
, it is replaced by a control sequence that causes printing to return to the first column of the previous line, where the rest of the input line is printed.
Space,
0
,
1
, and
+
work for stdout
if piped through asa
.
FORTRAN 77 Reference Manual
Printer
Screen
5
Example: First-character formatting, standard output piped through asa
: demo% cat slew1.f
WRITE( *, '("abcd")')
WRITE( *, '(" efg")') !
The blank single spaces
WRITE( *, '("0hij")') !
The "0" double spaces
WRITE( *, '("1klm")') !
The "1" starts this on a new page
WRITE( *, '("+", T5, "nop")') !
The "+" starts this at col 1 of latest line
END demo% f77 -silent slew1.f demo% a.out | asa | lpr demo%
The program, slew1.f
produces file, slew1.out
, as printed by lpr
: bcd efg hij klmnop
←
This starts on a new page. The
+
of
+nop
is obeyed.
The results are different on a screen; the tabbing puts in spaces: demo% cat slew1.out bcd efg hij
nop demo%
←
This starts on a new page. The
+
of
+nop
is obeyed.
See asa
(1).
The space,
0
, and
1
, and
+
work for a file opened with:
•
Sequential access
•
FORM='PRINT'
Input and Output
269
5
270
Example: First-character formatting, file output: demo% cat slew2.f
OPEN( 1,FILE='slew.out',FORM='PRINT' )
WRITE( 1, '("abcd")')
WRITE( 1, '("efg")')
WRITE( 1, '("0hij")')
WRITE( 1, '("1klm")')
WRITE( 1, '("+", T5, "nop")')
CLOSE( 1, STATUS='KEEP')
END demo% f77 -silent slew2.f demo% a.out
The program, slew2.f
, produces the file, slew2.out
, that is equal to the file, slew1.out
, in the example above.
Slew control codes
'0'
,
'1'
, and
'+'
in column one are in the output file as
'\n'
,
'\f'
, and
'\r'
, respectively.
Character Editing (
A
)
The
A
specifier is used for character type data items. The general form is:
A [
w
]
On input, character data is stored in the corresponding list item.
On output, the corresponding list item is displayed as character data.
If w is omitted, then:
•
For character data type variables, it assumes the size of the variable.
•
For noncharacter data type variables, it assumes the maximum number of characters that fit in a variable of that data type. This is nonstandard behavior.
♦
FORTRAN 77 Reference Manual
5
Each of the following examples read into a size n variable (
CHARACTER*
n), for various values of n, for instance, for n = 9.
CHARACTER C*9
READ '( A7 )', C
The various values of n, in
CHARACTER C*
n are:
Size
n
Data
Format
Memory
9
Node
∆
Id
A7
Node
∆
Id
∆∆
7
Node
∆
Id
A7
Node
∆
Id
4
Node
∆
Id
A7
e
∆
Id
1
Node
∆
Id
A7
d
∆
indicates a blank space.
Example: Output strings of 3, 5, and 7 characters, each in a 5 character field:
PRINT 1, 'The', 'whole', 'shebang'
1 FORMAT( A5 / A5 / A5 )
END
The above program displays:
∆∆
The whole sheba
Input and Output
271
5
272
The maximum characters in noncharacter types are summarized in the following table.
Table 5-5
Maximum Characters in Noncharacter Type Hollerith (nHaaa)
Type of List Item
BYTE
LOGICAL*1
LOGICAL*2
LOGICAL*4
LOGICAL*8
INTEGER*2
INTEGER*4
INTEGER*8
REAL
REAL*4
REAL*8
REAL*16
(SPARC only)
DOUBLE PRECISION
COMPLEX
COMPLEX*8
COMPLEX*16
COMPLEX*32
(SPARC only)
DOUBLE COMPLEX
Maximum Number of Characters
1
1
2
4
8
2
4
8
4
4
8
16
8
8
8
16
32
16
In f77
, you can use Hollerith constants wherever a character constant can be used in
FORMAT
statements, assignment statements, and
DATA
statements.♦
These constants are not recommended. FORTRAN 77 does not have these old
Hollerith (n
H
) notations, although the FORTRAN 77 Standard recommends implementing the Hollerith feature to improve compatibility with old programs. But such constants cannot be used as input data elements in listdirected or
NAMELIST
input.
For example, these two formats are equivalent:
10 FORMAT( 8H Code = , A6 )
20 FORMAT( ' Code = ', A6 )
FORTRAN 77 Reference Manual
5
In f77
, commas between edit descriptors are generally optional:
10 FORMAT( 5H flex 4Hible )
READ
s into Hollerith Edit Descriptors
For compatibility with older programs, f77
also allows
READ s into Hollerith edit descriptors. ♦
Example: Read into hollerith edit descriptor—no list in the
READ
statement: demo% cat hol1.f
WRITE( *, 1 )
1 FORMAT( 6Holder )
READ( *, 1 )
WRITE( *, 1 )
END demo% f77 hol1.f hol1.f:
MAIN demo% a.out older
newer
newer demo%
In the above code, if the format is a runtime format (variable format), then the reading into the actual format does not work, and the format remains unchanged. Hence, the following program fails:
CHARACTER F*18 / '(A8)' /
READ(*,F) !
←
Does not work.
…
Obviously, there are better ways to read into the actual format.
Input and Output
273
5
274
Integer Editing (
I
)
The
I
specifier is used for decimal integer data items. The general form is:
I [
w
[ .
m
] ]
The
I
w and
I
w.m edit specifiers indicate that the field to be edited occupies w positions. The specified input/output list item must be of type integer. On input, the specified list item becomes defined with an integer datum. On output, the specified list item must be defined as an integer datum.
On input, an
I
w.m edit specifier is treated identically to an
I
w edit specifier.
The output field for the
I
w edit specifier consists of:
•
Zero or more leading blanks followed by
•
Either a minus if the value is negative, or an optional plus, followed by
•
The magnitude of the value in the form on an unsigned integer constant without leading zeros
An integer constant always has at least one digit.
The output field for the
I
w.m edit specifier is the same as for the
I
w edit specifier, except that the unsigned integer constant consists of at least m digits, and, if necessary, has leading zeros. The value of m must not exceed the value of w. If m is zero, and the value of the item is zero, the output field consists of only blank characters, regardless of the sign control in effect.
Example: int1.f
, integer input:
CHARACTER LINE*8 / '12345678' /
READ( LINE, '(I2, I3, I2 )') I, J, K
PRINT *, I, J, K
END
The program above displays:
12 345 67
FORTRAN 77 Reference Manual
5
Example: int2.f
, integer output:
N = 1234
PRINT 1, N, N, N, N
1 FORMAT( I6 / I4 / I2 / I6.5 )
END
The above program displays:
1234
1234
**
01234
Logical Editing (
L
)
The
L
specifier is used for logical data items. The general form is:
L
w
The
L
w edit specifier indicates that the field occupies w positions. The specified input/output list item must be of type
LOGICAL
. On input, the list item becomes defined with a logical datum. On output, the specified list item must be defined as a logical datum.
The input field consists of optional blanks, optionally followed by a decimal point, followed by a
T
for true, or
F
for false. The
T
or
F
can be followed by additional characters in the field. The logical constants,
.TRUE.
and
.FALSE., are acceptable as input. The output field consists of w-1 blanks followed by a
T
for true, or
F
for false.
Example: log1.f
, logical output:
LOGICAL A*1 /.TRUE./, B*2 /.TRUE./, C*4 /.FALSE./
PRINT '( L1 / L2 / L4 )', A, B, C
END
Input and Output
275
5
276
The program above displays:
T
∆
T
∆∆∆
F
Example: log2.f
, logical input:
LOGICAL*4 A
1 READ '(L8)', A
PRINT *, A
GO TO 1
END
The program above accepts any of the following as valid input data: t true T TRUE .t .t. .T .T. .TRUE. TooTrue f false F FALSE .f .F .F. .FALSE. Flakey
Octal and Hexadecimal Editing (
O
,
Z
)
The
O
and
Z
field descriptors for a
FORMAT
statement are for octal and hexadecimal integers, respectively, but they can be used with any data type.♦
The general form is:
O
w
[.
m
]
Z
w
[.
m
] where w is the number of characters in the external field. For output, m, if specified, determines the total number of digits in the external field; that is, if there are fewer than m nonzero digits, the field is zero-filled on the left to a total of m digits. m has no effect on input.
FORTRAN 77 Reference Manual
5
Octal and Hex Input
A
READ
, with the
O
or
Z
field descriptors in the
FORMAT
, reads in w characters as octal or hexadecimal, respectively, and assigns the value to the corresponding member of the I/O list.
Example: Octal input, the external data field is:
654321
↑
column 1
The program that does the input is:
READ ( *, 2 ) M
2 FORMAT ( O6 )
The above data and program result in the octal value 654321 being loaded into the variable
M
. Further examples are included in the following table.
Table 5-6
Sample Octal/Hex Input Values
Format
O4
O4
O3
Z5
Z5
Z4
External Field
1234
∆
16234
97
∆∆∆
A23DE
∆
A23DEF
95.AF2
Internal (Octal or Hex) Value
1234
1623
Error: “9” not allowed
A23DE
A23DE
Error: “.” not allowed
The general rules for octal and hex input are:
•
For octal values, the external field can contain only numerals 0 through 7.
•
For hexadecimal values, the external field can contain only numerals 0 through 9 and the letters
A
through
F
or a
through f
.
•
Signs, decimal points, and exponent fields are not allowed.
•
All-blank fields are treated as having a value of zero.
•
If a data item is too big for the corresponding variable, an error message is displayed.
Input and Output
277
5
278
Octal and Hex Output
A
WRITE
, with the
O
or
Z
field descriptors in the
FORMAT
, writes out values as octal or hexadecimal integers, respectively. It writes to a field that is w characters wide, right-justified.
Example: Hex output:
M = 161
WRITE ( *, 8 ) M
8 FORMAT ( Z3 )
END
The program above displays
A1
(161 decimal = A1 hex):
∆
A1
↑
column 2
Further examples are included in the following table.
Format
O6
O2
O4.3
O4.4
O6
Z4
Z3.3
Z6.4
Z5
Table 5-7
Sample Octal/Hex Output Value
Internal (Decimal) Value
32767
14251
27
27
-32767
32767
2708
2708
-32767
External (Octal/Hex) Representation
∆
77777
**
∆
033
0033
100001
7FFF
A94
∆∆
0A94
∆
8001
The general rules for octal and hex output are:
•
Negative values are written as if unsigned; no negative sign is printed.
•
The external field is filled with leading spaces, as needed, up to the width w.
•
If the field is too narrow, it is filled with asterisks.
•
If m is specified, the field is left-filled with leading zeros, to a width of m.
FORTRAN 77 Reference Manual
5
Positional Editing (
T
, n
T
,
TR
n,
TL
n, n
X
)
For horizontal positioning along the print line, f77
supports the forms:
TR
n,
TL
n,
T
n, n
T
,
T where n is a strictly positive integer. The format specifier
T
can appear by itself, or be preceded or followed by a positive nonzero number.
T
n—Absolute Columns
This tab reads from the nth column or writes to the nth column.
TL
n—Relative Columns
This tab reads from the nth column to the left or writes to the nth column to the
left.
TR
n—Relative Columns
This tab reads from the nth column to the right or writes to the nth column to the right.
n
TL
—Relative Tab Stop
This tab tabs to the nth tab stop for both read and write. If n is omitted, this tab uses n = 1 and tabs to the next tab stop.
TL
—Relative Tab Stop
This tab tabs to the next tab stop for both read and write. It is the same as the
n
TL
with n omitted; it tabs to the next tab stop.
The rules and Restrictions for tabbing are:
•
Tabbing right beyond the end of an input logical record is an error.
•
Tabbing left beyond the beginning of an input logical record leaves the input pointer at the beginning of the record.
•
Nondestructive tabbing is implemented for both internal and external formatted I/O. Nondestructive tabbing means that tabbing left or right on output does not destroy previously written portions of a record.
Input and Output
279
5
280
•
Tabbing right on output causes unwritten portions of a record to be filled with blanks.
•
Tabbing left requires that the logical unit allows a seek
. Therefore, it is not allowed in I/O to or from a terminal or pipe.
•
Likewise, nondestructive tabbing in either direction is possible only on a unit that can seek. Otherwise, tabbing right or spacing with the
X
edit specifier writes blanks on the output.
•
Tab stops are hard-coded every eight columns.
n
X
—Positions
The n
X
edit specifier indicates that the transmission of the next character to or from a record is to occur at the position n characters forward from the current position.
On input, the n
X
edit specifier advances the record pointer by n positions, skipping n characters.
A position beyond the last character of the record can be specified if no characters are transmitted from such positions.
On output, the n
X
specifier writes n blanks.
The n defaults to 1.
Example: Input,
T
n (absolute tabs): demo% cat rtab.f
CHARACTER C*2, S*2
OPEN( 1, FILE='mytab.data')
2
DO I = 1, 2
READ( 1, 2 ) C, S
FORMAT( T5, A2, T1, A2 )
PRINT *, C, S
END DO
END demo%
FORTRAN 77 Reference Manual
The two-line data file is: demo% cat mytab.data defguvwx
12345678 demo%
The run and the output are: demo% a.out
uvde
5612 demo%
The above example first reads columns 5 and 6, then columns 1 and 2.
Example: Output
T
n (absolute tabs); this program writes an output file: demo% cat otab.f
CHARACTER C*20 / "12345678901234567890" /
OPEN( 1, FILE=’mytab.rep’)
WRITE( 1, 2 ) C, ":", ":"
2 FORMAT( A20, T10, A1, T20, A1 )
END demo%
The output file is: demo% cat mytab.rep
123456789:123456789: demo%
The above example writes 20 characters, then changes columns 10 and 20.
5
Input and Output
281
5
Example: Input,
TR
n and
TL
n (relative tabs)—the program reads: demo% cat rtabi.f
CHARACTER C, S, T
OPEN( 1, FILE='mytab.data')
DO I = 1, 2
READ( 1, 2 ) C, S, T
2
END DO
END demo%
FORMAT( A1, TR5, A1, TL4, A1 )
PRINT *, C, S, T
The two-line data file is: demo% cat mytab.data defguvwx
12345678 demo%
The run and the output are: demo% a.out dwg
174 demo%
The above example reads column 1, then tabs right 5 to column 7, then tabs left
4 to column 4.
282
FORTRAN 77 Reference Manual
5
Example: Output
TR
n and
TL
n (relative tabs)—this program writes an output file: demo% cat rtabo.f
CHARACTER C*20 / "12345678901234567890" /
OPEN( 1, FILE='rtabo.rep')
WRITE( 1, 2 ) C, ":", ":"
2 FORMAT( A20, TL11, A1, TR9, A1 )
END demo%
The run shows nothing, but you can list the mytab.rep
output file: demo% cat rtabo.rep
123456789:123456789: demo%
The above program writes 20 characters, tabs left 11 to column 10, then tabs right 9 to column 20.
Quotes Editing (
"aaa"
)
The quotes edit specifier is in the form of a character constant.♦ It causes characters to be written from the enclosed characters of the edit specifier itself, including blanks. A quotes edit specifier must not be used on input.
The width of the field is the number of characters contained in, but not including, the delimiting quotes. Within the field, two consecutive quotes with no intervening blanks are counted as a single quote. You can use apostrophes in a similar way.
Example: quote.f ( two equivalent ways):
WRITE( *, 1 )
1 FORMAT( 'This is a quote ".' )
WRITE( *, 2 )
2 FORMAT( "This is a quote ""." )
END
Input and Output
283
284
5
SU
is described in the section,
“Sign Editing (SU, SP, SS, S)."
This program writes this message twice:
This is a quote ".
Radix Control (
R
)
The format specifier is
R
or n
R
, where 2
≤
n
≤
36. ♦ If n is omitted, the default decimal radix is restored.
You can specify radixes other than 10 for formatted integer I/O conversion.
The specifier is patterned after
P
, the scale factor for floating-point conversion.
It remains in effect until another radix is specified or format interpretation is complete. The I/O item is treated as a 32-bit integer.
Example: Radix 16—the format for an unsigned, hex, integer, 10 places wide, zero-filled to 8 digits, is
(su, 16r, I10.8)
, as in: demo% cat radix.f integer i / 110 / write( *, 1 ) i
1 format( su, 16r, I10.8 ) end demo% f77 -silent radix.f demo% a.out
∆∆
0000006e demo%
Real Editing (
D
,
E
,
F
,
G
)
The
D
,
E
,
F
, and
G
specifiers are for decimal real data items.
D Editing
The
D
specifier is for the exponential form of decimal double-precision items.
The general form is:
D [
w
[ .
d
] ]
The
D
w and
D
w.d edit specifiers indicate that the field to be edited occupies w positions. d indicates that the fractional part of the number (the part to the right of the decimal point) has d digits. However, if the input datum contains a decimal point, that decimal point overrides the d value.
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5
On input, the specified list item becomes defined with a real datum. On output, the specified list item must be defined as a real datum.
In an output statement, the
D
edit descriptor does the same thing as the
E
edit descriptor, except that a
D
is used in place of an
E
. The output field for the
D
w.d edit specifier has the width w. The value is right-justified in that field. The field consists of zero or more leading blanks followed by either a minus if the value is negative, or an optional plus, followed by the magnitude of the value of the list item rounded to d decimal digits.
w must allow for a minus sign, at least one digit to the left of the decimal point, the decimal point, and d digits to the right of the decimal point. Therefore, it must be the case that w
≥
w+3.
Example: Real input with
D
editing in the program,
Dinp.f
:
CHARACTER LINE*24 / '12345678 23.5678 .345678' /
READ( LINE, '( D8.3, D8.3, D8.3 )') R, S, T
PRINT '( D10.3, D11.4, D13.6 )', R, S, T
END
The above program displays:
0.123D+05 0.2357D+02 0.345678D+00
In the above example, the first input data item has no decimal point, so
D8.3
determines the decimal point. The other input data items have decimal points, so those decimal points override the
D
edit descriptor as far as decimal points are concerned.
Example: Real output with
D
editing in the program
Dout.f
:
R = 1234.678
PRINT 1, R, R, R
1 FORMAT( D9.3 / D8.4 / D13.4 )
END
Input and Output
285
5
286
The above program displays:
0.123D+04
********
∆∆∆
0.1235D+04
In the above example, the second printed line is asterisks because the
D8.4
does not allow for the sign; in the third printed line the
D13.4
results in three leading blanks.
E Editing
The
E
specifier is for the exponential form of decimal real data items. The general form is:
E [
w
[ .
d
] [ E
e
] ]
w indicates that the field to be edited occupies w positions.
d indicates that the fractional part of the number (the part to the right of the decimal point) has d digits. However, if the input datum contains a decimal point, that decimal point overrides the d value.
e indicates the number of digits in the exponent field. The default is 2.
The specified input/output list item must be of type real. On input, the specified list item becomes defined with a real datum. On output, the specified list item must be defined as a real datum.
The output field for the
E
w.d edit specifier has the width w. The value is rightjustified in that field. The field consists of zero or more leading blanks followed by either a minus if the value is negative, or an optional plus, followed by a zero, a decimal point, the magnitude of the value of the list item rounded to d decimal digits, and an exponent.
For the form
E
w
.
d:
•
If | exponent |
≤
99, it has the form
E
±
nn or
0
±
nn.
•
If 99
≤
| exponent |
≤
999, it has the form
±
nnn.
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5
For the form
E
w
.
d
E
e, if | exponent |
≤
( 10 e form
±
nnn.
) - 1, then the exponent has the
For the form
D
w
.
d:
•
If | exponent |
≤
99, it has the form
D
±
nn or
E
±
nn or
0
±
nn.
•
If 99
≤
| exponent |
≤
999, it has the form
±
nnn.
n is any digit.
The sign in the exponent is required.
w need not allow for a minus sign, but must allow for a zero, the decimal point, and d digits to the right of the decimal point, and an exponent.
Therefore, for nonnegative numbers, w
≥
d+6; if e is present, then w
≥
d+e+4.
For negative numbers, w
≥
d+7; if e is present, then w
≥
d+e+5.
Example: Real input with
E
editing in the program,
Einp.f
:
* 123456789 23456789012 23456789012
CHARACTER L*40/'1234567E2 1234.67E-3 12.4567 '/
READ( L, '( E9.3, E12.3, E12.6 )') R, S, T
PRINT '( E15.6, E15.6, E15.7 )', R, S, T
END
The above program displays:
∆∆∆
0.123457E+06
∆∆∆
0.123467E+01
∆∆
0.1245670E+02
In the above example, the first input data item has no decimal point, so
E9.3
determines the decimal point. The other input data items have decimal points, so those decimal points override the
D
edit descriptor as far as decimal points are concerned.
Example: Real output with
E
editing in the program
Eout.f
:
R = 1234.678
PRINT 1, R, R, R
1 FORMAT( E9.3 / E8.4 / E13.4 )
END
Input and Output
287
5
288
The above program displays:
0.123E+04
********
∆∆∆
0.1235E+04
In the above example,
E8.4
does not allow for the sign, so we get asterisks.
Also, the extra wide field of the
E13.4
results in three leading blanks.
Example: Real output with
E
w.d
E
e editing in the program
EwdEe.f
:
REAL X / 0.000789 /
WRITE(*,'( E13.3)') X
WRITE(*,'( E13.3E4)') X
WRITE(*,'( E13.3E5)') X
END
The above program displays:
∆∆∆∆
0.789E-03
∆∆
0.789E-0003
∆
0.789E-00003
F Editing
The
F
specifier is for decimal real data items. The general form is:
F [
w
[ .
d
] ]
The
F
w and
F
w.d edit specifiers indicate that the field to be edited occupies w positions.
d indicates that the fractional part of the number (the part to the right of the decimal point) has d digits. However, if the input datum contains a decimal point, that decimal point overrides the d value.
The specified input/output list item must be of type real. On input, the specified list item becomes defined with a real datum. On output, the specified list item must be defined as a real datum.
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5
The output field for the
F
w.d edit specifier has the width w. The value is rightjustified in that field. The field consists of zero or more leading blanks followed by either a minus if the value is negative, or an optional plus, followed by the magnitude of the value of the list item rounded to d decimal digits.
w must allow for a minus sign, at least one digit to the left of the decimal point, the decimal point, and d digits to the right of the decimal point. Therefore, it must be the case that w
≥
d+3.
Example: Real input with
F
editing in the program
Finp.f
:
CHARACTER LINE*24 / '12345678 23.5678 .345678' /
READ( LINE, '( F8.3, F8.3, F8.3 )') R, S, T
PRINT '( F9.3, F9.4, F9.6 )', R, S, T
END
The program displays:
12345.678DD23.5678D0.345678
In the above example, the first input data item has no decimal point, so
F8.3
determines the decimal point. The other input data items have decimal points, so those decimal points override the
F
edit descriptor as far as decimal points are concerned.
Example: Real output with
F
editing in the program
Fout.f
:
R = 1234.678
PRINT 1, R, R, R
1 FORMAT( F9.3 / F8.4 / F13.4 )
END
The above program displays:
∆
1234.678
********
∆∆∆∆
1234.6780
Input and Output
289
5
290
In the above example,
F8.4
does not allow for the sign;
F13.4
results in four leading blanks and one trailing zero.
G Editing
The
G
specifier is for decimal real data items. The general form is:
G [
w
[ .
d
] ] or:
G
w
.
d
E
e
The
D
,
E
,
F
, and
G
edit specifiers interpret data in the same way.
The representation for output by the
G
edit descriptor depends on the magnitude of the internal datum. In the following table, N is the magnitude of the internal datum.
Range
0.1
≤
N < 1.0
1.0
≤
N < 10.0
…
10
(d-2)
10
(d-1) ≤
≤
N
≤
10
N < 10
(d-1) d
Form
F
(w-
4
).d, n(
∆
)
F
(w-
4
).(d-1), n(
∆
)
…
F
(w-
4
).1, n(
∆
)
F
(w-
4
).0, n(
∆
)
Commas in Formatted Input
If you are entering numeric data that is controlled by a fixed-column format, then you can use commas to override any exacting column restrictions.
Example: Format:
(I10, F20.10, I4)
Using the above format reads the following record correctly:
–345,.05e–3,12
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5
The I/O system is just being more lenient than described in the FORTRAN 77
Standard. In general, when doing a formatted read of noncharacter variables, commas override field lengths. More precisely, for the
I
w,
F
w.d,
E
w.d[
E
e], and
G
w.d input fields, the field ends when w characters have been scanned, or a comma has been scanned, whichever occurs first. If it is a comma, the field consists of the characters up to, but not including, the comma; the next field begins with the character following the comma.
Remaining Characters (
Q
)
The
Q
edit descriptor gets the length of an input record or the remaining portion of it that is unread. ♦ It gets the number of characters remaining to be read from the current record.
Example: From a real and a string, get: real, string length, and string: demo% cat qed1.f
* qed1.f Q edit descriptor (real & string)
CHARACTER CVECT(80)*1
OPEN ( UNIT=4, FILE='qed1.data' )
READ ( 4, 1 ) R, L, ( CVECT(I), I=1,L )
1 FORMAT ( F4.2, Q, 80 A1 )
WRITE ( *, 2 ) R, L, '"', (CVECT(I),I=1,L), '"'
2 FORMAT ( 1X, F7.2, 1X, I2, 1X, 80A1 )
END demo% cat qed1.data
8.10qwerty
demo% f77 qed1.f -o qed1 qed1.f:
MAIN: demo% qed1
8.10 6 "qwerty" demo%
The above program reads a field into the variable
R
, then reads the number of characters remaining after that field into
L
, then reads
L
characters into
CVECT
.
Q
as the nth edit descriptor matches with
L
as the nth element in the
READ
list.
Input and Output
291
5
292
Example: Get length of input record; put the
Q
descriptor first: demo% cat qed2.f
CHARACTER CVECT(80)*1
OPEN ( UNIT=4, FILE='qed2.data' )
READ ( 4, 1 ) L, ( CVECT(I), I=1,L )
1 FORMAT ( Q, 80A1 )
WRITE ( *, 2 ) L, '"', (CVECT(I),I=1,L), '"'
2 FORMAT ( 1X, I2, 1X, 80A1 )
END demo% cat qed2.data qwerty demo% f77 qed2.f -o qed2 qed2.f:
MAIN: demo% qed2
6 "qwerty" demo%
The above example gets the length of the input record. With the whole input string and its length, you can then parse it yourself.
Several restrictions on the
Q
edit descriptor apply:
•
The list element
Q
corresponds to must be of
INTEGER
or
LOGICAL
data type.
•
Q
does strictly a character count. It gets the number of characters remaining in the input record, and does not get the number of integers or reals or anything else.
•
The
Q
edit descriptor cannot be applied for pipe files, as
Q
edit requires that the file be rereadable.
•
This descriptor operates on files and stdin
(terminal) input.
•
This descriptor is ignored for output.
Scale Factor (
P
)
The
P
edit descriptor scales real input values by a power of 10. It also gives you more control over the significant digit displayed for output values.
FORTRAN 77 Reference Manual
5
The general form is:
[
k
] P
k
Integer constant, with an optional sign
k is called the scale factor, and the default value is zero.
Example: I/O statements with scale factors:
READ ( 1, '( 3P E8.2 )' ) X
WRITE ( 1, '( 1P E8.2 )' ) X
P
by itself is equivalent to
0P
. It resets the scale factor to the default value
0P
.
This
P
by itself is nonstandard.
Scope
The scale factor is reset to zero at the start of execution of each I/O statement.
The scale factor can have an effect on
D
,
E
,
F
, and
G
edit descriptors.
Input
On input, any external datum that does not have an exponent field is divided by 10k before it is stored internally.
Input examples: Showing data, scale factors, and resulting value stored:
Data
Format
Memory
18.63
E8.2
18.63
18.63
3P E8.2
.01863
18.63E2
3P E8.2
18.63E2
18.63
-3P E8.2
18630.
Output
On output, with
D
, and
E
descriptors, and with
G
descriptors if the
E
editing is required, the internal item gets its basic real constant part multiplied by 10 k
, and the exponent is reduced by k before it is written out.
On output with the
F
descriptor and with
G
descriptors, if the
F
editing is sufficient, the internal item gets its basic real constant part multiplied by 10 k before it is written out.
Input and Output
293
5
294
Output Examples: Showing value stored, scale factors, and resulting output:
Memory
Format
Display
290.0
2P E9.3
29.00E+01
290.0
1P E9.3
290.0
-1P E9.3
2.900E+02 0.029E+04
290.0
F9.3
0.290E+03
Sign Editing (
SU
,
SP
,
SS
,
S
)
The
SU
,
SP
, and
S
edit descriptors control leading signs for output. For normal output, without any specific sign specifiers, if a value is negative, a minus sign is printed in the first position to the left of the leftmost digit; if the value is positive, printing a plus sign depends on the implementation, but f77
omits the plus sign.
The following sign specifiers are available:
•
SP
—If
SP
precedes a specification, a sign is printed.
•
SS
—If
SS
precedes a specification, plus-sign printing is suppressed.
•
S
—If
S
precedes a specification, the system default is restored. The default is
SS
.
•
SU
—If
SU
precedes a specification, integer values are interpreted as unsigned. This is nonstandard. ♦
For example, the unsigned specifier can be used with the radix specifier to format a hexadecimal dump, as follows:
2000 FORMAT( SU, 16R, 8I10.8 )
The rules and restrictions for sign control are:
•
Sign-control specifiers apply to output only.
•
A sign-control specifier remains in effect until another sign-control specifier is encountered, or format interpretation is complete.
•
The
S
,
SP
, and
SS
specifiers affect only
I
,
F
,
E
,
D
, and
G
editing.
•
The
SU
specifier affects only
I
editing.
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5
Slash Editing (
/
)
The slash (
/
) edit specifier indicates the end of data transfer on the current record.
Sequential Access
On input, any remaining portion of the current record is skipped, and the file is positioned at the beginning of the next record. Two successive slashes (
//
) skip a whole record.
On output, an end-of-record is written, and a new record is started. Two successive slashes (
//
) produce a record of no characters. If the file is an internal file, that record is filled with blanks.
Direct Access
Each slash increases the record number by one, and the file is positioned at the start of the record with that record number.
On output, two successive slashes (
//
) produce a record of no characters, and that record is filled with blanks.
Termination Control (
:
)
The colon (
:
) edit descriptor allows for conditional termination of the format.
If the I/O list is exhausted before the format, then the format terminates at the colon.
Example: Termination control:
* col1.f The colon (:) edit descriptor
DATA INIT / 3 /, LAST / 8 /
WRITE ( *, 2 ) INIT
WRITE ( *, 2 ) INIT, LAST
2 FORMAT ( 1X 'INIT = ', I2, :, 3X, 'LAST = ', I2 )
END
Input and Output
295
5
The above program produces output like the following
INIT = 3
INIT = 3 LAST = 8
Without the colon, the output is more like this:
INIT = 3 LAST =
INIT = 3 LAST = 8
Runtime Formats
You can put the format specifier into an object that you can change during execution. Doing so improves flexibility. There is some increase in execution time because this kind of format specifier is parsed every time the I/O statement is executed. These are also called variable formats.
The object must be one of the following kinds:
•
Character expression
—The character expression can be a scalar, an array, an element of an array, a substring, a field of a structured record ♦, the concatenation of any of the above, and so forth.
•
Integer array ♦ —The integer array can get its character values by a
DATA statement, an assignment statement, a
READ
statement, and so forth.
You must provide the delimiting left and right parentheses, but not the word
FORMAT
, and not a statement number.
You must declare the object so that it is big enough to hold the entire format.
For instance,
'(8X,12I)'
does not fit in an
INTEGER*4
or a
CHARACTER*4 object.
296
FORTRAN 77 Reference Manual
Examples: Runtime formats in character expressions and integer arrays: demo% cat runtim.f
CHARACTER CS*8
CHARACTER CA(1:7)*1 /'(','1','X',',','I','2',')'/
CHARACTER S(1:7)*6
INTEGER*4 IA(2)
STRUCTURE / STR /
CHARACTER*4 A
INTEGER*4 K
END STRUCTURE
CHARACTER*8 LEFT, RIGHT
RECORD /STR/ R
N = 9
CS = '(I8)'
WRITE( *, CS ) N !
Character Scalar
CA(2) = '6'
WRITE( *, CA ) N !
Character Array
S(2) = '(I8)'
WRITE( *, S(2) ) N !
Element of Character Array
IA(1) = '(I8)'
WRITE(*, IA ) N !
Integer Array
R.A = '(I8)'
WRITE( *, R.A ) N !
Field Of Record
LEFT = '(I'
RIGHT = '8)'
WRITE(*, LEFT // RIGHT ) N !
Concatenate
END demo% f77 -silent runtim.f demo% a.out
9
9
9
9
9
9 demo%
5
Variable Format Expressions (
<
e
>
)
In general, inside a
FORMAT
statement, any integer constant can be replaced by an arbitrary expression. ♦
Input and Output
297
298
5
The expression itself must be enclosed in angle brackets.
For example, the
6
in:
1 FORMAT( 3F6.1 ) can be replaced by the variable
N
, as in:
1 FORMAT( 3F<N>.1 ) or by the slightly more complicated expression
2*N+M
, as in:
1 FORMAT( 3F<2*N+M>.1 )
Similarly, the
3
or
1
can be replaced by any expression.
The single exception is the n in an n
H
…
edit descriptor.
The rules and restrictions for variable format expressions are:
•
The expression is reevaluated each time it is encountered in a format scan.
•
If necessary, the expression is converted to integer type.
•
Any valid FORTRAN 77 expression is allowed, including function calls.
•
Variable expressions are not allowed in formats generated at runtime.
•
The n in an n
H
…
edit descriptor cannot be a variable expression.
5.5 Unformatted I/O
Unformatted I/O is used to transfer binary information to or from memory locations without changing its internal representation. Each execution of an unformatted I/O statement causes a single logical record to be read or written.
Since internal representation varies with different architectures, unformatted
I/O is limited in its portability.
You can use unformatted I/O to write data out temporarily, or to write data out quickly for subsequent input to another FORTRAN 77 program running on a machine with the same architecture.
FORTRAN 77 Reference Manual
5
Sequential Access I/O
Logical record length for unformatted, sequential files is determined by the number of bytes required by the items in the I/O list. The requirements of this form of I/O cause the external physical record size to be somewhat larger than the logical record size.
Example:
WRITE( 8 ) A, B
The FORTRAN 77 runtime system embeds the record boundaries in the data by inserting an
INTEGER*4
byte count at the beginning and end of each unformatted sequential record during an unformatted sequential
WRITE
. The trailing byte count enables
BACKSPACE
to operate on records. The result is that
FORTRAN 77 programs can use an unformatted sequential
READ
only on data that was written by an unformatted sequential
WRITE
operation. Any attempt to read such a record as formatted would have unpredictable results.
Here are some guidelines:
•
Avoid using the unformatted sequential
READ
unless your file was written that way.
•
Because of the extra data at the beginning and end of each unformatted sequential record, you might want to try using the unformatted direct
I/O whenever that extra data is significant. It is more significant with short records than with very long ones.
Direct Access I/O
If your I/O lists are different lengths, you can
OPEN
the file with the
RECL=1 option. This signals FORTRAN 77 to use the I/O list to determine how many items to read or write.
For each read, you still must tell it the initial record to start at, in this case which byte, so you must know the size of each item. ♦
A simple example follows.
Input and Output
299
5
Example: Direct access—write 3 records, 2 integers each: demo% cat Direct1.f integer u/4/, v /5/, w /6/, x /7/, y /8/, z /9/ open( 1, access='DIRECT', recl=8 ) write( 1, rec=1 ) u, v write( 1, rec=2 ) w, x write( 1, rec=3 ) y, z end demo% f77 -silent Direct1.f demo% a.out demo%
If you know record length is
n
, then you can use the recl=
n
option.
Here you read it as it was written.
This method is simpler, easier, and better.
Example: Direct access—read 3 records, 2 integers each: demo% cat Direct2.f integer u, v, w, x, y, z open( 1, access='DIRECT', recl=8 ) read( 1, rec=1 ) u, v read( 1, rec=2 ) w, x read( 1, rec=3 ) y, z write(*,*) u, v, w, x, y, z end demo% f77 -silent Direct2.f demo% a.out
4 5 6 7 8 9 demo%
Example: Direct-access read, variable-length records, recl=1
:
If you know the size of each item, but not the record length, then you can use the recl=1
option.
Here you can read it using different record lengths than it was written with.
This method is trickier.
demo% cat Direct3.f integer u, v, w, x, y, z open( 1, access='DIRECT', recl=1 ) read( 1, rec=1 ) u, v, w read( 1, rec=13 ) x, y, z write(*,*) u, v, w, x, y, z end demo% f77 -silent Direct3.f demo% a.out
4 5 6 7 8 9 demo%
300
FORTRAN 77 Reference Manual
5
In the above example, after reading 3 integers (12 bytes), you start the next read at record 13.
5.6 List-Directed I/O
List-directed I/O is a free-form I/O for sequential access devices. To get it, use an asterisk as the format identifier, as in:
READ( 6, * ) A, B, C
Note these rules for list-directed input:
•
On input, values are separated by strings of blanks and, possibly, a comma.
•
Values, except for character strings, cannot contain blanks.
•
Character strings can be quoted strings, using pairs of quotes (
"
), pairs of apostrophes ('), or unquoted strings (see “Unquoted Strings”), but not hollerith (n
Hxyz
) strings.
•
End-of-record counts as a blank, except in character strings, where it is ignored.
•
Complex constants are given as two real constants separated by a comma and enclosed in parentheses.
•
A null input field, such as between two consecutive commas, means that the corresponding variable in the I/O list is not changed.
•
Input data items can be preceded by repetition counts, as in:
4*(3.,2.) 2*, 4*'hello'
The above input stands for 4 complex constants, 2 null input fields, and 4 string constants.
•
A slash (
/
) in the input list terminates assignment of values to the input list during list-directed input, and the remainder of the current input line is skipped. Any text that follows the slash is ignored and can be used to comment the data line.
Input and Output
301
5
302
Output Format
List-directed output provides a quick and easy way to print output without fussing with format details. If you need exact formats, use formatted I/O. A suitable format is chosen for each item, and where a conflict exists between complete accuracy and simple output form, the simple form is chosen.
Note these rules for list-directed output:
•
In general, each record starts with a blank space. For a print file, that blank is not printed. See “Printing Files,” for details. ♦
•
Character strings are printed as is. They are not enclosed in quotes, so only certain forms of strings can be read back using list-directed input. These forms are described in the next section.
•
A number with no exact binary representation is rounded off.
Example: No exact binary representation: demo% cat lis5.f
READ ( 5, * ) X
WRITE( 6, * ) X, ' beauty'
WRITE( 6, 1 ) X
1 FORMAT( 1X, F13.8, ' truth' )
END demo% f77 lis5.f lis5.f:
MAIN: demo% a.out
1.4
1.40000000 beauty
1.39999998 truth demo%
In the above example, if you need accuracy, specify the format.
Also note:
•
Output lines longer than 80 characters are avoided where possible.
•
Complex and double complex values include an appropriate comma.
•
Real, double, and quadruple precision values are formatted differently.
FORTRAN 77 Reference Manual
5
•
A backslashn
(
\n
) in a character string is output as a carriage return, unless the
–xl
option is on, and then it is output as a backslashn
(
\n
).
Example: List-directed I/O and backslash-n, with and without
-xl
: demo% cat f77 bslash.f
CHARACTER S*8 / '12\n3' /
PRINT *, S
END demo%
Without
–xl
,
\n
prints as a carriage return: demo% f77 -silent bslash.f demo% a.out
12
3 demo%
With
–xl
,
\n
prints as a character string: demo% f77 -xl -silent bslash.f demo% a.out
12\n3 demo%
Input and Output
303
304
5
Table 5-8
Default Formats for List-Directed Output
Type
BYTE
CHARACTER*
n
COMPLEX
COMPLEX*16
COMPLEX*32
(SPARC only)
INTEGER*2
INTEGER*4
INTEGER*8
LOGICAL*1
LOGICAL*2
LOGICAL*4
LOGICAL*8
REAL
REAL*8
REAL*16
(SPARC only)
Format
Two blanks followed by the number
A
n {n = length of character expression}
'
∆∆
(', 1PE14.5E2, ',', 1PE14.5E2, ')'
'
∆∆
(', 1PE22.13.E2, ',', 1PE22.13.E2, ')'
'
∆∆
(', 1PE44.34E3, ',', 1PE44.34E3, ')'
Two blanks followed by the number
Two blanks followed by the number
Two blanks followed by the number
Two blanks followed by the number
L3
L3
L3
1PE14.5E2
1PE22.13.E2
1PE44.34E4
Unquoted Strings
f77
list-directed I/O allows reading of a string not enclosed in quotes. ♦
The string must not start with a digit, and cannot contain separators (commas or slashes (
/
)) or whitespace (spaces or tabs). A newline terminates the string unless escaped with a backslash (
\
). Any string not meeting the above restrictions must be enclosed in single or double quotes.
Example: List-directed input of unquoted strings:
CHARACTER C*6, S*8
READ *, I, C, N, S
PRINT *, I, C, N, S
END
FORTRAN 77 Reference Manual
5
The above program, unquoted.f
, reads and displays as follows: demo% a.out
23 label 82 locked
23label 82locked demo%
Internal I/O
f77
extends list-directed I/O to allow internal I/O. ♦
During internal, list-directed reads, characters are consumed until the input list is satisfied or the end-of-file is reached. During internal, list-directed writes, records are filled until the output list is satisfied. The length of an internal array element should be at least 20 characters to avoid logical record overflow when writing double-precision values. Internal, list-directed read was implemented to make command line decoding easier. Internal, list-directed output should be avoided.
5.7
NAMELIST
I/O
NAMELIST
I/O produces format-free input or output of whole groups of variables, or input of selected items in a group of variables. ♦
The
NAMELIST
statement defines a group of variables or arrays. It specifies a group name, and lists the variables and arrays of that group.
Syntax Rules
The syntax of the
NAMELIST
statement is:
NAMELIST /
group-name
/
namelist
[[,]/
group-name/namelist
]
…
group-name namelist
Identifier
List of variables or arrays, separated by commas
Input and Output
305
5
306
Example:
NAMELIST
statement:
CHARACTER*18 SAMPLE
LOGICAL*4 NEW
REAL*4 DELTA
NAMELIST /CASE/ SAMPLE, NEW, DELTA
A variable or array can be listed in more than one
NAMELIST
group.
The input data can include array elements and strings. It can include substrings in the sense that the input constant data string can be shorter than the declared size of the variable.
Restrictions
group name can appear in only the
NAMELIST
,
READ
, or
WRITE
statements, and must be unique for the program.
list cannot include constants, dummy arguments, array elements, structures, substrings, records, record fields, pointers, or pointer-based variables.
Example: A variable in two
NAMELIST
groups:
REAL ARRAY(4,4)
CHARACTER*18 SAMPLE
LOGICAL*4 NEW
REAL*4 DELTA
NAMELIST /CASE/ SAMPLE, NEW, DELTA
NAMELIST /GRID/ ARRAY, DELTA
In the above example,
DELTA
is in the group
CASE
and in the group
GRID
.
Output Actions
NAMELIST
output uses a special form of
WRITE
statement, which makes a report that shows the group name. For each variable of the group, it shows the name and current value in memory. It formats each value according to the type of each variable, and writes the report so that
NAMELIST
input can read it.
FORTRAN 77 Reference Manual
5
The syntax of
NAMELIST WRITE
is:
WRITE (
extu, namelist-specifie
r [,
iostat
]
[, err
]) where namelist-specifier has the form:
[NML=]
group-name
and group-name has been previously defined in a
NAMELIST
statement.
The
NAMELIST WRITE
statement writes values of all variables in the group, in the same order as in the
NAMELIST
statement.
Example:
NAMELIST
output: demo% cat nam1.f
* nam1.f Namelist output
CHARACTER*8 SAMPLE
LOGICAL*4 NEW
REAL*4 DELTA
NAMELIST /CASE/ SAMPLE, NEW, DELTA
DATA SAMPLE /'Demo'/, NEW /.TRUE./, DELTA /0.1/
WRITE ( *, CASE )
END demo% f77 nam1.f f77 nam1.f
nam1.f:
MAIN: demo% a.out
∆
&case sample= Demo , new= T, delta= 0.100000
∆
&end demo%
↑
column 2
Note that if you do omit the keyword
NML
then the unit parameter must be first, namelist-specifier must be second, and there must not be a format specifier.
Input and Output
307
308
5
The
WRITE
can have the form of the following example:
WRITE ( UNIT=6, NML=CASE )
Input Actions
The
NAMELIST
input statement reads the next external record, skipping over column one, and looking for the symbol
$
in column two or beyond, followed by the group name specified in the
READ
statement.
If the $group-name is not found, the input records are read until end of file.
The records are input and values assigned by matching names in the data with names in the group, using the data types of the variables in the group.
Variables in the group that are not found in the input data are unaltered.
The syntax of
NAMELIST READ
is:
READ (
extu
,
namelist-specifier
[,
iostat
] [,
err
] [,
end
]) where namelist-specifier has the form:
[NML=]
group-name
and group-name has been previously defined in a
NAMELIST
statement.
Example:
NAMELIST
input:
CHARACTER*14 SAMPLE
LOGICAL*4 NEW
REAL*4 DELTA, MAT(2,2)
NAMELIST /CASE/ SAMPLE, NEW, DELTA, MAT
READ ( 1, CASE )
FORTRAN 77 Reference Manual
5
In this example, the group
CASE
consists of the variables,
SAMPLE
,
NEW
,
DELTA
, and
MAT
. If you do omit the keyword
NML
, then you must also omit the keyword
UNIT
. The unit parameter must be first, namelist-specifier must be second, and there must not be a format specifier.
The
READ
can have the form of the following example:
READ ( UNIT=1, NML=CASE )
Data Syntax
The first record of
NAMELIST
input data has the special symbol
$
(dollar sign) in column two or beyond, followed by the
NAMELIST
group name. This is followed by a series of assignment statements, starting in or after column two, on the same or subsequent records, each assigning a value to a variable (or one or more values to array elements) of the specified group. The input data is terminated with another
$
in or after column two, as in the pattern:
∆
$
group-name variable=value
[,
variable=value,…
] $[END
]
You can alternatively use an ampersand (
&
) in place of each dollar sign, but the beginning and ending delimiters must match.
END
is an optional part of the last delimiter.
The input data assignment statements must be in one of the following forms: variable=value array=value1[, value2,]… array(subscript)=value1[, value2,]… array(subscript,subscript)=value1[, value2,]… variable=character constant variable(index:index)=character constant
If an array is subscripted, it must be subscripted with the appropriate number of subscripts: 1, 2, 3,
…
Input and Output
309
310
5
Use quotes (either
"
or
'
) to delimit character constants. For more on character constants, see the next section.
The following is sample data to be read by the program segment above:
Here
NEW
was not input, and the order is not the same as in the example
NAMELIST
statement.
∆
$case delta=0.05, mat( 2, 2 ) = 2.2, sample='Demo' $
↑
column 2
The data could be on several records:
∆
$case
∆ delta=0.05
∆ mat( 2, 2 ) = 2.2
∆ sample='Demo'
∆
$
↑
column 2
Syntax Rules
The following syntax rules apply for input data to be read by
NAMELIST
:
•
The variables of the named group can be in any order, and any can be omitted.
•
The data must start in or after column two. Column one is totally ignored.
•
There must be at least one comma, space, or tab between variables, and one or more spaces or tabs are the same as a single space. Consecutive commas are not permitted before a variable name. Spaces before or after a comma have no effect.
•
No spaces or tabs are allowed inside a group name or a variable name, except around the commas of a subscript, around the colon of a substring, and after the
(
and before the
)
marks. No name can be split over two records.
•
The end of a record acts like a space character.
FORTRAN 77 Reference Manual
5
Note an exception—in a character constant, it is ignored, and the character constant is continued with the next record. The last character of the current record is immediately followed by the second character of the next record.
The first character of each record is ignored.
•
The equal sign of the assignment statement can have zero or more blanks or tabs on each side of it.
•
Only constant values can be used for subscripts, range indicators of substrings, and the values assigned to variables or arrays. You cannot use a symbolic constant (parameter) in the actual input data.
Hollerith, octal, and hexadecimal constants are not permitted.
Each constant assigned has the same form as the corresponding
FORTRAN 77 constant.
There must be at least one comma, space, or tab between constants. Zero or more spaces or tabs are the same as a single space. You can enter:
1,2,3
, or
1 2 3
, or
1, 2, 3
, and so forth.
Inside a character constant, consecutive spaces or tabs are preserved, not compressed.
A character constant is delimited by apostrophes (
'
) or quotes (
"
), but if you start with one of those, you must finish that character constant with the same one. If you use the apostrophe as the delimiter, then to get an apostrophe in a string, use two consecutive apostrophes.
Example: Character constants:
∆ sample='use "$" in 2'
(Goes in as: use
$
in 2)
∆ sample='don''t'
(Goes in as: don't)
∆ sample="don''t"
∆ sample="don't"
(Goes in as: don''t)
(Goes in as: don't)
A complex constant is a pair of real or integer constants separated by a comma and enclosed in parentheses. Spaces can occur only around the punctuation.
A logical constant is any form of true or false value, such as
.TRUE.
or
.FALSE.
, or any value beginning with
.T, .F
, and so on.
Input and Output
311
5
312
A null data item is denoted by two consecutive commas, and it means the corresponding array element or complex variable value is not to be changed.
Null data item can be used with array elements or complex variables only. One null data item represents an entire complex constant; you cannot use it for either part of a complex constant.
Example:
NAMELIST
input with some null data:
* nam2.f Namelist input with consecutive commas
REAL ARRAY(4,4)
NAMELIST /GRID/ ARRAY
WRITE ( *, * ) 'Input?'
READ ( *, GRID )
WRITE ( *, GRID )
END
The data for nam2.f
is:
∆
$GRID ARRAY = 9,9,9,9,,,,,8,8,8,8 $
↑
column 2
↑
5 consecutive commas
This code loads 9s into row 1, skips 4 elements, and loads 8s into row 3 of
ARRAY
.
Arrays Only
The forms r
*
c and r* can be used only with an array.
The form r*c stores r copies of the constant c into an array, where r is a nonzero, unsigned integer constant, and c is any constant.
Example:
NAMELIST
with repeat-factor in data:
* nam3.f Namelist "r*c" and "r* "
REAL PSI(10)
NAMELIST /GRID/ PSI
WRITE ( *, * ) 'Input?'
READ ( *, GRID )
WRITE ( *, GRID )
END
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5
The input for nam3.f
is:
∆
$GRID PSI = 5*980 $
↑
column 2
The program, nam3.f
, reads the above input and loads 980.0 into the first 5 elements of the array
PSI
.
•
The form r* skips r elements of an array (that is, does not change them), where r is an unsigned integer constant.
Example:
NAMELIST
input with some skipped data.
The other input is:
∆
$GRID PSI = 3* 5*980 $
↑
column 2
The program, nam3.f
, with the above input, skips the first 3 elements and loads 980.0 into elements 4,5,6,7,8 of
PSI
.
Name Requests
If your program is doing
NAMELIST
input from the terminal, you can request the group name and
NAMELIST
names that it accepts.
To do so, enter a question mark (
?
) in column two and press Return. The group name and variable names are then displayed. The program then waits again for input.
Input and Output
313
5
User input 1
→
User input 2
→
Example: Requesting names: demo% cat nam4.f
* nam4.f Namelist: requesting names
CHARACTER*14 SAMPLE
LOGICAL*4 NEW
REAL*4 DELTA
NAMELIST /CASE/ SAMPLE, NEW, DELTA
WRITE ( *, * ) 'Input?'
READ ( *, CASE )
END demo% f77 -silent nam4.f demo% a.out
Input?
∆
?
∆
$case
∆ sample
∆ new
∆ delta
D
∆
$case sample="Test 2", delta=0.03 $ demo%
↑
column 2
314
FORTRAN 77 Reference Manual
Intrinsic Functions
6
This chapter contains a number of tables on intrinsic functions, as well as some explanatory notes. It is organized into the following sections:
Arithmetic and Mathematical Functions
Character Functions
Miscellaneous Functions
VMS Intrinsic Functions page 315 page 324 page 325 page 332
6.1 Arithmetic and Mathematical Functions
This section provides details on arithmetic functions, type conversions, trigonometric functions, and other functions.
315
6
Intrinsic Function
Truncation
See Note (1).
Arithmetic
Definition
int(a)
Table 6-1
Arithmetic Functions
No. of
Args.
1
Generic
Name
AINT
Nearest whole number int(a+.5) if a
≥
0 int(a-.5) if a < 0
1
ANINT
Nearest integer int(a+.5) if a
≥
0 int(a-.5) if a < 0
1
NINT
Specific
Names
AINT
DINT
QINT
♦
ANINT
DNINT
QNINT
♦
NINT
IDNINT
IQNINT
♦
Argument
Type
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
(SPARC only)
REAL
DOUBLE
REAL*16
Function
Type
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
INTEGER
INTEGER
INTEGER
Intrinsic Function
Absolute value
See Note (6).
Remainder
See Note (1).
Transfer of sign
Definition
|a|
Table 6-2
More Arithmetic Functions
No. of
Args.
1
Generic
Name
ABS
(ar
2
+ ai
2
)**(1/2) a1-int(a1/a2)*a2
|a1| if a2
≥
0
-|a1| if a2
<
0
2
2
MOD
SIGN
Specific
Name
IABS
ABS
DABS
CABS
QABS
ZABS
CDABS
CQABS
♦
♦
♦
♦
MOD
AMOD
DMOD
QMOD
♦
ISIGN
SIGN
DSIGN
QSIGN
♦
Argument
Type
INTEGER
REAL
DOUBLE
COMPLEX
REAL*16
COMPLEX*16
COMPLEX*16
COMPLEX*32
INTEGER
REAL
DOUBLE
REAL*16
INTEGER
REAL
DOUBLE
REAL*16
Function
Type
INTEGER
REAL
DOUBLE
REAL
REAL*16
DOUBLE
DOUBLE
REAL*16
INTEGER
REAL
DOUBLE
REAL*16
INTEGER
REAL
DOUBLE
REAL*16
316
FORTRAN 77 Reference Manual
Intrinsic Function
Positive difference
Choosing largest value
Choosing smallest value
Table 6-2
More Arithmetic Functions (Continued)
Definition
a1-a2 if a1
>
a2
0 if a1
≤
a2
Double and quad products a1 * a2 max(a1, a2, …) min(a1, a2, …)
No. of
Args.
2
2
≥
2
≥
2
Generic
Name
DIM
-
MAX
MIN
Specific
Name
IDIM
DIM
DDIM
QDIM
♦
DPROD
QPROD
♦
MAX0
AMAX1
DMAX1
QMAX1
AMAX0
MAX1
♦
MIN0
AMIN1
DMIN1
QMIN1
AMIN0
MIN1
♦
Argument
Type
INTEGER
REAL
DOUBLE
REAL*16
REAL
DOUBLE
INTEGER
REAL
DOUBLE
REAL*16
INTEGER
REAL
INTEGER
REAL
DOUBLE
REAL*16
INTEGER
REAL
Function
Type
INTEGER
REAL
DOUBLE
REAL*16
DOUBLE
REAL*16
INTEGER
REAL
DOUBLE
REAL*16
REAL
INTEGER
INTEGER
REAL
DOUBLE
REAL*16
REAL
INTEGER
6
Intrinsic Functions
317
6
Type Conversion
Conversion to
INTEGER
See Note (1).
REAL
See Note (2).
DOUBLE
See Note (3).
REAL*16
See Note (3’).
No. of
Arguments
1
1
1
1
Table 6-3
Type Conversion Functions
Generic
Name
INT
REAL
DBLE
QREAL
QEXT
Specific Name
-
INT
IFIX
IDINT
-
-
-
IQINT
♦
-
-
-
REAL
FLOAT
-
SNGL
-
-
-
-
-
SNGLQ
♦
DBLE
DFLOAT
DREAL
♦
-
-
DBLEQ
-
-
QREAL
♦
QFLOAT
QEXT
♦
QEXTD
♦
♦
Argument Type
INTEGER
REAL
REAL
DOUBLE
COMPLEX
COMPLEX*16
COMPLEX*32
REAL*16
INTEGER
INTEGER
REAL
DOUBLE
REAL*16
COMPLEX
COMPLEX*16
COMPLEX*32
DOUBLE
REAL*16
COMPLEX
COMPLEX*16
COMPLEX*32
INTEGER
INTEGER
REAL
DOUBLE
REAL*16
COMPLEX
COMPLEX*16
COMPLEX*32
INTEGER
INTEGER
INTEGER
DOUBLE
COMPLEX
COMPLEX*16
COMPLEX*32
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
Function Type
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
REAL*16
REAL*16
REAL*16
REAL*16
REAL*16
REAL*16
REAL*16
318
FORTRAN 77 Reference Manual
6
Conversion to
COMPLEX
See Notes (4) and (8).
No. of
Arguments
1 or 2
COMPLEX*16
See Note (8).
COMPLEX*32
See Note (8).
INTEGER
See Note (5).
CHARACTER
See Note (5).
1 or 2
1 or 2
1
1
Table 6-3
Type Conversion Functions (Continued)
DCMPLX
QCMPLX
-
-
-
-
Generic
Name
CMPLX
-
-
-
-
-
-
-
Specific Name
-
-
-
-
-
-
-
-
-
-
-
-
-
-
ICHAR
IACHAR
♦
CHAR
ACHAR
♦
Argument Type
INTEGER
REAL
DOUBLE
REAL*16
COMPLEX
COMPLEX*16
COMPLEX*32
INTEGER
REAL
DOUBLE
REAL*16
COMPLEX
COMPLEX*16
COMPLEX*32
INTEGER
REAL
DOUBLE
REAL*16
COMPLEX
COMPLEX*16
COMPLEX*32
CHARACTER
INTEGER
Function Type
COMPLEX
COMPLEX
COMPLEX
COMPLEX
COMPLEX
COMPLEX
COMPLEX
DOUBLE COMPLEX
DOUBLE COMPLEX
DOUBLE COMPLEX
DOUBLE COMPLEX
DOUBLE COMPLEX
DOUBLE COMPLEX
DOUBLE COMPLEX
COMPLEX*32
COMPLEX*32
COMPLEX*32
COMPLEX*32
COMPLEX*32
COMPLEX*32
COMPLEX*32
INTEGER
CHARACTER
On an ASCII machine, including Sun systems:
•
ACHAR
is a nonstandard synonym for
CHAR
•
IACHAR
is a nonstandard synonym for
ICHAR
On a non-ASCII machine,
ACHAR
and
IACHAR
were intended to provide a way to deal directly with ASCII.
Intrinsic Functions
319
6
Trigonometric Functions
Intrinsic Function
Sine
See Note (7).
Sine (degrees)
See Note (7).
Cosine
See Note (7).
Cosine (degrees)
See Note (7).
Tangent
See Note (7).
Tangent (degrees)
See Note (7).
Arcsine
See Note (7).
Arcsine (degrees)
See Note (7).
Definition
sin(a) sin(a) cos(a) cos(a) tan(a) tan(a) arcsin(a) arcsin(a)
Table 6-4
Trigonometric Functions
No. of
Args.
1
1
1
1
1
1
1
1
Generic
Name
SIN
SIND
COS
COSD
TAN
TAND
ASIN
ASIND
♦
♦
♦
♦
Specific Name
SIN
DSIN
QSIN
CSIN
ZSIN
♦
CDSIN
♦
CQSIN
♦
SIND
♦
DSIND
♦
QSIND
♦
COS
DCOS
QCOS
CCOS
ZCOS
♦
CDCOS
♦
CQCOS
♦
COSD
♦
DCOSD
♦
QCOSD
♦
TAN
DTAN
QTAN
♦
TAND
♦
DTAND
♦
QTAND
♦
ASIN
DASIN
QASIN
♦
ASIND
♦
DASIND
♦
QASIND
♦
Argument Type
REAL
DOUBLE
REAL*16
COMPLEX
DOUBLE COMPLEX
DOUBLE COMPLEX
COMPLEX*32
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
COMPLEX
DOUBLE COMPLEX
DOUBLE COMPLEX
COMPLEX*32
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
Function Type
REAL
DOUBLE
REAL*16
COMPLEX
DOUBLE COMPLEX
DOUBLE COMPLEX
COMPLEX*32
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
COMPLEX
DOUBLE COMPLEX
DOUBLE COMPLEX
COMPLEX*32
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
320
FORTRAN 77 Reference Manual
Intrinsic Function
Arccosine
See Note (7).
Arccosine (degrees)
See Note (7).
Arctangent
See Note (7).
Arctangent (degrees)
See Note (7).
Hyperbolic Sine
See Note (7).
Hyperbolic Cosine
See Note (7).
Hyperbolic Tangent
See Note (7).
Definition
arccos(a) arccos(a) arctan(a) arctan(a1/a2) arctan(a) arctan(a1/a2) sinh(a) cosh(a) tanh(a)
Table 6-4
Trigonometric Functions (Continued)
No. of
Args.
1
1
1
2
1
2
1
1
1
Generic
Name
ACOS
ACOSD
ATAN
♦
ATAN2 ATAN2
DATAN2
QATAN2
♦
ATAND
♦
ATAND
♦
DATAND
♦
QATAND
♦
ATAN2D
♦
ATAN2D
♦
DATAN2D
♦
QATAN2D
♦
SINH SINH
DSINH
QSINH
♦
COSH
TANH
COSH
DCOSH
QCOSH
♦
TANH
DTANH
QTANH
♦
Specific Name Argument Type
ACOS
DACOS
QACOS
♦
ACOSD
♦
DACOSD
♦
QACOSD
♦
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
ATAN
DATAN
QATAN
♦
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
REAL*16
and
COMPLEX*32
are SPARC only.
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
Function Type
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
6
Intrinsic Functions
321
6
Intrinsic Function
Imaginary part of a complex
See Note (6).
Conjugate of a complex
See Note (6).
Square root
Cube root
See Note(8’).
Exponential
Other Mathematical Functions
Natural logarithm ai
Table 6-5
Other Mathematical Functions
Definition
(ar, -ai) a**(1/2) a**(1/3) e**a log(a)
No. of
Args.
1
1
1
1
1
1
Generic
Name
IMAG
CONJG
SQRT
CBRT
EXP
LOG
Specific Name Argument Type Function Type
AIMAG
DIMAG
♦
QIMAG
♦
COMPLEX
COMPLEX*16
COMPLEX*32
REAL
DOUBLE
COMPLEX*32
CONJG
DCONJG
♦
QCONJG
♦
SQRT
DSQRT
QSQRT
CSQRT
ZSQRT
♦
CDSQRT
♦
CQSQRT
♦
CBRT
DCBRT
♦
♦
QCBRT
CCBRT
♦
♦
CDCBRT
CQCBRT
♦
♦
EXP
DEXP
QEXP
♦
CEXP
ZEXP
♦
CDEXP
♦
CQEXP
♦
ALOG
DLOG
QLOG
♦
CLOG
ZLOG
♦
CDLOG
♦
CQLOG
♦
COMPLEX
COMPLEX*16
COMPLEX*32
REAL
DOUBLE
REAL*16
COMPLEX
COMPLEX*16
COMPLEX*16
COMPLEX*32
REAL
DOUBLE
REAL*16
COMPLEX
COMPLEX*16
COMPLEX*32
REAL
DOUBLE
REAL*16
COMPLEX
COMPLEX*16
COMPLEX*16
COMPLEX*32
REAL
DOUBLE
REAL*16
COMPLEX
COMPLEX*16
COMPLEX*16
COMPLEX*32
COMPLEX
COMPLEX*16
COMPLEX*32
REAL
DOUBLE
REAL*16
COMPLEX
COMPLEX*16
COMPLEX*16
COMPLEX*32
REAL
DOUBLE
REAL*16
COMPLEX
COMPLEX*16
COMPLEX*32
REAL
DOUBLE
REAL*16
COMPLEX
COMPLEX*16
COMPLEX*16
COMPLEX*32
REAL
DOUBLE
REAL*16
COMPLEX
COMPLEX*16
COMPLEX*16
COMPLEX*32
322
FORTRAN 77 Reference Manual
Intrinsic Function
Common logarithm
Error function
Error function
6
Table 6-5
Other Mathematical Functions (Continued)
Definition
log10(a)
2/sqrt(pi)* integral from
0 to a of exp(-t*t) dt
1.0 - erf(a)
1
1
No. of
Args.
1
Generic
Name
LOG10
ERF
ERFC
Specific Name Argument Type Function Type
ALOG10
DLOG10
QLOG10
♦
ERF
DERF
♦
♦
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL
DOUBLE
REAL*16
REAL
DOUBLE
ERFC
DERFC
♦
♦
REAL
DOUBLE
REAL
DOUBLE
REAL*16
and
COMPLEX*32
are SPARC only.
Intrinsic Functions
323
6
6.2 Character Functions
Intrinsic Function
Conversion
See Note (5).
Definition
Table 6-6
Character Functions
Conversion to character
No. of
Args.
1
Conversion to integer 1
-
-
-
-
Generic
Name
2 -
Specific
Name
CHAR
ACHAR
♦
ICHAR
IACHAR
♦
(See also
Table 6-3.)
INDEX
Index of a substring Location of substring a2 in string a1
See Note (10).
Length
Lexically greater than or equal
Lexically greater than
Lexically less than or equal
Lexically less than
Length of character entity
See Note (11).
a1
≥
a2
See Note (12).
a1
>
a2
See Note (12).
a1
≤
a2
See Note (12).
a1
<
a2
See Note (12).
1
2
2
2
2 -
-
-
-
-
LEN
LGE
LGT
LLE
LLT
Argument Type Function Type
INTEGER CHARACTER
CHARACTER
CHARACTER
CHARACTER
CHARACTER
CHARACTER
CHARACTER
CHARACTER
INTEGER
INTEGER
INTEGER
LOGICAL
LOGICAL
LOGICAL
LOGICAL
On an ASCII machine (including Sun systems):
•
ACHAR
is a nonstandard synonym for
CHAR
•
IACHAR
is a nonstandard synonym for
ICHAR
On a non-ASCII machine,
ACHAR
and
IACHAR
were intended to provide a way to deal directly with ASCII.
324
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6
6.3 Miscellaneous Functions
Other miscellaneous functions include bitwise functions, environmental inquiry functions, and memory allocation and deallocation functions.
Bit Manipulation
Table 6-7
Bitwise Functions
Bitwise Operations
Complement
And
Inclusive or
Exclusive or
Shift
See Note (14).
Left shift
See Note (14).
Right shift
See Note (14).
Logical right shift
See Note (14).
Bit extraction
Bit set
Bit test
Bit clear
Circular shift
1
2
2
2
2
2
2
2
No. of
Args.
2
2
2
3
2
2
2
3
Specific Name
NOT
♦
AND
IAND
♦
♦
OR
IOR
♦
♦
XOR
IEOR
♦
♦
ISHFT
♦
Argument
Type
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
LSHIFT
♦
RSHIFT
♦
LRSHFT
♦
IBITS
♦
IBSET
♦
BTEST
♦
IBCLR
♦
ISHFTC
♦
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
Function Type
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
LOGICAL
INTEGER
INTEGER
The above functions are available as intrinsic or extrinsic functions. See also
“bit: Bit Functions: and, or, …, bit, setbit, …,” on page 342.
Intrinsic Functions
325
6
See Chapter 8, “VMS Language Extensions,” for details on other bitwise operations. ♦
Environmental Inquiry Functions
Definition
Base of Number System
Table 6-8
Environmental Inquiry Functions
No. of
Args.
1
Generic Name Specific Name
EPBASE
♦
-
Number of Significant Bits
Minimum Exponent
Maximum Exponent
Least Nonzero Number
Largest Number Representable
Epsilon
See Note (16).
1
1
1
1
1
1
EPPREC
♦
EPEMIN
♦
EPEMAX
♦
EPTINY
♦
EPHUGE
♦
EPMRSP
♦
-
-
-
-
-
-
Argument Type Function Type
INTEGER
REAL
DOUBLE
REAL*16
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
REAL
DOUBLE
REAL*16
INTEGER
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
INTEGER
REAL
DOUBLE
REAL*16
REAL
DOUBLE
REAL*16
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6
Intrinsic
Function
Location
Allocate
Deallocate
Size
Memory
Definition
Address of
See Note (17).
Table 6-9
Memory Functions
No. of
Args.
1 -
Generic
Name
Allocate memory and return address.
See Note (17).
Deallocate memory allocated by
MALLOC
.
Return the size of the argument in bytes.
See Note (18).
1
1
1 -
-
-
6.4 Remarks
Specific
Name
LOC
♦
MALLOC
♦
FREE
♦
SIZEOF
♦
Argument
Type
Any
INTEGER
Function
Type
INTEGER
INTEGER
Any
-
Any expression or type name
INTEGER
The following remarks apply to all of the intrinsic function tables in this chapter.
•
The abbreviation
DOUBLE
stands for
DOUBLE PRECISION
.
•
An intrinsic that takes an
INTEGER
argument accepts
INTEGER*2
,
INTEGER*4
, or
INTEGER*8
.
•
An intrinsic that returns an
INTEGER
value returns the prevailing
INTEGER type: if no
-i2
or
-dbl
, then
INTEGER*4
; if
-i2
, then
INTEGER*4
; if
-dbl
, then
INTEGER*8
.
The exceptions are
LOC
and
MALLOC
, which always return an
INTEGER*4
.
•
(SPARC only) An intrinsic that returns a
REAL
value returns the prevailing
REAL
type: if no
-r8
, then
REAL*4
; if
-r8
, then
REAL*8
.
•
(SPARC only) An intrinsic that returns a
DOUBLE PRECISION
value returns the prevailing
DOUBLE PRECISION
type: if no
-r8
, then
REAL*8
; if
-r8 then
REAL*16
.
•
(SPARC only) An intrinsic that returns a
COMPLEX
value returns the prevailing
COMPLEX
type: if no
-r8
, then
COMPLEX*8
; if
-r8
, then
COMPLEX*16
.
Intrinsic Functions
327
328
6
•
(SPARC only) An intrinsic that returns a
DOUBLE COMPLEX
value returns the prevailing
DOUBLE COMPLEX
type: if no
-r8
, then
COMPLEX*16
; if
-r8
, then
COMPLEX*32
.
•
A function with a generic name returns a value with the same type as the argument—except for type conversion functions, the nearest integer function, and the absolute value of a complex argument. If there is more than one argument, they must all be of the same type.
•
If a function name is used as an actual argument, then it must be a specific name.
•
If a function name is used as a dummy argument, then it does not identify an intrinsic function in the subprogram, and it has a data type according to the same rules as for variables and arrays.
6.5 Notes on Functions
Tables and notes 1 through 12 are based on the “Table of Intrinsic Functions,” from ANSI X3.9-1978 Programming Language FORTRAN, with the FORTRAN 77 extensions added.
(1)
INT
If
A
is type integer, then
INT(A)
is
A
.
If
A
is type real or double precision, then: if
|A| < 1
, then
INT(A)
is 0 if
|A|
≥
1
, then
INT(A)
is the greatest integer that does not exceed the magnitude of
A
, and whose sign is the same as the sign of
A
. (Such a mathematical integer value may be too large to fit in the computer integer type.)
If
A
is type complex or double complex, then apply the above rule to the real part of
A
.
If
A
is type real, then
IFIX(A)
is the same as
INT(A)
.
(2)
REAL
If
A
is type real, then
REAL(A)
is
A
.
If
A
is type integer or double precision, then
REAL(A)
is as much precision of the significant part of
A
as a real datum can contain.
FORTRAN 77 Reference Manual
6
If
A
is type complex, then
REAL(A)
is the real part of
A
.
If
A
is type double complex, then
REAL(A)
is as much precision of the significant part of the real part of
A
as a real datum can contain.
(3)
DBLE
If
A
is type double precision, then
DBLE(A)
is
A
.
If
A
is type integer or real, then
DBLE(A)
is as much precision of the significant part of
A
as a double precision datum can contain.
If
A
is type complex, then
DBLE(A)
is as much precision of the significant part of the real part of
A
as a double precision datum can contain.
If
A
is type
COMPLEX*16
, then
DBLE(A)
is the real part of
A
.
(3’)
QREAL
If
A
is type
REAL*16
, then
QREAL(A)
is
A
.
If
A
is type integer, real, or double precision, then
QREAL(A)
is as much precision of the significant part of
A
as a
REAL*16
datum can contain.
If
A
is type complex or double complex, then
QREAL(A)
is as much precision of the significant part of the real part of
A
as a
REAL*16
datum can contain.
If
A
is type
COMPLEX*16
or
COMPLEX*32
, then
QREAL(A)
is the real part of
A
.
(4)
CMPLX
If
A
is type complex, then
CMPLX(A)
is
A
.
If
A
is type integer, real, or double precision, then
CMPLX(A)
is
REAL(A) + 0i
.
If
A1 and A2
are type integer, real, or double precision, then
CMPLX(A1,A2) is
REAL(A1) + REAL(A2)*i
.
If
A
is type double complex, then
CMPLX(A)
is
REAL( DBLE(A) ) + i*REAL( DIMAG(A) )
.
If
CMPLX
has two arguments, then they must be of the same type, and they may be one of integer, real, or double precision.
Intrinsic Functions
329
6
330
If
CMPLX
has one argument, then it may be one of integer, real, double precision, complex,
COMPLEX*
16, or
COMPLEX*32
.
(4’)
DCMPLX
If
A
is type
COMPLEX
*16, then
DCMPLX(A)
is
A
.
If
A
is type integer, real, or double precision, then
DCMPLX(A)
is
DBLE(A) + 0i
.
If
A1
and
A2
are type integer, real, or double precision, then
DCMPLX(A1,A2)
is
DBLE(A1) + DBLE(A2)*i
.
If
DCMPLX
has two arguments, then they must be of the same type, and they may be one of integer, real, or double precision.
If
DCMPLX
has one argument, then it may be one of integer, real, double precision, complex,
COMPLEX
*16, or
COMPLEX*32
.
(5)
ICHAR
ICHAR(A)
is the position of
A
in the collating sequence.
The first position is 0, the last is
N-1, 0
≤
ICHAR(A)
≤
N-1
, where
N
is the number of characters in the collating sequence, and
A
is of type character of length one.
CHAR
and
ICHAR
are inverses in the following sense:
•
ICHAR(CHAR(I)) = I
, for
0
≤
I
≤
N-1
•
CHAR(ICHAR(C)) = C
, for any character
C
capable of representation in the processor
(6)
COMPLEX
A
COMPLEX
value is expressed as an ordered pair of reals,
(ar, ai)
, where ar
is the real part, and ai
is the imaginary part.
(7) Radians
All angles are expressed in radians, unless the “Intrinsic Function” column includes the “(degrees)” remark.
(8)
COMPLEX
Function
The result of a function of type
COMPLEX
is the principal value.
FORTRAN 77 Reference Manual
6
(8’)
CBRT
If a
is of
COMPLEX
type,
CBRT
results in
COMPLEX RT1=(A, B)
, where:
A>= 0.0
, and -60 degrees
<= arctan (B/A) < +
60 degrees.
Other two possible results can be evaluated as follows:
•
RT2 = RT1 * (-0.5, square_root (0.75))
•
RT3 = RT1 * (-0.5, square_root (0.75))
(9) Argument types
All arguments in an intrinsic function reference must be of the same type.
(10)
INDEX
INDEX(X,Y)
is the place in
X where
Y
starts. That is, it is the starting position within character string
X
of the first occurrence of character string
Y
.
If
Y
does not occur in
X
, then
INDEX(X,Y)
is 0.
If
LEN(X) < LEN(Y)
, then
INDEX(X,Y)
is 0.
(11) Argument to
LEN
The value of the argument of the
LEN
function need not be defined at the time the function reference is executed.
(12) Lexical Compare
LGE( X, Y )
is true if
X=Y
, or if
X
follows
Y
in the collating sequence; otherwise, it is false.
LGT( X, Y )
is true if
X
follows
Y
in the collating sequence; otherwise, it is false.
LLE( X, Y )
is true if
X=Y
, or if
X
precedes
Y
in the collating sequence; otherwise, it is false.
LLT( X, Y )
is true if
X
precedes
Y
in the collating sequence; otherwise, it is false.
If the operands for
LGE
,
LGT
,
LLE
, and
LLT
are of unequal length, the shorter operand is considered as if it were extended on the right with blanks.
Intrinsic Functions
331
332
6
(13) Bit Functions
See Chapter 8, “VMS Language Extensions,” for details on other bitwise operations. ♦
(14) Shift
LSHIFT
shifts a1 logically left by a2 bits (inline code).
LRSHFT
shifts a1 logically right by a2 bits (inline code).
RSHIFT
shifts a1 arithmetically right by a2 bits.
ISHFT
shifts a1 logically left if a2 > 0 and right if a2 < 0.
The
LSHIFT
and
RSHIFT
functions are the FORTRAN 77 analogs of the C
<<
and
>>
operators. As in C, the semantics depend on the hardware.
(15) Environmental inquiries
Only the type of the argument is significant.
(16) Epsilon
Epsilon is the least e
, such that
1.0 + e
≠
1.0
.
(17)
LOC
and
MALLOC
The
LOC
function returns the 32-bit address of a variable or of an external procedure. The function call
MALLOC(
n
)
allocates a block of at least n bytes, and returns the 32-bit address of that block.
(18)
SIZEOF
The
SIZEOF
intrinsic cannot be applied to arrays of an assumed size, characters of a length that is passed, or subroutine calls or names.
6.6 VMS Intrinsic Functions
This section lists VMS FORTRAN intrinsic routines recognized by f77
. They are, of course, nonstandard. ♦
FORTRAN 77 Reference Manual
Name
CDABS
CDEXP
CDLOG
CDSQRT
CDSIN
CDCOS
DCMPLX
DCONJG
DIMAG
DREAL
Name
SIND
SIND
DSIND
QSIND
COSD
COSD
DCOSD
QCOSD
TAND
TAND
DTAND
QTAND
ASIND
ASIND
DASIND
QASIND
Double-Precision Complex
Table 6-10 Double-Precision Complex Functions
Generic/Specific Function
Specific
Specific
Specific
Specific
Specific
Specific
Absolute value
Exponential, e**a
Natural log
Square root
Sine
Cosine
Generic
Specific
Specific
Specific
Convert to
DOUBLE COMPLEX
Complex conjugate
Imaginary part of complex
Real part of complex
Argument Type
COMPLEX*16
COMPLEX*16
COMPLEX*16
COMPLEX*16
COMPLEX*16
COMPLEX*16
Any numeric
COMPLEX*16
COMPLEX*16
COMPLEX*16
Degree-Based Trigonometric
Table 6-11 Degree-Based Trigonometric Functions
Generic/Specific Function
Generic
Specific
Specific
Specific
Generic
Specific
Specific
Specific
Generic
Specific
Specific
Specific
Generic
Specific
Specific
Specific
Sine
Sine
Sine
Sine
Cosine
Cosine
Cosine
Cosine
Tangent
Tangent
Tangent
Tangent
Arc sine
Arc sine
Arc sine
Arc sine
Argument Type
-
REAL*4
REAL*8
REAL*16
-
REAL*4
REAL*8
REAL*16
-
REAL*4
REAL*8
REAL*16
-
REAL*4
REAL*8
REAL*16
Result Type
-
REAL*4
REAL*8
REAL*16
-
REAL*4
REAL*8
REAL*16
-
REAL*4
REAL*8
REAL*16
-
REAL*4
REAL*8
REAL*16
Result Type
REAL*8
COMPLEX*16
COMPLEX*16
COMPLEX*16
COMPLEX*16
COMPLEX*16
COMPLEX*16
COMPLEX*16
REAL*8
REAL*8
6
Intrinsic Functions
333
6
Name
ACOSD
ACOSD
DACOSD
QACOSD
ATAND
ATAND
DATAND
QATAND
ATAN2D
ATAN2D
DATAN2D
QATAN2D
Name
IBITS
IIBITS
JIBITS
ISHFT
IISHFT
JISHFT
ISHFTC
IISHFTC
JISHFTC
IAND
IIAND
JIAND
IOR
IIOR
JIOR
IEOR
IIEOR
JIEOR
Table 6-11 Degree-Based Trigonometric Functions (Continued)
Generic/Specific Function
Generic
Specific
Specific
Specific
Arc cosine
Arc cosine
Arc cosine
Arc cosine
Generic
Specific
Specific
Specific
Generic
Specific
Specific
Specific
Arc tangent
Arc tangent
Arc tangent
Arc tangent
Arc tangent of a1/a2
Arc tangent of a1/a2
Arc tangent of a1/a2
Arc tangent of a1/a2
Argument Type
-
REAL*4
REAL*8
REAL*16
-
REAL*4
REAL*8
REAL*16
-
REAL*4
REAL*8
REAL*16
Result Type
-
REAL*4
REAL*8
REAL*16
-
REAL*4
REAL*8
REAL*16
-
REAL*4
REAL*8
REAL*16
Bit-Manipulation
Table 6-12 Bit-Manipulation Functions
Generic/Specific Function
Generic
Specific
Specific
Generic
Specific
Specific
Generic
Specific
Specific
Generic
Specific
Specific
Generic
Specific
Specific
Generic
Specific
Specific
From a1
, initial bit a2
, extract a3
bits
From a1
, initial bit a2
, extract a3
bits
From a1
, initial bit a2
, extract a3
bits
Shift a1
logically by a2
bits *
Shift a1
logically left by a2
bits
Shift a1
logically left by a2
bits
In a1
, circular shift by a2
places, of right a3
bits
In a1
, circular shift by a2
places, of right a3
bits
In a1
, circular shift by a2
places, of right a3
bits
Bitwise
AND
of a1
, a2
Bitwise
AND
of a1
, a2
Bitwise
AND
of a1
, a2
Bitwise
OR
of a1
, a2
Bitwise
OR
of a1
, a2
Bitwise
OR
of a1
, a2
Bitwise exclusive
OR
of a1
, a2
Bitwise exclusive
OR
of a1
, a2
Bitwise exclusive
OR
of a1
, a2
Argument Type Result Type
-
INTEGER*2
INTEGER*4
-
INTEGER*2
INTEGER*4
-
INTEGER*2
INTEGER*4
-
INTEGER*2
INTEGER*4
-
INTEGER*2
INTEGER*4
-
INTEGER*2
INTEGER*4
-
INTEGER*2
INTEGER*4
-
INTEGER*2
INTEGER*4
-
INTEGER*2
INTEGER*4
-
INTEGER*2
INTEGER*4
-
INTEGER*2
INTEGER*4
-
INTEGER*2
INTEGER*4
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FORTRAN 77 Reference Manual
6
Name
IIABS
JIABS
IMAX0
JMAX0
IMIN0
JMIN0
Name
NOT
INOT
JNOT
IBSET
IIBSET
JIBSET
BTEST
BITEST
BJTEST
IBCLR
IIBCLR
JIBCLR
Table 6-12 Bit-Manipulation Functions (Continued)
Generic/Specific Function
Generic
Specific
Specific
Bitwise complement
Bitwise complement
Bitwise complement
Generic
Specific
Specific
Generic
Specific
Specific
Generic
Specific
Specific
In
In
In a1 a1 a1
, set bit
, set bit
, set bit a2 a2 a2
to 1
to 1; return new
to 1; return new a1 a1
If bit a2
of a1
is 1, return
.TRUE.
If bit a2
of a1
is 1, return
.TRUE.
If bit a2
of a1
is 1, return
.TRUE.
In a1
, set bit a2
to 0; return new a1
In a1
, set bit a2
to 0; return new a1
In a1
, set bit a2
to 0; return new a1
Argument Type Result Type
-
INTEGER*2
INTEGER*4
-
INTEGER*2
INTEGER*4
-
INTEGER*2
INTEGER*4
-
INTEGER*2
INTEGER*4
-
INTEGER*2
INTEGER*4
-
INTEGER*2
INTEGER*4
-
INTEGER*2
INTEGER*4
-
INTEGER*2
INTEGER*4
*
ISHFT
—If a2
is positive, then shift left; if negative, then shift right.
Multiple Integer Types
The possibility of multiple integer types is not addressed by the FORTRAN 77
Standard.
f77
copes with their existence by treating a specific
INTEGER
→
INTEGER
function name (
IABS
, and so forth) as a special sort of generic. The argument type is used to select the appropriate runtime routine name, which is not accessible to the programmer.
VMS FORTRAN 77 takes a similar approach, but makes the specific names available.
Generic/Specific
Specific
Specific
Specific
Specific
Specific
Specific
Table 6-13 Integer Functions
Function
Absolute value
Absolute value
Maximum
1
Maximum
1
Minimum
Minimum
1
1
Argument Type
INTEGER*2
INTEGER*4
INTEGER*2
INTEGER*4
INTEGER*2
INTEGER*4
Result Type
INTEGER*2
INTEGER*4
INTEGER*2
INTEGER*4
INTEGER*2
INTEGER*4
Intrinsic Functions
335
6
Name
IINT
JINT
IIDINT
JIDINT
IQINT
IIQINT
JIQINT
ININT
JNINT
IIDNNT
JIDNNT
IQNINT
IIQNNT
JIQNNT
IIFIX
JIFIX
IMAX1
JMAX1
Name
IIDIM
JIDIM
Generic/Specific
Specific
Specific
IMOD
JMOD
IISIGN
JISIGN
Specific
Specific
Specific
Specific
1. There must be at least two arguments.
2. The positive difference is: a1-min(a1,a2))
Table 6-13 Integer Functions (Continued)
Function
Positive difference
Positive difference
2
2
Remainder of a1/a2
Remainder of a1/a2
Transfer of sign, |a1|* sign(a2)
Transfer of sign, |a1|* sign(a2)
Argument Type
INTEGER*2
INTEGER*4
INTEGER*2
INTEGER*4
INTEGER*2
INTEGER*4
Result Type
INTEGER*2
INTEGER*4
INTEGER*2
INTEGER*4
INTEGER*2
INTEGER*4
Functions Coerced to a Particular Type
Some VMS FORTRAN functions coerce to a particular
INTEGER
type.
Specific
Specific
Generic
Specific
Specific
Specific
Specific
Specific
Specific
Generic/Specific
Specific
Specific
Specific
Specific
Specific
Specific
Specific
Specific
Specific
Table 6-14 Translated Functions that VMS Coerces to a Particular Type
Function
Truncation toward zero
Truncation toward zero
Truncation toward zero
Truncation toward zero
Truncation toward zero
Truncation toward zero
Truncation toward zero
Nearest integer,
INT(a+.5*sign(a))
Nearest integer,
INT(a+.5*sign(a))
Nearest integer,
INT(a+.5*sign(a))
Nearest integer,
INT(a+.5*sign(a))
Nearest integer,
INT(a+.5*sign(a))
Nearest integer,
INT(a+.5*sign(a))
Nearest integer,
INT(a+.5*sign(a))
Fix
Fix
Maximum
1
Maximum
1
Argument Type
REAL*4
REAL*4
REAL*8
REAL*8
REAL*16
REAL*16
REAL*16
REAL*4
REAL*4
REAL*8
REAL*8
REAL*16
REAL*16
REAL*16
REAL*4
REAL*4
REAL*4
REAL*4
Result Type
INTEGER*2
INTEGER*4
INTEGER*2
INTEGER*4
INTEGER
INTEGER*2
INTEGER*4
INTEGER*2
INTEGER*4
INTEGER*2
INTEGER*4
INTEGER
INTEGER*2
INTEGER*4
INTEGER*2
INTEGER*4
INTEGER*2
INTEGER*4
336
FORTRAN 77 Reference Manual
6
Name
FLOATI
FLOATJ
DFLOAT
DFLOTI
DFLOTJ
AIMAX0
AJMAX0
AIMIN0
AJMIN0
Name
IMIN1
JMIN1
Generic/Specific
Specific
Specific
Table 6-14 Translated Functions that VMS Coerces to a Particular Type (Continued)
Function
Minimum
1
Minimum
1
Argument Type
READ*4
READ*4
Result Type
INTEGER*2
INTEGER*4
1. There must be at least two arguments.
REAL*16
is SPARC only.
Functions Translated to a Generic Name
In some cases, each VMS-specific name is translated into an f77
generic name.
Table 6-15 VMS Functions That Are Translated into f77
Generic Names
Generic/Specific
Specific
Specific
Generic
Specific
Specific
Specific
Specific
Specific
Specific
Function
Convert to
REAL*4
Convert to
REAL*4
Convert to
REAL*8
Convert to
REAL*8
Convert to
REAL*8
Maximum
Maximum
Minimum
Minimum
Argument Type
INTEGER*2
INTEGER*4
INTEGER
INTEGER*2
INTEGER*4
INTEGER*2
INTEGER*4
INTEGER*2
INTEGER*4
Result Type
REAL*4
REAL*4
REAL*8
REAL*8
REAL*8
REAL*4
REAL*4
REAL*4
REAL*4
Intrinsic Functions
337
6
Name
ZEXT
IZEXT
JZEXT
Zero Extend
The following zero-extend functions are recognized by f77
. The first unused high-order bit is set to zero and extended toward the higher-order end to the width indicated in the table
Generic/Specific
Generic
Specific
Specific
Table 6-16 Zero-Extend Functions
Function
Zero-extend
Zero-extend
Zero-extend
Argument Type
-
BYTE
LOGICAL*1
LOGICAL*2 INTEGER*2
BYTE
LOGICAL*1 LOGICAL*2
LOGICAL*4
INTEGER
INTEGER*2
INTEGER*4
Result Type
-
INTEGER*2
INTEGER*4
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FORTRAN 77 Reference Manual
FORTRAN 77 Library Routines
7
This chapter lists the f77
library routines alphabetically, along with explanations and examples. See Chapter 6, “Intrinsic Functions,” for VMS intrinsic functions.
7.1
abort
: Terminate and Write Memory to Core File
The subroutine is: call abort abort
cleans up the I/O buffers and then aborts producing a core
file in the current directory. See also abort
(3).
7.2
access
: Check File for Permissions or Existence
The function is: status = access (
name, mode
)
name
character
Input
mode
Return value character
INTEGER
Input
Output
File name
Permissions
status=0: OK
status>0: Error code
339
340
7
access
tells you if you can access the file name with the permissions mode.
You can set mode to one or more of r, w,
or x, in
any order, and in any combination, where r, w, x
have the following meanings: r w x blank
Read
Write
Execute
Existence
Example 1: Write, and arguments are literals: integer access, status status = access ( 'taccess.data', 'w' ) if ( status .eq. 0 ) write(*,*) "ok" if ( status .ne. 0 ) write(*,*) 'cannot write', status end
Example 2: Test for existence: integer access, status status = access ( 'taccess.data', ' ' )! blank mode if ( status .eq. 0 ) write(*,*) "ok" if ( status .ne. 0 ) write(*,*) 'no such file', status end
See also access
(2) and perror
(3F).
7.3
alarm
: Execute a Subroutine after a Specified Time
The function is: n = alarm (
time
,
sbrtn
)
time sbrtn
INTEGER
Routine name
Input
Input
Return value
INTEGER
Output
Number of seconds to wait (0=do not call)
Subprogram to execute must be listed in an external statement.
Time remaining on the last alarm
FORTRAN 77 Reference Manual
7
Example: alarm
—wait 9 seconds then call sbrtn
: integer alarm, time / 1 / common / alarmcom / i external sbrtn i = 9 write(*,*) i nseconds = alarm ( time, sbrtn ) do n = 1,100000 ! Wait until alarm activates sbrtn.
r = n ! (any calculations that take enough time) x=sqrt(r) end do write(*,*) i end subroutine sbrtn common / alarmcom / i i = 3 return
! Do no I/O in this routine.
end
See also: alarm
(3C), sleep
(3F), and signal
(3F).
Note the following restrictions:
•
A subroutine cannot pass its own name to alarm
because of restrictions in the FORTRAN 77 Standard.
•
Your subroutine must not do any I/O because the alarm
routine generates signals, and signals interfere with any I/O. I/O is interrupt-driven.
•
Do not call alarm()
from a FORTRAN 77 MP program—it has unpredictable behavior in MP mode.
FORTRAN 77 Library Routines
341
7
7.4
bit
: Bit Functions:
and
,
or
, …,
bit
,
setbit
, …
The definitions are: and(
word1, word2
) or(
word1, word2
) xor(
word1, word2
) not(
word
) lshift(
word, nbits
) rshift(
word, nbits
) bis(
bitnum
,
word
) bic(
bitnum
,
word
)
Computes the bitwise and of its arguments.
Computes the bitwise inclusive or of its arguments.
Computes the bitwise exclusive or of its arguments.
Returns the bitwise complement of its argument.
Is a logical left shift with no end around carry.
Is an arithmetic right shift with sign extension.
Sets bit bitnum in word to 1.
Clears bit bitnum in word to 0.
bit(
bitnum
,
word
)
Tests bit bitnum in word and returns
.true.
if the bit is 1,
.false.
if it is 0.
setbit(
bitnum
,
word
,
state
)
Sets bit bitnum in word to 1 if state is nonzero, and clears it otherwise.
The alternate external versions for MIL-STD-1753 are: iand(
m
,
n
) ior(
m
,
n
) ieor(
m
,
n
) ishft(
m
,
k
) ishftc(
m
,
k
,
ic
) ibits(
m
,
i
,
len
) ibset(
m
,
i
) ibclr(
m
,
i
) btest(
m
,
i
)
Computes the bitwise and of its arguments.
Computes the bitwise inclusive or of its arguments.
Computes the bitwise exclusive or of its arguments.
Is a logical shift with no end around carry (left if k>0, right if k<0).
Circular shift: right-most ic bits of m are left-shifted circularly k places.
Extracts bits: from m, starting at bit i, extracts len bits.
Sets bit: return value is equal to word m with bit number i set to 1.
Clears bit: return value is equal to word m with bit number i set to 0.
Tests bit i in m; returns
.true.
if the bit is 1, and
.false.
if it is 0.
See also “mvbits: Move a Bit Field,” on page 395, and “Miscellaneous
Functions,” on page 325.
342
FORTRAN 77 Reference Manual
Usage:
and
,
or
,
xor
,
not
,
rshift
,
lshift
x
= and(
word1, word2
)
x
= or(
word1, word2
)
x
= xor(
word1, word2
)
x
= not(
word
)
x
= rshift(
word, nbits
)
x
= lshift(
word, nbits
)
word1, word2, word, nbits integer
or logical
(short or long) Input
These are generic functions expanded inline by the compiler.
No test is made for a reasonable value of nbits.
Example: and, or, xor, not
: print 1, and(7,4), or(7,4), xor(7,4), not(4)
1 format(4x 'and(7,4)', 5x 'or(7,4)', 4x 'xor(7,4)',
& 6x 'not(4)'/4o12.11) end demo% f77 -silent tandornot.f demo% a.out
and(7,4) or(7,4) xor(7,4) not(4)
00000000004 00000000007 00000000003 37777777773 demo%
Example: lshift
, rshift
: integer lshift, rshift print 1, lshift(7,1), rshift(4,1)
1 format(1x 'lshift(7,1)', 1x 'rshift(4,1)'/2o12.11) end demo% f77 -silent tlrshift.f demo% a.out
lshift(7,1) rshift(4,1)
00000000016 00000000002 demo%
7
FORTRAN 77 Library Routines
343
7
Usage:
bic
,
bis
,
bit
,
setbit
call bic(
bitnum
,
word
) call bis(
bitnum
,
word
) call setbit(
bitnum
,
word
,
state
)
x
= bit(
bitnum
,
word
)
Return value logical
bitnum state word
INTEGER*4
INTEGER*4
INTEGER*4
Logical value
Input
Input
Input and output (an input that is changed)
Bits are numbered so that bit 0 is the least significant bit, and bit 31 is the most significant.
bic
, bis
, and setbit
are external subroutines.
bit
is an external function.
344
FORTRAN 77 Reference Manual
Example 3: bic
, bis
, setbit
, bit
: integer bitnum/2/, state/0/, word/7/ logical bit print 1, word
1 format(13x 'word', o12.11) call bic( bitnum, word ) print 2, word
2 format('after bic(2,word)', o12.11) call bis( bitnum, word ) print 3, word
3 format('after bis(2,word)', o12.11) call setbit( bitnum, word, state ) print 4, word
4 format('after setbit(2,word,0)', o12.11) print 5, bit(bitnum, word)
5 format('bit(2,word)', L ) end
<
output
>
word 00000000007 after bic(2,word) 00000000003 after bis(2,word) 00000000007 after setbit(2,word,0) 00000000003 bit(2,word) F
7.5
chdir
: Change Default Directory
The function is:
n
= chdir(
dirname
)
dirname
Return value character
INTEGER
Input
Output
Example: chdir
—change cwd
to
MyDir
:
Directory name
n=0: OK, n>0: Error code integer chdir, n n = chdir ( 'MyDir' ) if ( n .ne. 0 ) stop 'chdir: error' end
7
FORTRAN 77 Library Routines
345
346
7
See also: chdir
(2), cd
(1), and perror
(3F).
Path names can be no longer than
MAXPATHLEN
as defined in
<sys/param.h>
.
Use of this function can cause inquire by unit to fail.
Certain FORTRAN 77 file operations reopen files by name. Using chdir
while doing I/O can cause the runtime system to lose track of files created with relative path names. including the files that are created by open
statements without file names.
7.6
chmod
: Change the Mode of a File
The function is:
n
= chmod(
name
,
mode
)
name mode
character character
Input
Input
Single path name
Anything recognized by chmod
(1), such as o-w
,
444
, etc.
Output n = 0: OK; n>0: System error number Return value
INTEGER
Example: chmod
—add write permissions to
MyFile
.: character*18 name, mode integer chmod, n name = 'MyFile' mode = '+w' n = chmod( name, mode ) if ( n .ne. 0 ) stop ’chmod: error’ end
See also: chmod
(1). Note this bug: the path names cannot be longer than
MAXPATHLEN
as defined in
<sys/param.h>
.
FORTRAN 77 Reference Manual
7
7.7
date
: Get Current System Date as a Character String
call date(
c
)
c
CHARACTER*
9 Output Variable, array, array element, or character substring
The form of the returned string c is:
dd-mmm-yy dd
Day of the month, as a 2-digit integer
mmm yy
Month, as a 3-letter abbreviation
Year, as a 2-digit integer
Example: date
: demo% cat dat1.f
* dat1.f -- Get the date as a character string.
character c*9 call date ( c ) write(*,"(' The date today is: ', A9 )" ) c end demo% f77 -silent dat1.f demo% a.out
The date today is: 23-Sep-88 demo%
See also Section 7.27, “idate: Return Current System Date.”
7.8
dtime
,
etime
: Elapsed Execution Time
Both functions have return values of elapsed time (or -1.0 as error indicator).
The time is in seconds. The resolution is to a nanosecond under Solaris 2.x, and is determined by the system clock frequency under Solaris 1.x.
dtime
: Elapsed Time Since the Last
dtime
Call
For dtime
, the elapsed time is:
•
First call: elapsed time since start of execution
FORTRAN 77 Library Routines
347
7
348
•
Subsequent calls: elapsed time since the last call to dtime
•
Single processor: time used by the CPU
•
Multiple Processor: the sum of times for all the CPUs, which is not useful data; use etime
instead.
Note –
Do not call dtime
from within a parallelized loop.
The function is:
e
= dtime(
tarray
)
tarray
real(2)
Output e= -1.0:
e
≠
-1.0:
Return value real
Output e= -1.0:
e
≠
-1.0:
Example: dtime()
, single processor:
Error: tarray values are undefined
User time in tarray(1) if no error
System time in tarray(2) if no error
Error
The sum of tarray(1) and tarray(2) real e, dtime, t(2) print *, 'elapsed:', e, ', user:', t(1), ', sys:', t(2) do i = 1, 10000 k=k+1 end do e = dtime( t ) print *, 'elapsed:', e, ', user:', t(1), ', sys:', t(2) end demo% f77 -silent tdtime.f demo% a.out elapsed: 0., user: 0., sys: 0.
elapsed: 0.180000, user: 6.00000E-02, sys: 0.120000
demo%
etime
: Elapsed Time Since Start of Execution
For etime
, the elapsed time is:
•
Single Processor—CPU time for the calling process
•
Multiple Processor—wallclock time while processing your program
FORTRAN 77 Reference Manual
7
Here is how FORTRAN 77 decides single processor or multiple processor:
For a FORTRAN 77 MP program that uses an MP option—ultimately, linked with libF77_mt
, if the environment variable
PARALLEL
is:
•
Undefined, the current run is single processor.
•
Defined and in the range 1, 2, 3, …, the current run is multiple processor.
•
Defined, but some value other than 1, 2, 3, …, the results are unpredictable.
The function is:
e
= etime(
tarray
)
tarray
real(2)
Output
Return value real
Output
e= -1.0:
e
≠
-1.0:
e= -1.0:
e
≠
-1.0:
Error: tarray values are undefined
Single Processor: User time in
System time in
Multiple Processor: Wall clock time in
0.0 in
Error
The sum of tarray(1) and tarray(2)
Example: etime()
, single processor:
tarray(1) tarray(2) tarray(1) tarray(2)
real e, etime, t(2) do i = 1, 10000 k=k+1 end do e = etime( t ) print *, 'elapsed:', e, ', user:', t(1), ‘, sys:', t(2) end demo% f77 -silent tetime.f demo% a.out elapsed: 0.190000, user: 6.00000E-02, sys: 0.130000
demo%
See also times
(2), f77
(1), and the FORTRAN 77 User’s Guide.
FORTRAN 77 Library Routines
349
7
7.9
exit
: Terminate a Process and Set the Status
The subroutine is: call exit(
status
)
status
Example: exit()
:
INTEGER integer status status = 7 call exit( status ) end
Input exit
flushes and closes all the files in the process, and notifies the parent process if it is executing a wait
.
The low-order 8 bits of status are available to the parent process. These 8 bits are shifted left 8 bits, and all other bits are zero. (Therefore, status should be in the range of 256 - 65280). This call will never return.
The C function exit
can cause cleanup actions before the final ' sys exit
'.
If you call exit
without an argument, you will get a warning message, and a zero will be automatically provided as an argument. See also: exit
(2), fork
(2), fork
(3f), wait
(2), wait
(3f).
7.10
f77_floatingpoint
: FORTRAN 77 IEEE Definitions
The file f77_floatingpoint.h
defines constants and types used to implement standard floating-point according to ANSI/IEEE Std 754-1985.
Include the file in a source program as follows:
#include <f77/f77_floatingpoint.h>
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The file f77_floatingpoint.h
defines constants and types used to implement standard floating-point according to ANSI/IEEE Std 754-1985. Use these constants and types to write more easily understood
.F
source files that will undergo automatic preprocessing prior to FORTRAN 77 compilation.
IEEE Rounding Mode
fp_direction_type
The type of the IEEE rounding direction mode. The order of enumeration varies according to hardware.
SIGFPE Handling
sigfpe_code_type sigfpe_handler_type
SIGFPE_DEFAULT
SIGFPE_IGNORE
SIGFPE_ABORT
The type of a
SIGFPE
code.
The type of a user-definable
SIGFPE
exception handler called to handle a particular
SIGFPE
code.
A macro indicating default
SIGFPE
exception handling: IEEE exceptions to continue with a default result and to abort for other
SIGFPE
codes.
A macro indicating an alternate
SIGFPE
exception handling, namely to ignore and continue execution.
A macro indicating an alternate
SIGFPE
exception handling, namely to abort with a core dump.
FORTRAN 77 Library Routines
351
7
IEEE Exception Handling
N_IEEE_EXCEPTION
The number of distinct IEEE floating-point exceptions.
fp_exception_type
The type of the
N_IEEE_EXCEPTION
exceptions. Each exception is given a bit number.
fp_exception_field_type
The type intended to hold at least
N_IEEE_EXCEPTION
bits corresponding to the IEEE exceptions numbered by fp_exception_type
. Thus, fp_inexact
corresponds to the least significant bit and fp_invalid
to the fifth least significant bit.
Some operations can set more than one exception.
IEEE Classification
fp_class_type
A list of the classes of IEEE floating-point values and symbols.
Refer to the Numerical Computation Guide. See also ieee_environment
(3M) and f77_ieee_environment
(3F).
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7.11
f77_ieee_environment
: IEEE Arithmetic
Here is a summary: ieee_flags
ieeer
= ieee_flags(
action
,
mode
,
in
,
out
) ieee_handler ieeer = ieee_handler(
action
,
exception
,
hdl
) sigfpe
action
ieeer = sigfpe(
code
,
hdl
) character
Input
code mode in exception
sigfpe_code_type character character character
Input
Input
Input
Input
hdl out
Return value sigfpe_handler_type character
INTEGER
Input
Output
Output
These subprograms provide modes and status required to fully exploit
ANSI/IEEE Std 754-1985 arithmetic in a FORTRAN 77 program. They correspond closely to the functions ieee_flags
(3M
)
, ieee_handler
(3M), and sigfpe
(3).
If you use sigfpe
, you must do your own setting of the corresponding trapenable-mask bits in the floating-point status register. The details are in the
SPARC architecture manual. The libm
function ieee_handler
sets these trap-enable-mask bits for you.
Example 1: Set rounding direction to round toward zero, unless the hardware does not support directed rounding modes: integer ieeer character*1 mode, out, in ieeer = ieee_flags( 'set', 'direction', 'tozero', out )
FORTRAN 77 Library Routines
353
7
Example 2: Clear rounding direction to default (round toward nearest): character*1 out, in ieeer = ieee_flags('clear','direction', in, out )
Example 3: Clear all accrued exception-occurred bits: character*18 out ieeer = ieee_flags( 'clear', 'exception', 'all', out )
Example 4: If Example 3 generates the overflow exception, detect it as follows: character*18 out ieeer = ieee_flags( 'get', 'exception', 'overflow', out )
The above code sets out
to overflow
and ieeer
to 25. Similar coding detects exceptions, such as invalid
or inexact
.
354
FORTRAN 77 Reference Manual
Example 5: hand1.f
, write and use a signal handler (Solaris 2.x): external hand real r / 14.2 /, s / 0.0 / i = ieee_handler( 'set', 'division', hand ) t = r/s end integer function hand ( sig, sip, uap ) integer sig, address structure /fault/ integer address end structure structure /siginfo/ integer si_signo integer si_code integer si_errno record /fault/ fault end structure record /siginfo/ sip address = sip.fault.address
write (*,10) address
10 format('Exception at hex address ', z8 ) end
Read the Numerical Computation Guide. See also: floatingpoint
(3), signal
(3), sigfpe
(3), f77_floatingpoint
(3F), ieee_flags
(3M), and ieee_handler
(3M).
7.12
fdate
: Return Date and Time in an ASCII String
The subroutine or function: call fdate(
string
)
string
character*24
Output
7
FORTRAN 77 Library Routines
355
7
or:
string
= fdate()
Return value character*24
Example 1: fdate
as a subroutine:
Output
If you use it as a function, the calling routine must define the type and length of fdate
.
character*24 string call fdate( string ) write(*,*) string end
Output:
Wed Aug 3 15:30:23 1994
Example 2: fdate
as a function, same output: character*24 fdate write(*,*) fdate() end
See also: ctime
(3), time
(3F), and idate
(3F).
7.13
flush
: Flush Output to a Logical Unit
The subroutine is: call flush(
lunit
)
lunit
INTEGER
Input Logical unit
The flush
subroutine flushes the contents of the buffer for the logical unit, lunit
, to the associated file. This is most useful for logical units 0 and 6 when they are both associated with the control terminal.
See also fclose
(3S).
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FORTRAN 77 Reference Manual
7
7.14
fork
: Create a Copy of the Current Process
The function is:
n
= fork()
Return value
INTEGER
Output n>0: n=Process ID of copy
n<0, n=System error code
The fork
function creates a copy of the calling process. The only distinction between the two processes is that the value returned to one of them, referred to as the parent process, will be the process ID of the copy. The copy is usually referred to as the child
process. The value returned to the child process will be zero.
All logical units open for writing are flushed before the fork to avoid duplication of the contents of I/O buffers in the external files.
Example: fork()
: integer fork, pid pid = fork() end
A corresponding exec
routine has not been provided because there is no satisfactory way to retain open logical units across the exec
routine. However, the usual function of fork/exec
can be performed using system
(3F). See also: fork
(2), wait
(3F), kill
(3F), system
(3F), and perror
(3F).
7.15
free
: Deallocate Memory Allocated by Malloc
The subroutine is: call free (
ptr
)
ptr
pointer
Input free
deallocates a region of memory previously allocated by malloc
. The region of memory is returned to the memory manager; it is not explicitly available to the user’s program.
FORTRAN 77 Library Routines
357
7
Example: free()
: real x pointer ( ptr, x ) ptr = malloc ( 10000 ) call free ( ptr ) end
See Section 7.40, “malloc: Allocate Memory and Get Address,” for details.
7.16
fseek
,
ftell
: Determine Position and Reposition a File
fseek
and ftell
are routines that permit repositioning of a file.
ftell returns a file’s curent position as an offset of so many bytes from the beginning of the file. At some later point in the program, fseek
can use this saved offset value to reposition the file to that same place for reading.
CAUTION: On sequential files, following a call to fseek
by an output operation (e.g. WRITE) causes all data records following the fseek
’ed position to be deleted and replaced by the new data record (and an end-of-file mark).
Rewriting a record in place can only be done with direct access files.
fseek
:
Reposition a File on a Logical Unit
The function is: n = fseek(
lunit
,
offset
,
from
)
lunit offset from
Return value
INTEGER
INTEGER
Input
Input
Open logical unit
Offset in bytes relative to position specified by from
INTEGER
Input 0=Beginning of file
1=Current position
2=End of file
INTEGER
Output n=0: OK; n>0: System error code
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Example: fseek()
—Reposition
MyFile
to two bytes from the beginning: integer fseek, lunit/1/, offset/2/, from/0/, n open( UNIT=lunit, FILE='MyFile' ) n = fseek( lunit, offset, from ) if ( n .gt. 0 ) stop 'fseek error' end
ftell
: Return Current Position of File
The function is:
n
= ftell(
lunit
)
lunit
Return value
INTEGER
INTEGER
Input
Input
Open logical unit
n>=0: n=Offset in bytes from start of file
n<0: n=System error code
Example: ftell()
: integer ftell, lunit/1/, n open( UNIT=lunit, FILE='MyFile' )
* … n = ftell( lunit ) if ( n .lt. 0 ) stop 'ftell error' end
See also fseek
(3S) and perror
(3F).
FORTRAN 77 Library Routines
359
7
7.17
getarg
,
iargc
: Get Command-line Arguments
gettarg
and iargc
return command-line arguments.
getarg
: Get the kth Command-Line Argument
The subroutine is: call getarg(
k
,
arg
)
k
INTEGER
Input
arg
character*
n
Output
n
INTEGER
Size of arg
Index of argument (0=first=command name)
kth argument
Large enough to hold longest argument
iargc
: Get the Count of Command-Line Arguments
The function is:
m
= iargc()
Return value
INTEGER
Output Number of arguments on the command line
Example: iargc
and getarg
, get argument count and each argument: character argv*10 integer i, iargc, n n = iargc() do i = 1, n call getarg( i, argv ) write( *, '( i2, 1x, a )' ) i, argv end do end
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After compiling, a sample run of the above source is: demo% a.out first second last
1 first
2 second
3 last demo%
See also execve
(2) and getenv
(3F).
7.18
getc
,
fgetc
: Get Next Character
getc
and fgetc
get the next character.
getc
: Get Next Character from
stdin
The function is:
status
= getc(
char
)
char
character
Return value
INTEGER
Output
Output
Next character
status=0: OK
status=-1: End of file
status>0: System error code or f77
I/O error code
Example: getc
gets each character from the keyboard; note the Control-D
(EOF): character char integer getc, status status = 0 do while ( status .eq. 0 ) status = getc( char ) write(*, '(i3, o4.3)') status, char end do end
FORTRAN 77 Library Routines
361
362
7
After compiling, a sample run of the above source is: demo% a.out ab
^D
0 141
0 142
0 012
-1 012 demo%
For any logical unit, do not mix normal FORTRAN 77 input with getc()
.
fgetc
: Get Next Character from Specified Logical Unit
The function is:
status
= fgetc(
lunit
,
char
)
lunit char
Return value
INTEGER
INTEGER
Input character
Output
Output
Logical unit
Next character
status=-1: End of File
status>0: System error code or f77
I/O error code
Example: fgetc
gets each character from tfgetc.data
; note the linefeeds
(Octal 012): character char integer fgetc, status open( unit=1, file='tfgetc.data' ) status = 0 do while ( status .eq. 0 ) status = fgetc( 1, char ) write(*, '(i3, o4.3)') status, char end do end
FORTRAN 77 Reference Manual
7
After compiling, a sample run of the above source is: demo% cat tfgetc.data ab yz demo% a.out
0 141
0 142
0 012
0 171
0 172
0 012
-1 012 demo%
For any logical unit, do not mix normal FORTRAN 77 input with fgetc()
.
See also: getc
(3S), intro
(2), and perror
(3F).
7.19
getcwd
: Get Path of Current Working Directory
The function is:
status
= getcwd(
dirname
)
dirname
Return value
n
character*
INTEGER
INTEGER
n
Output
Output
Path name of the current working directory
status=0: OK
status>0: Error code
Size of dirname, in bytes Must be big enough for the longest path name
Example: getcwd
: integer getcwd, status character*64 dirname status = getcwd( dirname ) if ( status .ne. 0 ) stop 'getcwd: error' write(*,*) dirname end
FORTRAN 77 Library Routines
363
7
See also: chdir
(3F), perror
(3F), and getwd
(3).
Note this bug: the path names cannot be longer than
MAXPATHLEN
as defined in
<sys/param.h>
.
7.20
getenv
: Get Value of Environment Variables
The subroutine is: call getenv(
ename
,
evalue
)
ename evalue n
character* character*
INTEGER
n n
Input
Output
Name of the environment variable sought
Value of the environment variable found; blanks if not successful
Size of evalue n must be large enough for the value.
The getenv
subroutine searches the environment list for a string of the form
ename
=
evalue and returns the value in evalue if such a string is present; otherwise, it fills evalue with blanks.
Example: getenv()
: character*18 evalue call getenv( 'SHELL', evalue ) write(*,*) "'", evalue, "'" end
See also: execve
(2) and environ
(5).
7.21
getfd
: Get File Descriptor for External Unit Number
The function is:
fildes
= getfd(
unitn
)
unitn
INTEGER
Return value
INTEGER
Input
Output
External unit number
File descriptor if the file is connected;
-1 if the file is not connected
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Example: getfd()
: integer fildes, getfd, unitn/1/ open( unitn, file='tgetfd.data' ) fildes = getfd( unitn ) if ( fildes .eq. -1 ) stop 'getfd: file not connected' write(*,*) 'file descriptor = ', fildes end
See also open
(2).
7.22
getfilep
: Get File Pointer for External Unit Number
The function is:
irtn
=
c_read
( getfilep(
unitn
),
inbyte
, 1 )
c_read
C function Input You write this C function. See the example.
unitn
INTEGER getfilep INTEGER
Input External unit number.
Return value File pointer if the file is connected; -1 if the file is not connected
This function is used for mixing standard FORTRAN 77 I/O with C I/O. Such a mix is nonportable, and is not guaranteed for subsequent releases of the operating system or FORTRAN 77. Use of this function is not recommended, and no direct interface is provided. You must enter your own C routine to use the value returned by getfilep
. A sample C routine is shown below.
Example: FORTRAN 77 uses getfilep
by passing it to a C function: tgetfilepF.f
character*1 inbyte
integer*4 c_read, getfilep, unitn / 5 /
external getfilep
write(*,'(a,$)') 'What is the digit? '
irtn = c_read( getfilep( unitn ), inbyte, 1 )
write(*,9) inbyte
9 format('The digit read by C is ', a )
end
FORTRAN 77 Library Routines
365
7
tgetfilepC.c
Sample C function actually using getfilep
:
#include <stdio.h> int c_read_ ( fd, buf, nbytes, buf_len )
FILE **fd ; char *buf ; int *nbytes, buf_len ;
{
return fread( buf, 1, *nbytes, *fd ) ;
}
A sample compile-build-run is: demo 11% cc -c tgetfilepC.c demo 12% f77 tgetfilepC.o tgetfilepF.f tgetfileF.f:
MAIN: demo 13% a.out
What is the digit? 3
The digit read by C is 3 demo 14%
For more information, read the chapter on the C-FORTRAN 77 interface in the
FORTRAN 77 4.0 User's Guide. See also open
(2).
7.23
getlog
: Get User’s Login Name
The subroutine is: call getlog(
name
)
name n
character
INTEGER
*n Output User’s login name, or all blanks if the process is running detached from a terminal.
Size of name Large enough to hold the longest name
366
FORTRAN 77 Reference Manual
Example: getlog
: character*18 name call getlog( name ) write(*,*) "'", name, "'" end
See also getlogin
(3).
7.24
getpid
: Get Process ID
The function is:
pid
= getpid()
Return value
INTEGER
Output
Example: getpid
: integer getpid, pid pid = getpid() write(*,*) 'process id = ', pid end
Process ID of the current process
See also getpid
(2).
7.25
getuid
,
getgid
: Get User or Group ID of Process
getuid
and getgid
get the user or group ID of the process, respectively.
getuid
: Get User ID of the Process
The function is:
uid
= getuid()
Return value
INTEGER
Output User ID of the process
7
FORTRAN 77 Library Routines
367
7
getgid
: Get Group ID of the Process
The function is:
gid
= getgid()
Return value
INTEGER
Output Group ID of the process
Example: getuid()
and getpid()
: integer getuid, getgid, gid, uid uid = getuid() gid = getgid() write(*,*) uid, gid end
See also: getuid
(2).
7.26
hostnm
: Get Name of Current Host
The function is:
status
= hostnm(
name
)
name
character*
n
Output
Return value
INTEGER
Output
n
INTEGER
Size of name
Name of current host
status=0: OK
status>0: Error
Big enough to hold the host name, or the memory is clobbered.
Example: hostnm()
: integer hostnm, status character*8 name status = hostnm( name ) write(*,*) 'host name = "', name, '"' end
See also gethostname
(2).
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7
7.27
idate
: Return Current System Date
idate
has two versions:
•
Standard
—Put the current system date into an integer array: day, month, and year.
•
VMS
—Put the current system date into three integer variables: month, day, and year.
If you use the
-lV77
compiler option to request the VMS library, then you get the VMS versions of both time()
and idate()
; otherwise, you get the standard versions.
Standard Version
The standard version puts the current system date into one integer array: day, month, and year.
The subroutine is: call idate(
iarray
)
iarray
INTEGER
Output array
(3). Note the order: day, month, year.
Example: idate
(standard version): integer iarray(3) call idate( iarray ) write(*, "(' The date is: ',3i5)" ) iarray end
Compile and run the above source: demo% f77 -silent tidate.f demo% a.out
The date is: 10 8 1994 demo%
FORTRAN 77 Library Routines
369
7
VMS Version
The VMS version puts the current system date into three integer variables: month, day, and year
The subroutine is:.
call idate(
m
,
d
,
y
)
m d y
INTEGER
INTEGER
INTEGER
Output
Output
Output
Month (1 - 12)
Day (1 - 7)
Year (1 - 99)
Example: idate
(VMS version): integer m, d, y call idate ( m, d, y ) write (*, "(' The date is: ',3i5)" ) m, d, y end
Compile and run the above source; note the
-lV77
option: demo% f77 -silent tidateV.f -lV77 demo% a.out
The date is: 8 10 94 demo%
7.28
itime
: Current System Time
itime
puts the current system time into an integer array: hour, minute, and second.
The subroutine is: call itime(
iarray
)
iarray
INTEGER
Output array
(3). Note the order: hour, minute, second
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FORTRAN 77 Reference Manual
7
Example: itime
: integer iarray(3) call itime( iarray ) write (*, "(' The time is: ',3i5)" ) iarray end
Compile and run the above source: demo% f77 -silent titime.f demo% a.out
The time is: 15 42 35 demo%
See also time
(3f), ctime
(3F), and fdate
(3F).
7.29
index
: Index or Length of Substring
index
has the following forms: index(
a1
,
a2
) rindex(
a1
,
a2
) lnblnk(
a1
) len(
a1
)
Index of first occurrence of string a2 in string a1
Index of last occurrence of string a2 in string a1
Index of last nonblank in string a1
Declared length of string a1
index
: First Occurrence of String a2 in String a1
The intrinsic function is:
n
= index(
a1
,
a2
)
a1 a2
Return value character character
INTEGER
Input
Input
Output
Main string
Substring
n>0: Index of first occurrence of a2 in a1
n=0: a2 does not occur in a1.
FORTRAN 77 Library Routines
371
372
7
rindex
: Last Occurrence of String a2 in String a1
The function is:
n
= rindex(
a1
,
a2
)
a1 a2
Return value character character
INTEGER
Input
Input
Output
Main string
Substring
n>0: Index of last occurrence of a2 in a1
n=0: a2 does not occur in a1
lnblnk
: Last Nonblank in String a1
The function is:
n
= lnblnk(
a1
)
a1
Return value character
INTEGER
Input String
Output n>0: Index of last nonblank in a1
n=0: a1 is all nonblank
len
: Declared Length of String a1
The intrinsic function is:
declen
= len(
a1
)
a1
Return value character
Input
INTEGER
String
Output Declared length of a1
This function is useful since all f77
character objects are of a fixed length and blank-padded.
FORTRAN 77 Reference Manual
Example: len()
, index()
, rindex()
, lnblnk()
:
* 123456789 123456789 1234 character s*24 / 'abcPDQxyz...abcPDQxyz ' / integer declen, index, first, last, len, lnblnk, rindex declen = len( s ) first = index( s, 'abc' ) last = rindex( s, 'abc' ) lastnb = lnblnk( s ) write(*,*) declen, lastnb write(*,*) first, last end demo% f77 -silent tindex.f demo% a.out
32 21
1 13 demo%
In the above example, declen
is 32, not 21.
7.30
inmax
: Return Maximum Positive Integer
The function is:
m
= inmax()
Return value
Example: inmax
:
INTEGER
Output The maximum positive integer integer inmax, m m = inmax() write(*,*) m end demo% f77 -silent tinmax.f demo% a.out
2147483647 demo%
See also libm_single
(3f) and libm_double
(3f).
7
FORTRAN 77 Library Routines
373
7
7.31
ioinit
: Initialize I/O: Carriage Control, File Names, …
The
IOINIT
routine establishes properties of file I/O for files opened after the call to
IOINIT
. The file I/O properties that
IOINIT
controls are as follows:
Carriage control
Blanks/zeroes
File position
Prefix
Recognize carriage control on any logical unit.
Treat blanks in input data fields as blanks or zeroes.
Open files at beginning or at EoF.
Find and open files named prefixNN, 0
≤
NN
≤
19.
IOINIT
does the following:
•
Initializes global parameters specifying f77
file I/O properties
•
Opens logical units 0 through 19 with the specified file I/O properties— attaches externally defined files to logical units at runtime
Duration of File I/O Properties
The file I/O properties apply as long as the connection exists. If you close the unit, the properties no longer apply. The exception is the preassigned units 5 and 6, to which carriage control and blanks/zeroes apply at any time.
Internal Flags
IOINIT
uses labeled common to communicate with the runtime I/O system. It stores internal flags in the equivalent of the following labeled common block:
INTEGER*2 IEOF, ICTL, IBZR
COMMON /_ _IOIFLG/ IEOF, ICTL, IBZR !
Not in user name space
In releases prior to SC 3.0.1, the labeled common block was named
IOIFLG
. We changed this name to
_ _IOIFLG,
so that a user common block named
IOIFLG
does not cause problems. It is safer this way because
_ _IOIFLG
is not part of the user name space.
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FORTRAN 77 Reference Manual
7
Source Code
Some user needs are not satisfied with a generic version of
IOINIT
, so we provide the source code. It is written in FORTRAN 77 77. The location is:
•
For a standard installation, it is in:
/opt/SUNWspro/SC4.0/src/ioinit.f
•
If you installed in
/
mydir, it is in
/
mydir
/SC3.0.1/src/ioinit.f
Usage:
ioinit
call ioinit (
cctl
,
bzro
,
apnd
,
prefix
,
vrbose
)
cctl bzro
logical logical
Input
Input
True: Recognize carriage control, all formatted output (except unit 0)
True: Treat trailing and imbedded blanks as zeroes.
apnd prefix vrbose
logical character* logical
n
Input
Input
Input
True: Open files at EoF. Append.
Nonblank: For unit NN, seek and open file
prefixNN
True: Report ioinit
activity as it happens
See also getarg
(3F) and getenv
(3F).
Restrictions
Note the following restrictions:
•
prefix can be no longer than 30 characters.
•
A path name associated with an environment name can be no longer than
255 characters.
•
The
+
carriage control does not work.
Details of Arguments
Here are the arguments for ioinit
.
FORTRAN 77 Library Routines
375
7
376
cctl (Carriage Control)
By default, carriage control is not recognized on any logical unit. If cctl is
.TRUE.
, then carriage control is recognized on formatted output to all logical units, except unit 0, the diagnostic channel. Otherwise, the default is restored.
bzro (Blanks)
By default, trailing and embedded blanks in input data fields are ignored. If
bzro is
.TRUE.
, then such blanks are treated as zeros. Otherwise, the default is restored.
apnd (Append)
By default, all files opened for sequential access are positioned at their beginning. It is sometimes necessary or convenient to open at the end-of-file, so that a write will append to the existing data. If apnd is
.TRUE.
, then files opened subsequently on any logical unit are positioned at their end upon opening. A value of
.FALSE.
restores the default behavior.
prefix (Automatic File Connection)
If the argument prefix is a nonblank string, then names of the form prefixNN are sought in the program environment. The value associated with each such name found is used to open the logical unit NN for formatted sequential access.
This search and connection is provided only for NN between 0 and19, inclusive. For NN
>
19, nothing is done; see “Source Code” on page 375.
vrbose (
IOINIT
Activity)
If the argument vrbose is
.TRUE.
, then ioinit
reports on its own activity.
Example: The program myprogram
has the following ioinit
call: call ioinit( .true., .false., .false., 'FORT', .false.)
You can assign file name in at least two ways.
FORTRAN 77 Reference Manual
7
In sh
: demo$ FORT01=mydata demo$ FORT12=myresults demo$ export FORT02 FORT12 demo$ myprogram
In csh
: demo% setenv FORT01 mydata demo% setenv FORT12 myresults demo% myprogram
With either shell, the ioinit
call in the above example gives these results:
•
Open logical unit 1 to the file, mydata
.
•
Open logical unit 12 to the file, myresults
.
•
Both files are positioned at their beginning.
•
Any formatted output has column 1 removed and interpreted as carriage control.
•
Embedded and trailing blanks are to be ignored on input.
Example: ioinit()
—list and compile: demo% cat tioinit.f character*3 s call ioinit( .true., .false., .false., 'FORT', .false.) do i = 1, 2 read( 1, '(a3,i4)') s, n write( 12, 10 ) s, n end do
10 format(a3,i4) end demo% cat tioinit.data abc 123
PDQ 789 demo% f77 -silent tioinit.f demo%
FORTRAN 77 Library Routines
377
7
You can set environment variables as follows, using either sh
or csh
: ioinit()
— sh
: demo$ FORT01=tioinit.data demo$ FORT12=tioinit.au demo$ export tioinit.data tioinit.au demo$ ioinit()
— csh
: demo% a.out demo% cat tioinit.au abc 123
PDQ 789 demo% ioinit()
—Run and test: demo% a.out demo% cat tioinit.au abc 123
PDQ 789 demo%
7.32
kill
: Send a Signal to a Process
The function is:
status
= kill(
pid
,
signum
)
pid
INTEGER
Input
signum
Return value
INTEGER
INTEGER
Input
Output
Process ID of one of the user’s processes
Valid signal number. See signal
(3).
status=0: OK
status>0: Error code
378
FORTRAN 77 Reference Manual
7
Example (fragment): Send a message using kill()
: integer kill, pid, signum
* … status = kill( pid, signum ) if ( status .ne. 0 ) stop 'kill: error' write(*,*) 'Sent signal ', signum, ' to process ', pid end
This function just sends a message; it does not necessarily kill the process.
Some users have been known to consider this a UNIX misnomer. If you really want to kill a process, see the following example.
Example (fragment): Kill a process using kill()
:
status
= kill(
pid
, SIGKILL )
See also: kill
(2), signal
(3), signal
(3F), fork
(3F), and perror
(3F).
7.33
libm_double
:
libm
Double-Precision Functions
These subprograms are double-precision libm
functions and subroutines.
Intrinsic Functions
The following FORTRAN 77 intrinsic functions return double-precision values if they have double-precision arguments. You need not put them in a type statement. If the function needed is available as an intrinsic function, it is simpler to use an intrinsic than a non-intrinsic function.
The
♦
symbol indicates it is nonstandard that this is an intrinsic function.
sqrt(x) log(x) log10(x) exp(x) x**y sin(x) cos(x) tan(x) asin(x) acos(x) atan(x) atan2(x,y) sinh(x) cosh(x) tanh(x) sind(x)
♦ cosd(x) asind(x)
♦
♦ acosd(x) atand(x)
♦
♦ atan2d(x,y) aint(x) anint(x) nint(x)
♦
FORTRAN 77 Library Routines
379
7
Non-Intrinsic Functions
In general, these functions do not correspond to standard FORTRAN 77 generic intrinsic functions—data types are determined by the usual data typing rules.
Example: Subroutine and non-Intrinsic double-precision functions:
The
DOUBLE PRECISION functions used are in a
DOUBLE
PRECISION
statement.
DOUBLE PRECISION c, d_acosh, d_hypot, d_infinity, s, x, y, z
...
z = d_acosh( x ) i = id_finite( x ) z = d_hypot( x, y ) z = d_infinity()
CALL d_sincos( x, s, c )
For meanings of routines and arguments, type man
on the routine name without the d_
; it is a C man page, but the meanings are the same.
Table 7-1
DOUBLE PRECISION libm
Functions
Variables c
, l
, p
, s
, u
, x
, and y are of type
DOUBLE PRECISION
.
If you use one of these
PRECISION into a statement).
DOUBLE
functions, put it
DOUBLE PRECISION statement (or type it by some
IMPLICIT sind(x)
, asind(x)
, … involve
degrees rather than radians.
d_acos( x ) d_acosd( x ) d_acosh( x ) d_acosp(
x
) d_acospi( x ) d_atan( x ) d_atand( x ) d_atanh( x ) d_atanp( x ) d_atanpi( x ) d_asin( x ) d_asind( x ) d_asinh( x ) d_asinp( x ) d_asinpi( x ) d_atan2(( y, x ) d_atan2d( y, x ) d_atan2pi( y, x )
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function arc cosine arc cosh arc tangent arc tanh arc sine arc sinh arc tangent
380
FORTRAN 77 Reference Manual
7
Table 7-1
DOUBLE PRECISION libm
Functions (Continued) d_cbrt(
x
) d_ceil(
x
) d_copysign(
x
,
x
) d_cos( x ) d_cosd( x ) d_cosh( x ) d_cosp( x ) d_cospi( x ) d_erf( x ) d_erfc( x ) d_expm1( x ) d_floor( x ) d_hypot( x, y ) d_infinity( ) d_j0( x ) d_j1( x ) d_jn( x )
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION id_finite( x ) id_fp_class( x ) id_ilogb( x ) id_irint( x ) id_isinf( x ) id_isnan( x ) id_isnormal( x ) id_issubnormal( x ) id_iszero( x ) id_signbit( x ) d_addran() d_addrans(x, p, l, u) d_lcran() d_lcrans(x, p, l, u ) d_shufrans(x, p, l,u) d_lgamma( x ) d_logb( x ) d_log1p( x ) d_log2( x )
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
DOUBLE PRECISION n/a
DOUBLE PRECISION n/a n/a
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Subroutine
Subroutine
Subroutine
Function
Function
Function
Function cube root ceiling cosine hyperbolic cos error function
(e**x)-1 floor hypotenuse bessel random number generators log gamma
FORTRAN 77 Library Routines
381
7
Table 7-1
DOUBLE PRECISION libm
Functions (Continued) d_max_normal() d_max_subnormal() d_min_normal() d_min_subnormal() d_nextafter( x, y ) d_quiet_nan( n ) d_remainder( x, y ) d_rint( x ) d_scalb( x, y ) d_scalbn( x, n ) d_signaling_nan( n ) d_significand( x ) d_sin( x ) d_sind( x ) d_sinh( x ) d_sinp( x ) d_sinpi( x ) d_sincos( x, s, c ) d_sincosd( x, s, c ) d_sincosp( x, s, c ) d_sincospi( x, s, c ) d_tan( x ) d_tand( x ) d_tanh( x ) d_tanp( x ) d_tanpi( x ) d_y0( x ) d_y1( x ) d_yn( n,x )
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION n/a n/a n/a n/a
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
DOUBLE PRECISION
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Subroutine
Subroutine
Subroutine
Subroutine
Function
Function
Function
Function
Function
Function
Function
Function
See also: intro
(3M) and the Numerical Computation Guide.
sine hyperbolic sin sine and cosine tangent hyperbolic tan bessel
382
FORTRAN 77 Reference Manual
7
7.34
libm_quadruple
:
libm
Quad-Precision Functions
These subprograms are quadruple-precision (
REAL*16
) libm
functions and subroutines (SPARC only).
Intrinsic Functions
The following FORTRAN 77 intrinsic functions return quadruple-precision values if they have quadruple-precision arguments. You need not put them in a type statement. If the function needed is available as an intrinsic function, it is simpler to use an intrinsic than a non-intrinsic function.
The
♦
symbol indicates it is nonstandard that this is an intrinsic function.
sqrt(x) log(x) log10(x) exp(x) x**y sin(x) cos(x) tan(x) asin(x) acos(x) atan(x) atan2(x,y) sinh(x) cosh(x) tanh(x) sind(x)
♦ cosd(x) asind(x) acosd(x) atand(x)
♦
♦
♦
♦ atan2d(x,y) aint(x) anint(x) nint(x)
♦
Non-Intrinsic Functions
In general, these do not correspond to standard generic intrinsic functions; data types are determined by the usual data typing rules.
Samples: Quadruple precision functions:
The quadruple precision functions used are in a
REAL*16 statement.
REAL*16 c, q_acosh, q_hypot, q_infinity, s, x, y, z
...
z = q_acosh( x ) i = iq_finite( x ) z = q_hypot( x, y ) z = q_infinity()
CALL q_sincos( x, s, c )
FORTRAN 77 Library Routines
383
7
Table 7-2
Quadruple-Precision libm
Functions
The variables y c
, l
, p
, s
, u
, x
, and
are of type quadruple precision.
If you use one of these quadruple precision functions, put it into a
REAL*16 some
statement (or type it by
IMPLICIT
statement).
sind(x)
, asind(x)
, … involve
degrees
rather than
radians
.
For meanings of routines and arguments, type man
on the routine name without the q_; it is a
C man page for the double precision function, but the meanings are the same.
q_copysign( x, y ) q_fabs( x ) q_fmod( x ) q_infinity( ) iq_finite( x ) iq_fp_class( x ) iq_ilogb( x ) iq_isinf( x ) iq_isnan( x ) iq_isnormal( x ) iq_issubnormal( x ) iq_iszero( x ) iq_signbit( x ) q_max_normal() q_max_subnormal() q_min_normal() q_min_subnormal() q_nextafter( x, y ) q_quiet_nan( n ) q_remainder( x, y ) q_scalbn( x, n ) q_signaling_nan( n )
REAL*16
REAL*16
REAL*16
REAL*16
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
REAL*16
REAL*16
REAL*16
REAL*16
REAL*16
REAL*16
REAL*16
REAL*16
REAL*16
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
If you need to use any other quadruple-precision libm
function, you can call it using
$PRAGMA C(
fcn
)
before the call. For details, read the chapter, “The C–
FORTRAN 77 Interface” in the FORTRAN 77 User’s Guide.
384
FORTRAN 77 Reference Manual
7
7.35
libm_single
:
libm
Single-Precision Functions
These subprograms are single-precision libm
functions and subroutines.
Intrinsic Functions
The following FORTRAN 77 intrinsic functions return single-precision values if they have single-precision arguments. If the function needed is available as an
intrinsic function, it may be simpler to use it than a non-intrinsic function.
The
♦
symbol indicates it is nonstandard that this is an intrinsic function.
sqrt(x) log(x) log10(x) exp(x) x**y sin(x) cos(x) tan(x) asin(x) acos(x) atan(x) atan2(x,y) sinh(x) cosh(x) tanh(x) sind(x)
♦ cosd(x) asind(x) acosd(x) atand(x)
♦
♦
♦
♦ atan2d(x,y) aint(x) anint(x) nint(x)
♦
Non-Intrinsic Functions
In general, the functions below provide access to single-precision libm functions that do not correspond to standard FORTRAN 77 generic intrinsic functions—data types are determined by the usual data typing rules.
Samples: Single-precision libm
functions:
The
REAL
functions used are not in a
REAL
statement. The type is determined by the default typing rules for the letter r
.
REAL c, s, x, y, z
..
z = r_acosh( x ) i = ir_finite( x ) z = r_hypot( x, y ) z = r_infinity()
CALL r_sincos( x, s, c )
FORTRAN 77 Library Routines
385
7
Variables c
, l
, p
, s
, u
, x
, and y are of type
REAL
.
If you use one of these
REAL functions, it will get the default type of
REAL
, unless you have some
IMPLICIT
statement for variables starting with r
.
sind(x)
, asind(x)
, … involve
degrees rather than radians.
For meanings of routines and arguments, type man
on the routine name without the r_
; it is a C man page, but the meanings are the same.
Table 7-3
Single-Precision libm
Functions r_acos( x ) r_acosd( x ) r_acosh( x ) r_acosp( x ) r_acospi( x ) r_atan( x ) r_atand( x ) r_atanh( x ) r_atanp( x ) r_atanpi( x ) r_asin( x ) r_asind( x ) r_asinh( x ) r_asinp( x ) r_asinpi( x ) r_atan2(( y, x ) r_atan2d( y, x ) r_atan2pi( y, x ) r_cbrt( x ) r_ceil( x ) r_copysign( x, y ) r_cos( x ) r_cosd( x ) r_cosh( x ) r_cosp( x ) r_cospi( x ) r_erf( x ) r_erfc( x ) r_expm1( x ) r_floor( x ) r_hypot( x, y ) r_infinity( ) r_j0( x ) r_j1( x ) r_jn( x )
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function arc cosine arc cosh arc tangent arc tanh arc sine arc sinh arc tangent cube root ceiling cosine hyperbolic cos error function
(e**x)-1 floor hypotenuse bessel
386
FORTRAN 77 Reference Manual
7
Table 7-3
Single-Precision libm
Functions (Continued) ir_finite( x ) ir_fp_class( x ) ir_ilogb( x ) ir_irint( x ) ir_isinf( x ) ir_isnan( x ) ir_isnormal( x ) ir_issubnormal( x ) ir_iszero( x ) ir_signbit( x ) r_addran() r_addrans( x, p, l, u ) r_lcran() r_lcrans( x, p, l, u ) r_shufrans(x, p, l, u) r_lgamma( x ) r_logb( x ) r_log1p( x ) r_log2( x )
REal n/a
REAL n/a n/a
REAL
REAL
REAL
REAL r_max_normal() r_max_subnormal() r_min_normal() r_min_subnormal() r_nextafter( x, y ) r_quiet_nan( n ) r_remainder( x, y ) r_rint( x ) r_scalb( x, y ) r_scalbn( x, n ) r_signaling_nan( n ) r_significand( x ) r_sin( x ) r_sind( x ) r_sinh( x ) r_sinp( x ) r_sinpi( x )
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Function
Subroutine
Subroutine
Subroutine
Function
Function
Function
Function random number log gamma sine hyperbolic sin
FORTRAN 77 Library Routines
387
7
Table 7-3
Single-Precision libm
Functions (Continued) r_sincos( x, s, c ) r_sincosd( x, s, c ) r_sincosp( x, s, c ) r_sincospi( x, s, c ) r_tan( x ) r_tand( x ) r_tanh( x ) r_tanp( x ) r_tanpi( x ) r_y0( x ) r_y1( x ) r_yn( n, x ) n/a n/a n/a n/a
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
Subroutine
Subroutine
Subroutine
Subroutine
Function
Function
Function
Function
Function
Function
Function
Function
See also: intro
(3M) and the Numerical Computation Guide.
sine & cosine tangent hyperbolic tan bessel
7.36
link
,
symlnk
: Make a Link to an Existing File
link
creates a link to an existing file.
symlink
creates a symbolic link to an existing file.
The functions are: status = link(
name1
,
name2
) status = symlnk(
name1
,
name2
)
name1 name2
Return value character* character*
INTEGER
n n
Input
Input
Path name of an existing file
Path name to be linked to the file, name1.
name2 must not already exist.
Output status=0: OK
status>0: System error code
388
FORTRAN 77 Reference Manual
7
link
: Create a Link to an Existing File
Example 1: link
: Create a link named data1
to the file, tlink.db.data.1
: character*34 name1/'tlink.db.data.1'/, name2/'data1'/ integer link, status status = link( name1, name2 ) if ( status .ne. 0 ) stop 'link: error' end demo% f77 -silent tlink.f demo% ls -l data1 data1 not found demo% a.out demo% ls -l data1
-rw-rw-r-- 2 generic 2 Aug 11 08:50 data1 demo%
symlnk
: Create a Symbolic Link to an Existing File
Example 2: symlnk
: Create a symbolic link named data1
to the file, tlink.db.data.1
: character*34 name1/'tlink.db.data.1'/, name2/'data1'/ integer status, symlnk status = symlnk( name1, name2 ) if ( status .ne. 0 ) stop 'symlnk: error' end demo% f77 -silent tsymlnk.f demo% ls -l data1 data1 not found demo% a.out demo% ls -l data1 lrwxrwxrwx 1 generic 15 Aug 11 11:09 data1 -> tlink.db.data.1
demo%
See also: link
(2), symlink
(2), perror
(3F), and unlink
(3F).
Note this bug: the path names cannot be longer than
MAXPATHLEN
as defined in
<sys/param.h>
.
FORTRAN 77 Library Routines
389
7
7.37
loc
: Return the Address of an Object
The function is:
k
= loc(
arg
)
arg
Any type
Return value
INTEGER
Example: loc
:
Input
Output
Name of any variable, array, or structure
Address of arg integer k, loc real arg / 9.0 / k = loc( arg ) write(*,*) k end
7.38
long
,
short
: Integer Object Conversion
long
and short
handle integer object conversions.
long
: Convert a Short Integer to a Long Integer
The function is: call
ExpecLong
( long(
int2
) )
int2
INTEGER*2
Return value
INTEGER*4
Input
Output
short
: Convert a Long Integer to a Short Integer
The function is: call
ExpecShort
( short(
int4
) )
int4
Return value
INTEGER*4
INTEGER*2
Input
Output
390
FORTRAN 77 Reference Manual
7
Example (fragment): long()
and short()
: integer*4 int4/8/, long integer*2 int2/8/, short call ExpecLong( long(int2) ) call ExpecShort( short(int4) )
… end long
is useful if constants are used in calls to library routines and the code is compiled with the
-i2
option.
short
is useful in similar context when an otherwise long object must be passed as a short integer.
7.39
longjmp
,
isetjmp
: Return to Location Set by
isetjmp
isetjmp
sets a location for longjmp
; longjmp
returns to that location.
isetjmp
: Set the Location for
longjmp
The function is:
ival
= isetjmp(
env
)
env
integer env(12)
Output
Return value
INTEGER
Output
env is a 12-word integer array
ival = 0 if isetjmp
is called explicitly
ival
≠
0 if isetjmp
is called through longjmp
FORTRAN 77 Library Routines
391
7
longjmp
: Return to the location set by
isetjmp
The subroutine is:
call
longjmp(
env
,
ival
)
env
integer env(12)
Input
ival
INTEGER
Output
env is the 12-word integer array initialized by isetjmp
ival = 0 if isetjmp
is called explicitly
ival
≠
0 if isetjmp
is called through longjmp
Description
The isetjmp
and longjmp
routines are used to deal with errors and interrupts encountered in a low-level routine of a program.
These routines should be used only as a last resort. They require discipline, and are not portable. Read the man page, setjmp
(3V), for bugs and other details.
isetjmp
saves the stack environment in env. It also saves the register environment.
longjmp
restores the environment saved by the last call to isetjmp
, and returns in such a way that execution continues as if the call to isetjmp
had just returned the value ival.
The integer expression ival returned from isetjmp
is zero if longjmp
is not called, and nonzero if longjmp
is called.
392
FORTRAN 77 Reference Manual
7
Example: Code fragment using isetjmp
and longjmp
: integer env(12) common /jmpblk/ env j = isetjmp( env ) !
← isetjmp if ( j .eq. 0 ) then call sbrtnA else call error_processor end if end subroutine sbrtnA integer env(12) common /jmpblk/ env call longjmp( env, ival ) !
← longjmp return end
Restrictions
You must invoke isetjmp
before calling longjmp()
.
The argument to isetjmp
must be a 12-integer array.
You must pass the env variable from the routine that calls isetjmp
to the routine that calls longjmp
, either by common or as an argument.
longjmp
attempts to clean up the stack.
longjmp
must be called from a lower call-level than isetjmp
.
Passing isetjmp
as an argument that is a procedure name does not work.
See setjmp
(3V).
FORTRAN 77 Library Routines
393
7
7.40
malloc
: Allocate Memory and Get Address
The function is:
k
= malloc(
n
)
n
Return value
INTEGER
Input Number of bytes of memory
INTEGER
Output k>0: k=address of the start of the block of memory allocated
k=0: Error
The function malloc
allocates an area of memory and returns the address of the start of that area. The region of memory is not initialized in any way— assume it is garbage.
Example: Code fragment using malloc()
: pointer ( p1, X )
… p1 = malloc( 1000 ) if ( p1 .eq. 0 ) stop 'malloc: cannot allocate'
… end
In the above example, we get 1,000 bytes of memory.
See also Section 7.15, “free: Deallocate Memory Allocated by Malloc,” for more details.
394
FORTRAN 77 Reference Manual
7
7.41
mvbits
: Move a Bit Field
call mvbits(
src
,
ini1
,
nbits
,
des
,
ini2
)
src
INTEGER
Input Source
ini1 nbits
INTEGER
INTEGER
Input
Input
Initial bit position in the source
Number of bits to move
des ini2
INTEGER
INTEGER
Output
Input
Destination
Initial bit position in the destination
Example: mvbits
: demo% cat mvb1.f
* mvb1.f -- From src, initial bit 0, move 3 bits to des, initial bit 3.
* src des
* 543210 543210
←
Bit numbers (VMS convention)
* 000111 000001
←
Values before move
* 000111 111001
←
Values after move
integer src, ini1, nbits, des, ini2
& data src, ini1, nbits, des, ini2
/ 7, 0, 3, 1, 3 / call mvbits ( src, ini1, nbits, des, ini2 ) write (*,"(5o3)") src, ini1, nbits, des, ini2 end demo% f77 -silent mvb1.f demo% a.out
7 0 3 71 3 demo%
If you use idate
or time
, you get VMS versions.
Note the following:
•
Bits are numbered according to VMS convention: from low-ordered end (as in the example above).
•
mvbits
changes only bits ini2 through ini2
+
nbits
-1
of the des location, and no bits of the src location.
FORTRAN 77 Library Routines
395
7
•
The restrictions are:
•
ini1 + nbits
≤
32
•
ini2 + nbits
≤
32
7.42
perror
,
gerror
,
ierrno
: Get System Error Messages
These routines perform the following functions: perror gerror ierrno
Print a message to FORTRAN 77 logical unit 0, stderr
.
Get a system error message (of the last detected system error)
Get the error number of the last detected system error.
perror
: Print Message to Logical Unit 0,
stderr
The subroutine is: call perror(
string
)
string
character
*n Input The message. It is written preceding the standard error message for the last detected system error.
Example 1:
…
… call perror( "file is for formatted I/O" )
gerror
: Get Message for Last Detected System Error
The subroutine or function is: call gerror(
string
)
string
character
*n Output Message for the last detected system error
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7
Example 2: gerror()
as a subroutine: character string*30
… call gerror ( string ) write(*,*) string end
Example 3: gerror
() as a function; string not used: character gerror*30, z*30
… z = gerror( ) write(*,*) z end
ierrno
: Get Number for Last Detected System Error
The function is:
n
= ierrno()
Return value
INTEGER
Output Error number of last detected system error
This number is updated only when an error actually occurs. Most routines and
I/O statements that might generate such errors return an error code after the call; that value is a more reliable indicator of what caused the error condition.
Example 4: ierrno()
: integer ierrno, n
… n = ierrno() write(*,*) n end
See also intro
(2) and perror
(3).
FORTRAN 77 Library Routines
397
398
7
Note these bugs:
•
string in the call to perror
cannot be longer than 127 characters.
•
The length of the string returned by gerror
is determined by the calling program.
f77
I/O Error Codes and Meanings
If the error number is less than 1000, then it is a system error. See intro
(2).
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1008
1009
1010
1011
1012
1013
1014
1015
1000
1001
1002
1003
1004
1005
1006
1007 error in format illegal unit number formatted io not allowed unformatted io not allowed direct io not allowed sequential io not allowed can't backspace file off beginning of record can't stat file no * after repeat count off end of record
<not used> incomprehensible list input out of free space unit not connected read unexpected character illegal logical input field
'new' file exists can't find 'old' file unknown system error requires seek ability illegal argument negative repeat count illegal operation for unit
<not used> incompatible specifiers in open illegal input for namelist error in FILEOPT parameter
FORTRAN 77 Reference Manual
7
7.43
putc
,
fputc
: Write a Character to a Logical Unit
putc
writes to logical unit 6, normally the control terminal output.
fputc
writes to a logical unit.
These functions write a character to the file associated with a FORTRAN 77 logical unit bypassing normal FORTRAN 77 I/O.
For any one unit, do not mix normal FORTRAN 77 output with output by these functions.
putc
: Write to Logical Unit 6
The function is:
status
= putc(
char
)
char
Return value character
INTEGER
Input The character to write to the unit
Output status=0: OK
status>0: System error code
Example: putc()
: character char, s*10 / 'OK by putc' / integer putc, status do i = 1, 10 char = s(i:i) status = putc( char ) end do status = putc( '\n' ) end demo% f77 -silent tputc.f demo% a.out
OK by putc demo%
FORTRAN 77 Library Routines
399
7
fputc
: Write to Specified Logical Unit
The function is:
status
= fputc(
lunit
,
char
)
lunit char
Return value
INTEGER character
Input
INTEGER
Input
Output
The unit to write to
The character to write to the unit
status=0: OK
status>0: System error code
Example: fputc()
: character char, s*11 / 'OK by fputc' / integer fputc, status open( 1, file='tfputc.data') do i = 1, 11 char = s(i:i) status = fputc( 1, char ) end do status = fputc( 1, '\n' ) end demo% f77 -silent tfputc.f demo% a.out demo% cat tfputc.data
OK by fputc demo%
See also putc
(3S), intro
(2), and perror
(3F).
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FORTRAN 77 Reference Manual
7
7.44
qsort
: Sort the Elements of a One-dimensional Array
The subroutine is: call qsort(
array
,
len
,
isize
,
compar
)
array
array
Input Contains the elements to be sorted
len isize compar
INTEGER
INTEGER function name
Input
Input
Input
Number of elements in the array.
Size of an element, typically:
4 for integer or real
8 for double precision or complex
16 for double complex
Length of character object for character arrays
Name of a user-supplied
INTEGER*2
function
The function compar(
arg1
,
arg2
) determines the sorting order. The two arguments are elements of array. The function must return:
Negative
Zero
Positive
Example: qsort()
:
If arg1 is considered to precede arg2
If arg1 is equivalent to arg2
If arg1 is considered to follow arg2 external compar integer*2 compar integer array(10)/5,1,9,0,8,7,3,4,6,2/, len/10/, isize/4/ call qsort( array, len, isize, compar ) write(*,'(10i3)') array end integer*2 function compar( a, b ) integer a, b if ( a .lt. b ) compar = -1 if ( a .eq. b ) compar = 0 if ( a .gt. b ) compar = 1 return end
FORTRAN 77 Library Routines
401
7
Compile and run the above source: demo% f77 -silent tqsort.f demo% a.out
0 1 2 3 4 5 6 7 8 9 demo%
See also qsort
(3).
7.45
ran
: Generate a Random Number between 0 and 1
Repeated calls to ran
generate a sequence of random numbers with a uniform distribution.
r
= ran(
i
)
i r
INTEGER*4
REAL
See lcrans
(3m).
Example: ran
:
Input Variable or array element
Output Variable or array element demo% cat ran1.f
* ran1.f -- Generate random numbers.
integer i, n real r(10) i = 760013 do n = 1, 10 r(n) = ran ( i ) end do write ( *, "( 5 f11.6 )" ) r end demo% f77 -silent ran1.f demo% a.out
0.222058 0.299851 0.390777 0.607055 0.653188
0.060174 0.149466 0.444353 0.002982 0.976519
demo%
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Note the following:
•
The range includes 0.0 and excludes 1.0.
•
The algorithm is a multiplicative, congruential type, general random number generator.
•
In general, the value of i
is set once during execution of the calling program.
•
The initial value of i
should be a large odd integer.
•
Each call to
RAN
gets the next random number in the sequence.
•
To get a different sequence of random numbers each time you run the program, you must set the argument to a different initial value for each run.
•
The argument is used by
RAN
to store a value for the calculation of the next random number according to the following algorithm:
SEED = 6909 * SEED + 1 (MOD 2**32)
•
SEED
contains a 32-bit number, and the high-order 24 bits are converted to floating point, and that value is returned.
7.46
rand
,
drand
,
irand
: Return Random Values
rand
returns real values in the range 0.0 through 1.0.
drand
returns double precision values in the range 0.0 through 1.0.
irand
returns positive integers in the range 0 through 2147483647.
FORTRAN 77 Library Routines
403
7
These functions use random
(3) to generate sequences of random numbers. The three functions share the same 256 byte state array. The only advantage of these functions is that they are widely available on UNIX systems. For better random number generators, compare lcrans
, addrans
, and shufrans
; also read the Numerical Computation Guide.
i
= irand(
k
)
r
= rand(
k
)
d
= drand(
k
)
k, r, d
INTEGER*4 rand drand irand
REAL*4
REAL*8
INTEGER*4
Input k=0: Get next random number in the sequence
k=1: Restart sequence, return first number
k>0: Use as a seed for new sequence, return first number
Output
Output
Output
Example: irand()
: integer*4 v(5), iflag/0/ do i = 1, 5 v(i) = irand( iflag ) end do write(*,*) v end demo% f77 -silent trand.f demo% a.out
2078917053 143302914 1027100827 1953210302 755253631 demo%
See also random
(3).
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FORTRAN 77 Reference Manual
7
7.47
rename
: Rename a File
The function is:
status = rename( from, to )
from
character*
n to
Return value character*
n
INTEGER
Input Path name of an existing file
Input New path name for the file
Output status=0: OK
status>0: System error code
If to exists, then both from and to must be the same type of file, and must reside on the same file system. If to exists, it is removed first.
Example: rename()
—Rename file trename.old
to trename.new
: integer rename, status character*18 from/'trename.old'/, to/'trename.new'/ status = rename( from, to ) if ( status .ne. 0 ) stop 'rename: error' end demo% f77 - silent trename.f demo% ls trename* trename.f trename.old
demo% a.out demo% ls trename* trename.f trename.new
demo%
See also rename
(2) and perror
(3F).
Note the bug: the path names cannot be longer than
MAXPATHLEN
as defined in
<sys/param.h>
.
FORTRAN 77 Library Routines
405
7
7.48
secnds
: Get System Time in Seconds, Minus Argument
t
= secnds(
t0
)
t0
REAL
Input
Return
Value
REAL
Output
Example: secnds
:
Constant, variable, or array element
Number of seconds since midnight, minus t0 demo% cat sec1.f real elapsed, t0, t1, x, y t0 = 0.0
t1 = secnds( t0 ) y = 0.1
do i = 1, 1000 x = asin( y ) end do elapsed = secnds( t1 ) write ( *, 1 ) elapsed
1 format ( ' 1000 arcsines: ', f12.6, ' sec' ) end demo% f77 -silent sec1.f demo% a.out
1000 arcsines: 6.699141 sec demo%
Note that:
•
The returned value from
SECNDS
is accurate to 0.01 second.
•
The value is the system time, as the number of seconds from midnight, and it correctly spans midnight.
•
Some precision may be lost for small time intervals near the end of the day.
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FORTRAN 77 Reference Manual
7
7.49
sh
: Fast Execution of an
sh
Command
The function is:
status
= sh(
string
)
string
character*
n
Return value
INTEGER
Input String containing command to do
Output Exit status of the shell executed.
See wait
(2) for an explanation of this value.
Example: sh()
: character*18 string / 'ls > MyOwnFile.names' / integer status, sh status = sh( string ) if ( status .ne. 0 ) stop 'sh: error'
...
end
The function sh
passes string to the sh
shell as input, as if the string had been typed as a command.
The current process waits until the command terminates.
The forked process
flushes all open files:
•
For output files, the buffer is flushed to the actual file.
•
For input files, the position of the pointer is unpredictable.
The sh()
function is not MT-safe. Do not call it from multithreaded programs; that is, do not call it from FORTRAN 77 MP programs.
See also: execve
(2), wait
(2), and system
(3).
Note this bug: string cannot be longer than 1,024 characters.
FORTRAN 77 Library Routines
407
7
7.50
signal
: Change the Action for a Signal
The function is:
n
= signal(
signum
,
proc
,
flag
)
signum
INTEGER
Input Signal number; see signal
(3)
proc flag
Return value
Routine name
INTEGER
INTEGER
Input
Input
Name of user signal handling routine; must be in an external statement
flag
<
0:
flag
≥
0:
Use proc as the signal handling routine
Ignore proc; pass flag as the action
flag
=0
: Use the default action
flag=1: Ignore this signal
Output
n
=
-1:
n
>
0:
n
>
1:
n
<
-1:
System error
Definition of previous action
n=Address of routine that would have been called
If signum is a valid signal number, then:
n=address of routine that would have been called.
If signum is a not a valid signal number, then:
n is an error number.
If proc is called, it is passed the signal number as an integer argument.
If a process incurs a signal, the default action is usually to clean up and abort.
You can change the action by writing an alternative signal handling routine, and then telling the system to use it.
You direct the system to use alternate action by calling signal
.
The returned value can be used in subsequent calls to signal
to restore a previous action definition.
You can get a negative return value even though there is no error. In fact, if you pass a valid signal number to signal()
, and you get a return value less than -
1, then it is OK.
f77
arranges to trap certain signals when a process is started. The only way to restore the default f77
action is to save the returned value from the first call to signal
.
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FORTRAN 77 Reference Manual
7
Example: Code fragment that uses signal()
—if illegal instruction signal, then call
MyAct
:
#include <signal.h> integer flag/-1/, n, signal external MyAct
… n = signal( SIGILL, MyAct, flag ) if ( n .eq. -1 ) stop 'Error from signal()' if ( n .lt. -1 ) write(*,*) 'From signal: n = ', -n
… end subroutine MyAct( signum ) integer signum
… return end
See also kill
(1), signal
(3), and kill
(3F).
7.51
sleep
: Suspend Execution for an Interval
The subroutine is: subroutine sleep(
itime
)
eyc
INTEGER
Input Number of seconds to sleep
The actual time can be up to 1 second less than itime due to granularity in system timekeeping.
Example: sleep()
: integer time / 5 / write(*,*) 'Start' call sleep( time ) write(*,*) 'End' end
See also sleep
(3).
FORTRAN 77 Library Routines
409
7
7.52
stat
,
lstat
,
fstat
: Get File Status
These functions return the following information: device, inode number, protection, number of hard links, user ID, group ID, device type, size, access time, modify time, status change time, optimal blocksize, blocks allocated
Both stat
and lstat
query by file name.
fstat
queries by logical unit.
stat
: Get Status for File, by File Name
The function is:
ierr
= stat (
name
,
statb
)
name
character*
n statb
INTEGER
Return value
INTEGER
Input Name of the file
Output Status structure for the file,
13-element array
Output ierr=0: OK
ierr>0: Error code
Example 1: stat()
: character name*18 /'MyFile'/ integer ierr, stat, lunit/1/, statb(13) open( unit=lunit, file=name ) ierr = stat ( name, statb ) if ( ierr .ne. 0 ) stop 'stat: error' write(*,*)'UID of owner = ',statb(5),', blocks = ',statb(13) end
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FORTRAN 77 Reference Manual
7
fstat
: Get Status for File, by Logical Unit
The function is:
ierr
= fstat (
lunit
,
statb
)
lunit statb
INTEGER
INTEGER
Input
Output
Return value
INTEGER
Output
Logical unit number
Status structure for the file, 13-element array
ierr=0: OK
ierr>0: Error code
Example 2: fstat()
: character name*18 /'MyFile'/ integer fstat, lunit/1/, statb(13) open( unit=lunit, file=name ) ierr = fstat ( lunit, statb ) if ( ierr .ne. 0 ) stop 'fstat: error' write(*,*)'UID of owner = ',statb(5),', blocks = ',statb(13) end
lstat
: Get Status for File, by File Name
The function is:
ierr
= lstat (
name
,
statb
)
name
character*
n statb
Return value
INTEGER
INTEGER
Input File name
Output Status array of file, 13 elements
Output ierr=0: OK
ierr>0: Error code
FORTRAN 77 Library Routines
411
412
7
Example 3: lstat()
: character name*18 /'MyFile'/ integer lstat, lunit/1/, statb(13) open( unit=lunit, file=name ) ierr = lstat ( name, statb ) if ( ierr .ne. 0 ) stop 'lstat: error' write(*,*)'UID of owner = ',statb(5),', blocks = ',statb(13) end
Detail of Status Array for Files
The meaning of the information returned in array statb is as described for the structure stat under stat
(2).
Spare values are not included. The order is shown in the following table: statb
(1) statb
(2) statb
(3) statb
(4) statb
(5) statb
(6) statb
(7) statb
(8) statb
(9) statb
(10) statb
(11) statb
(12) statb
(13)
Device inode resides on
This inode’s number
Protection
Number of hard links to the file
User ID of owner
Group ID of owner
Device type, for inode that is device
Total size of file
File last access time
File last modify time
File last status change time
Optimal blocksize for file system I/O ops
Actual number of blocks allocated
See also stat
(2), access
(3F), perror
(3F), and time
(3F).
Note this bug—the path names can be no longer than
MAXPATHLEN
as defined in
<sys/param.h>
.
FORTRAN 77 Reference Manual
7
7.53
system
: Execute a System Command
The function is:
status
= system(
string
)
string
character*
n
Return value
INTEGER
Input String containing command to do
Output Exit status of the shell executed.
See wait
(2) for an explanation of this value.
Example: system()
: character*8 string / 'ls s*' / integer status, system status = system( string ) if ( status .ne. 0 ) stop 'system: error' end
The function system
passes string to your shell as input, as if the string had been typed as a command.
If system
can find the environment variable
SHELL
, then system
uses the value of
SHELL
as the command interpreter (shell); otherwise, it uses sh
(1).
The current process waits until the command terminates.
Historically, cc
and f77
developed with different assumptions:
•
If cc
calls system
, the shell is always the Bourne shell.
•
If f77
calls system
, then which shell is called depends on the environment variable
SHELL
.
The system
function flushes all open files:
•
For output files, the buffer is flushed to the actual file.
•
For input files, the position of the pointer is unpredictable.
See also: execve
(2), wait
(2), and system
(3).
The system()
function is not MT-safe. Do not call it from multithreaded programs; that is, do not call it from FORTRAN 77 MP programs.
FORTRAN 77 Library Routines
413
7
Note the bug: string cannot be longer than 1,024 characters.
7.54
time
,
ctime
,
ltime
,
gmtime
: Get System Time
These routines have the following functions: time ctime ltime
Standard version: Get system time as integer (seconds since 0 GMT 1/1/70)
VMS Version: Get the system time as character (hh:mm:ss)
Convert a system time to an ASCII string.
Dissect a system time into month, day, and so forth, local time.
gmtime
Dissect a system time into month, day, and so forth, GMT.
time
: Get System Time
For time()
, there are two versions, a standard version and a VMS version. If you use the f77
command-line option
-lV77,
then you get the VMS version for time()
and for idate()
; otherwise, you get the standard versions.
Version Standard with Operating System
The function is:
n = time()
Return value
INTEGER
Output Time, in seconds, since 0:0:0, GMT, 1/1/70
The function time()
returns an integer with the time since 00:00:00 GMT,
January 1, 1970, measured in seconds. This is the value of the operating system clock.
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FORTRAN 77 Reference Manual
Do not use
-lV77
.
Use
-lV77
.
7
Example: time()
, version standard with the operating system: integer n, time n = time() write(*,*) 'Seconds since 0 1/1/70 GMT = ', n end demo% f77 -silent ttime.f demo% a.out
The time is: 771967850 demo%
VMS Version
This function time
gets the current system time as a character string.
The function is:
t
call time(
t
) character*8
Output Time, in the form hh:mm:ss
hh, mm, and ss are each two digits: hh is the hour; mm is the minute; ss is the second
Example: time(
t
)
, VMS version, ctime
—convert the system time to ASCII: character t*8 call time( t ) write(*, "(' The current time is ', A8 )") t end demo% f77 -silent ttimeV.f -lV77 demo% a.out
The current time is 08:14:13 demo%
FORTRAN 77 Library Routines
415
7
ctime
: Convert System Time to Character
The function
ctim
e converts a system time,
stime
, and returns it as a 24character ASCII string.
The function is:
string
= ctime(
stime
)
stime
INTEGER*4
Input System time from time()
(standard version)
Return value character*24
Output System time as character string. You must type ctime
and string as character*24
.
The format of the ctime
returned value is shown in the following example. It is described in the man
page ctime
, section 3C in Solaris 2.x, 3V in Solaris 1.x.
Example: ctime()
: character*24 ctime, string integer n, time n = time() string = ctime( n ) write(*,*) 'ctime: ', string end demo% f77 -silent tctime.f demo% a.out
ctime: Mon Aug 12 10:35:38 1991 demo%
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FORTRAN 77 Reference Manual
7
ltime
: Split System Time to Month, Day,… (Local)
This routine dissects a system time into month, day, and so forth, for the local time zone.
The subroutine is: call ltime(
stime
, tarray )
stime tarray
INTEGER*4
Input System time from time()
(standard version)
INTEGER*4(9)
Output System time, local, as day, month, year, …
For the meaning of the elements in tarray
, see the next section.
Example:
ltime
()
: integer*4 stime, tarray(9), time stime = time() call ltime( stime, tarray ) write(*,*) 'ltime: ', tarray end demo% f77 -silent tltime.f demo% a.out
ltime: 25 49 10 12 7 91 1 223 1 demo%
FORTRAN 77 Library Routines
417
7
gmtime
: Split System Time to Month, Day, … (GMT)
This routine dissects a system time into month, day, and so on, for GMT.
The subroutine is: call gmtime(
stime
,
tarray
)
stime
INTEGER*4
Input System time from time()
(standard version)
tarray
INTEGER*4(9)
Output System time, GMT, as day, month, year, …
Example: gmtime
: integer*4 stime, tarray(9), time stime = time() call gmtime( stime, tarray ) write(*,*) 'gmtime: ', tarray end demo% f77 -silent tgmtime.f demo% a.out
gmtime: 12 44 19 18 5 94 6 168 0 demo% tarray()
For Solaris1.x, the range for seconds is 0 - 59
Here are the tarray()
values, from ctime
: index, units, and range:
3
4
1
2
5
Seconds (0 - 61)
Minutes (0 - 59)
Hours (0 - 23)
Day of month (1 - 31)
Months since January (0 - 11)
8
9
6
7
Year - 1900
Day of week (Sunday = 0)
Day of year (0 - 365)
Daylight Saving Time,
1 if DST in effect
These values are described in the man
page ctime
, section 3C in Solaris 2.x, 3V in Solaris 1.x.
See also: ctime
, idate
(3F), and fdate
(3F).
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FORTRAN 77 Reference Manual
7
7.55
topen
,
tclose
,
tread
,…,
tstate
: Do Tape I/O
You can manipulate magnetic tape from FORTRAN 77 using these functions: topen tclose tread twrite trewin tskipf tstate
Associate a device name with a tape logical unit.
Write EOF, close tape device channel, and remove association with tlu.
Read next physical record from tape into buffer.
Write the next physical record from buffer to tape.
Rewind the tape to the beginning of the first data file.
Skip forward over files and/or records, and reset EOF status.
Determine the logical state of the tape I/O channel.
On any one unit, do not mix these functions with standard FORTRAN 77 I/O.
You must first use
topen
()
to open a tape logical unit, tlu, for the specified device. Then you do all other operations on the specified tlu. tlu has no relationship at all to any normal FORTRAN 77 logical unit.
Before you use one of these functions, its name must be in an
INTEGER
type statement.
topen
: Associate a Device with a Tape Logical Unit n
= topen(
tlu
,
devnam
,
islabeled
)
tlu islabeled
INTEGER
LOGICAL
Input
Input
Tape logical unit. It must be in the range 0 to 7.
True=the tape is labeled
A label is the first file on the tape.
Return value
INTEGER
Output n=0: OK
n<0: Error
This function does not move the tape. See perror
(3f) for details.
FORTRAN 77 Library Routines
419
7
420
EXAMPLE: topen()
—open a 1/4-inch tape file:
CHARACTER devnam*9 / '/dev/rst0' /
INTEGER n / 0 /, tlu / 1 /, topen
LOGICAL islabeled / .false. / n = topen( tlu, devnam, islabeled )
IF ( n .LT. 0 ) STOP "topen: cannot open"
WRITE(*,'("topen ok:", 2I3, 1X, A10)') n, tlu, devnam
END
The output is: topen ok: 0 1 /dev/rst0
tclose
: Write EOF, Close Tape Channel, Disconnect tlu n
= tclose (
tlu
)
tlu n
INTEGER
INTEGER
Input
Return value
Tape logical unit, in range 0 to 7
n=0: OK
n<0: Error
Caution –
tclose
()
places an EOF marker immediately after the current location of the unit pointer, and then closes the unit. So if you trewin()
a unit before you tclose()
it, its contents are discarded.
Example: tclose()
—close an opened 1/4-inch tape file:
CHARACTER devnam*9 / '/dev/rst0' /
INTEGER n / 0 /, tlu / 1 /, tclose, topen
LOGICAL islabeled / .false. / n = topen( tlu, devnam, islabeled ) n = tclose( tlu )
IF ( n .LT. 0 ) STOP "tclose: cannot close"
WRITE(*, '("tclose ok:", 2I3, 1X, A10)') n, tlu, devnam
END
FORTRAN 77 Reference Manual
7
The output is: tclose ok: 0 1 /dev/rst0
twrite
: Write Next Physical Record to Tape
n = twrite(
tlu
,
buffer
)
tlu buffer n
INTEGER
Input character
Input
INTEGER
Return value
Tape logical unit, in range 0 to 7
Must be sized at a multiple of 512
n
>
0: OK, and n = the number of bytes written
n=0: End of Tape
n<0: Error
The physical record length is the size of buffer
.
Example: twrite()
—write a 2-record file:
&
CHARACTER devnam*9 / '/dev/rst0' /, rec1*512 / "abcd" /, rec2*512 / "wxyz" /
INTEGER n / 0 /, tlu / 1 /, tclose, topen, twrite
LOGICAL islabeled / .false. / n = topen( tlu, devnam, islabeled )
IF ( n .LT. 0 ) STOP "topen: cannot open" n = twrite( tlu, rec1 )
IF ( n .LT. 0 ) STOP "twrite: cannot write 1" n = twrite( tlu, rec2 )
IF ( n .LT. 0 ) STOP "twrite: cannot write 2"
WRITE(*, '("twrite ok:", 2I4, 1X, A10)') n, tlu, devnam
END
The output is: twrite ok: 512 1 /dev/rst0
FORTRAN 77 Library Routines
421
7
tread
: Read Next Physical Record from Tape n
= tread(
tlu
,
buffer
)
tlu buffer n
INTEGER character
INTEGER
Input
Input
Tape logical unit, in range 0 to 7.
Must be sized at a multiple of 512, and must be large enough to hold the largest physical record to be read.
Return value n>0: OK, and n is the number of bytes read.
n<0: Error
n=0: EOF
If the tape is at EOF or EOT, then tread
does a return; it does not read tapes.
Example: tread()
—read the first record of the file written above:
CHARACTER devnam*9 / '/dev/rst0' /, onerec*512 / " " /
INTEGER n / 0 /, tlu / 1 /, topen, tread
LOGICAL islabeled / .false. / n = topen( tlu, devnam, islabeled )
IF ( n .LT. 0 ) STOP "topen: cannot open" n = tread( tlu, onerec )
IF ( n .LT. 0 ) STOP "tread: cannot read"
WRITE(*,'("tread ok:", 2I4, 1X, A10)') n, tlu, devnam
WRITE(*,'( A4)') onerec
END
The output is: tread ok: 512 1 /dev/rst0 abcd
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FORTRAN 77 Reference Manual
7
trewin
: Rewind Tape to Beginning of First Data File n
= trewin (
tlu
)
tlu n
INTEGER
Input Tape logical unit, in range 0 to 7
INTEGER
Return value n=0: OK
n<0: Error
If the tape is labeled, then the label is skipped over after rewinding.
Example 1: trewin()
—typical fragment:
CHARACTER devnam*9 / '/dev/rst0' /
INTEGER n /0/, tlu /1/, tclose, topen, tread, trewin
… n = trewin( tlu )
IF ( n .LT. 0 ) STOP "trewin: cannot rewind"
WRITE(*, '("trewin ok:", 2I4, 1X, A10)') n, tlu, devnam
…
END
Example 2: trewin()
—in a two-record file, try to read three records, rewind, read one record:
CHARACTER devnam*9 / '/dev/rst0' /, onerec*512 / " " /
INTEGER n / 0 /, r, tlu / 1 /, topen, tread, trewin
LOGICAL islabeled / .false. / n = topen( tlu, devnam, islabeled )
IF ( n .LT. 0 ) STOP "topen: cannot open"
DO r = 1, 3
n = tread( tlu, onerec )
WRITE(*,'(1X, I2, 1X, A4)') r, onerec
END DO n = trewin( tlu )
IF ( n .LT. 0 ) STOP "trewin: cannot rewind"
WRITE(*, '("trewin ok:" 2I4, 1X, A10)') n, tlu, devnam n = tread( tlu, onerec )
IF ( n .LT. 0 ) STOP "tread: cannot read after rewind"
WRITE(*,'(A4)') onerec
END
FORTRAN 77 Library Routines
423
424
7
The output is:
1 abcd
2 wxyz
3 wxyz trewin ok: 0 1 /dev/rst0 abcd
tskipf
: Skip Files and Records; Reset EoF Status n
= tskipf(
tlu
,
nf
,
nr
)
tlu nf nr
INTEGER
INTEGER
INTEGER
Input
Input
Input
n
INTEGER
Return value
Tape logical unit, in range 0 to 7
Number of end-of-file marks to skip over first
Number of physical records to skip over after skipping files
n=0: OK
n<0: Error
This function does not skip backward.
First, the function skips forward over nf end-of-file marks. Then, it skips forward over nr physical records. If the current file is at EOF, this counts as one file to skip. This function also resets the EOF status.
Example: tskipf()
—typical fragment: skip four files and then skip one record:
INTEGER nfiles / 4 /, nrecords / 1 /, tskipf, tlu / 1 /
… n = tskipf( tlu, nfiles, nrecords )
IF ( n .LT. 0 ) STOP "tskipf: cannot skip"
…
Compare with tstate
in the next section.
FORTRAN 77 Reference Manual
7
tstate
: Get Logical State of Tape I/O Channel n
= tstate(
tlu
,
fileno
,
recno
,
errf
,
eoff
,
eotf
,
tcsr
)
tlu fileno
INTEGER
INTEGER
Input
Output
Tape logical unit, in range 0 to 7
Current file number
recno errf eoff eotf tcsr
INTEGER
LOGICAL
LOGICAL
LOGICAL
Output
Output
Output
Output
Current record number
True=an error occurred
True=the current file is at EOF
True=tape has reached logical end-of-tape
INTEGER
Output True=hardware errors on the device. It contains the tape drive control status register. If the error is software, then tcsr is returned as zero. The values returned in this status register vary grossly with the brand and size of tape drive.
For details, see st
(4s).
While eoff is true, you cannot read from that tlu. You can set this EOF status flag to false by using tskipf()
to skip one file and zero records: n = tskipf( tlu, 1, 0).
Then you can read any valid record that follows.
End-of-tape (EOT) is indicated by an empty file, often referred to as a double
EOF
mark. You cannot read past EOT, but you can write past it.
FORTRAN 77 Library Routines
425
7
Example: Write three files of two records each:
CHARACTER devnam*10 / '/dev/nrst0' /,
& f0rec1*512 / "eins" /, f0rec2*512 / "zwei" /,
& f1rec1*512 / "ichi" /, f1rec2*512 / "ni__" /,
& f2rec1*512 / "un__" /, f2rec2*512 / "deux" /
INTEGER n / 0 /, tlu / 1 /, tclose, topen, trewin, twrite
LOGICAL islabeled / .false. / n = topen( tlu, devnam, islabeled ) n = trewin( tlu ) n = twrite( tlu, f0rec1 ) n = twrite( tlu, f0rec2 ) n = tclose( tlu ) n = topen( tlu, devnam, islabeled ) n = twrite( tlu, f1rec1 ) n = twrite( tlu, f1rec2 ) n = tclose( tlu ) n = topen( tlu, devnam, islabeled ) n = twrite( tlu, f2rec1 ) n = twrite( tlu, f2rec2 ) n = tclose( tlu )
END
The next example uses tstate()
to trap EOF and get at all files.
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FORTRAN 77 Reference Manual
7
Example: Use tstate()
in a loop that reads all records of the 3 files written in the previous example:
&
CHARACTER devnam*10 / '/dev/nrst0' /, onerec*512 / " " /
INTEGER f, n / 0 /, tlu / 1 /, tcsr, topen, tread, trewin, tskipf, tstate
LOGICAL errf, eoff, eotf, islabeled / .false. / n = topen( tlu, devnam, islabeled ) n = tstate( tlu, fn, rn, errf, eoff, eotf, tcsr )
WRITE(*,1) 'open:', fn, rn, errf, eoff, eotf, tcsr
1 FORMAT(1X, A10, 2I2, 1X, 1L, 1X, 1L,1X, 1L, 1X, I2 )
2 FORMAT(1X, A10,1X,A4,1X,2I2,1X,1L,1X,1L,1X,1L,1X,I2) n = trewin( tlu ) n = tstate( tlu, fn, rn, errf, eoff, eotf, tcsr )
WRITE(*,1) 'rewind:', fn, rn, errf, eoff, eotf, tcsr
DO f = 1, 3
eoff = .false.
DO WHILE ( .NOT. eoff )
&
n = tread( tlu, onerec )
n = tstate( tlu, fn, rn, errf, eoff, eotf, tcsr )
IF (.NOT. eoff) WRITE(*,2) 'read:', onerec, fn, rn, errf, eoff, eotf, tcsr
END DO
n = tskipf( tlu, 1, 0 )
n = tstate( tlu, fn, rn, errf, eoff, eotf, tcsr )
WRITE(*,1) 'tskip: ', fn, rn, errf, eoff, eotf, tcsr
END DO
END
The output is: open: 0 0 F F F 0 rewind: 0 0 F F F 0 read: eins 0 1 F F F 0 read: zwei 0 2 F F F 0 tskip: 1 0 F F F 0 read: ichi 1 1 F F F 0 read: ni__ 1 2 F F F 0 tskip: 2 0 F F F 0 read: un__ 2 1 F F F 0 read: deux 2 2 F F F 0 tskip: 3 0 F F F 0
FORTRAN 77 Library Routines
427
7
A summary of EOF and EOT follows:
•
If you are at either EOF or EOT, then:
•
Any tread()
just returns; it does not read the tape.
•
A successful tskipf(tlu,1,0)
resets the EOF status to false, and returns; it does not advance the tape pointer.
•
A successful twrite()
resets the EOF and EOT status flags to false.
•
A successful tclose()
resets all those flags to false.
•
tclose()
truncates; it places an EOF marker immediately after the current location of the unit pointer, and then closes the unit. So, if you use trewin()
to rewind a unit before you use tclose()
to close it, its contents are discarded. This behavior of tclose()
is inherited from the
Berkeley code.
See also: ioctl
(2), mtio
(4s), perror
(3f), read
(2), st
(4s), and write
(2).
7.56
ttynam
,
isatty
: Get Name of a Terminal Port
ttynam
and isatty
handle terminal port names.
name
= ttynam(
lunit
)
lunit
Return value
INTEGER character*
n n
ttynam
:
Get Name of a Terminal Port
The function ttynam
returns a blank padded path name of the terminal device associated with logical unit lunit.
The function is:
INTEGER
Input
Output
Logical unit
name is nonblank: name=path name of device on lunit.
name is an empty string (all blanks): lunit is not associated with a terminal device in the directory,
/dev
Size of name Must be large enough for the longest path name
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FORTRAN 77 Reference Manual
7
isatty
: Is this Unit a Terminal?
The function is:
terminal
= isatty(
lunit
)
lunit
Return value
INTEGER
Input Logical unit
LOGICAL
Output terminal=true: It is a terminal device
terminal=false: It is not a terminal device
Example: Determine if lunit is a tty: character*12 name, ttynam integer lunit /5/ logical isatty, terminal terminal = isatty( lunit ) name = ttynam( lunit ) write(*,*) 'terminal = ', terminal, ', name = "', name, '"' end
The output is:
terminal = T, name = "/dev/ttyp1 "
7.57
unlink
: Remove a File
The function is:
n
= unlink (
patnam
)
patnam
character*
n
Return value
INTEGER
Input File name
Output n=0: OK
n>0: Error
The function unlink
removes the file specified by path name patnam. If this is the last link to the file, the contents of the file are lost.
FORTRAN 77 Library Routines
429
7
Example: unlink()
—Remove the tunlink.data
file: call unlink( 'tunlink.data' ) end demo% f77 -silent tunlink.f demo% ls tunl* tunlink.f tunlink.data
demo% a.out demo% ls tunl* tunlink.f
demo%
See also: unlink
(2), link
(3F), and perror
(3F). Note this bug—the path names cannot be longer than
MAXPATHLEN
as defined in
<sys/param.h>
.
7.58
wait
: Wait for a Process to Terminate
The function is: n = wait(
status
)
status
INTEGER
Output Termination status of the child process
Return value
INTEGER
Output n>0: Process ID of the child process
n<0: n=System error code; see wait
(2).
wait
suspends the caller until a signal is received, or one of its child processes terminates. If any child has terminated since the last wait
, return is immediate. If there are no children, return is immediate with an error code.
Example: Code fragment using wait()
: integer n, status, wait
… n = wait( status ) if ( n .lt. 0 ) stop ’wait: error’
… end
See also: wait
(2), signal
(3F), kill
(3F), and perror
(3F).
430
FORTRAN 77 Reference Manual
VMS Language Extensions
This chapter describes the VMS language extensions that FORTRAN 77 supports. It is organized into the following sections:
Background
VMS Language Features You Get Automatically
VMS Language Features that Require -xl
Unsupported VMS FORTRAN
These extensions are all, of course, nonstandard. ♦
page 431 page 432 page 436 page 439
8
8.1 Background
This FORTRAN 77 compiler includes the VMS extensions to make it as easy as possible to port FORTRAN 77 programs from VMS environments to Solaris environments. The compiler provides almost complete compatibility with VMS
FORTRAN. These extensions are included in two systems:
•
Compiler command: f77
•
Debugger commands: debugger
, dbx
431
432
8
8.2 VMS Language Features You Get Automatically
This list is a summary of the VMS features that are included in f77
. Details are elsewhere in this manual.
•
Namelist I/O
•
Unlabeled
DO
…
END DO
•
Indefinite
DO WHILE
…
END DO
•
BYTE
data type
•
Logical operations on integers, and arithmetic operations on logicals
•
Additional field and edit descriptors for
FORMAT
statements:
•
Remaining characters (
Q
)
•
Carriage Control
($)
•
Octal (
O
)
•
Hexadecimal (
X
)
•
Hexadecimal (
Z
)
•
Default field indicators for w, d, and e fields in
FORMAT
statements
•
Reading into Hollerith edit descriptors
•
APPEND
option for
OPEN
•
Long names (32 characters)
•
_
and
$
in names
•
Long source lines (132-character), if the
-e
option is on
•
Records, structures, unions, and maps
•
Getting addresses by the
%LOC
function
•
Passing arguments by the
%VAL
function
•
End-of-line comments
•
OPTIONS
statement
•
VMS Tab-format source lines are valid.
FORTRAN 77 Reference Manual
8
•
Initialize in common
You can initialize variables in common blocks outside of
BLOCK DATA subprograms. You can initialize portions of common blocks, but you cannot initialize portions of one common block in more than one subprogram.
•
Radix-50
Radix-50 constants are implemented as f77
bit-string constants, that is, no type is assumed.
•
IMPLICIT NONE
is treated as
IMPLICIT UNDEFINED (A-Z)
•
VIRTUAL
is treated as
DIMENSION
.
•
Initialize in declarations
Initialization of variables in declaration statements is allowed. Example:
CHARACTER*10 NAME /'Nell'/
•
Noncharacter format specifiers
If a runtime format specifier is not of type
CHARACTER
, the compiler accepts that too, even though the FORTRAN 77 Standard requires the
CHARACTER type.
•
Omitted arguments in subprogram calls
The compiler accepts omitted actual argument in a subroutine call, that is, two consecutive commas compile to a null pointer. Reference to that dummy argument gives a segmentation fault.
•
REAL*16
(SPARC only) The compiler treats variables of type
REAL*16
as quadruple precision.
•
Noncharacter variables
The FORTRAN 77 Standard requires the
FILE=
specifier for
OPEN
and
INQUIRE
to be an expression of type
CHARACTER
.
f77
accepts a numeric variable or array element reference.
VMS Language Extensions
433
8
434
•
Consecutive operators f77
allows two consecutive arithmetic operators when the second operator is a unary
+
or
-
. Here are two consecutive operators:
X = A ** -B
The above statement is treated as follows:
X = A ** (-B)
•
Illegal real expressions
When the compiler finds a
REAL
expression where it expects an integer expression, it truncates and makes a type conversion to
INTEGER
.
Examples: Contexts for illegal real expressions that f77
converts to integer:
•
Alternate
RETURN
•
Dimension declarators and array subscripts
•
Substring selectors
•
Computed
GO TO
•
Logical unit number, record number, and record length
•
Typeless numeric constants
Binary, hexadecimal and octal constants are accepted in VMS form.
Example: Constants–Binary (
B
), Octal (
O
), Hexadecimal (
X
or
Z
):
DATA N1 /B'0011111'/, N2/O'37'/, N3/X'1f'/, N4/Z'1f'/
•
Function length on function name, rather than on the word
FUNCTION
The compiler accepts nonstandard length specifiers in function declarations.
Example: Size on function name, rather than on the word
FUNCTION
:
INTEGER FUNCTION FCN*2 ( A, B, C )
FORTRAN 77 Reference Manual
8
•
TYPE
and
ACCEPT
statements are allowed.
•
Alternate return
The nonstandard
&
syntax for alternate-return actual arguments is treated as the standard FORTRAN 77
*
syntax. Example:
CALL SUBX ( I, *100, Z ) !
Standard (OK)
CALL SUBX ( I, &100, Z ) !
Nonstandard (OK)
•
The
ENCODE
and
DECODE
statements are accepted.
•
Direct I/O with
'N
record specifier
The nonstandard record specifier
'N
for direct-access I/O statements is OK.
Example: A nonstandard form for record specifier:
READ ( K ' N ) LIST
The above is treated as:
READ ( UNIT=K, REC=N ) LIST
The logical unit number is
K
and the number of the record is
N
.
•
NAME
,
RECORDSIZE
, and
TYPE
options—
OPEN
has the following alternative options:
•
NAME
is treated as
FILE
•
RECORDSIZE
is treated as
RECL
•
TYPE
is treated as
STATUS
•
DISPOSE=
p
The
DISPOSE=
p clause in the
CLOSE
statement is treated as
STATUS=
p.
•
Special Intrinsics
The compiler processes certain special intrinsic functions:
•
%VAL
is OK as is
•
%LOC
is treated as
LOC
VMS Language Extensions
435
436
8
•
%REF(
expr
)
is treated as expr (with a warning if expr is
CHARACTER
)
•
%DESCR
is reported as an untranslatable feature
•
Variable Expressions in
FORMAT
Statements
In general, inside a
FORMAT
statement, any integer constant can be replaced by an arbitrary expression; the single exception is the n in an n
H
…
edit descriptor. The expression itself must be enclosed in angle brackets.
Example: The
6
in the following statement is a constant:
1 FORMAT( 3F6.1 )
6
can be replaced by the variable
N
, as in:
1 FORMAT( 3F<N>.1 )
8.3
VMS Language Features that Require
-xl
You get most VMS features automatically without any special options. For a few of them, however, you must add the
-xl
option on the f77
command line.
In general, you need this
-xl
option if a source statement can be interpreted for either a VMS way of behavior or an f77
way of behavior, and you want the
VMS way of behavior. The
-xl
option forces the compiler to interpret it as
VMS FORTRAN.
Summary of Features That Require
-xl[d]
You must use
-xl[d]
to access the following features:
•
Unformatted record size
in words rather than bytes (
-xl
)
•
VMS-style logical file names (
-xl
)
•
Quote (
"
) character introducing octal constants (
-xl
)
•
Backslash (
\
) as ordinary character within character constants (
-xl
)
•
Nonstandard form of the
PARAMETER
statement (
-xl
)
•
Debugging lines as comment lines or FORTRAN 77 statements (
-xld
)
•
Align structures as in VMS FORTRAN (
-xl
)
FORTRAN 77 Reference Manual
8
Details of Features That Require
-xl[d]
Here are the details:
•
Unformatted record size
in words rather than bytes
In f77
, direct-access, unformatted files are always opened with the logical record size in bytes.
If the
–xl[d]
option is not set, then the argument n in the
OPEN
option
RECL=
n is assumed to be the number of bytes to use for the record size.
If the
–xl[d]
option is set, then the argument n in the
OPEN
option
RECL=
n
is assumed to be the number of words, so the compiler uses n
*4
as the number of bytes for the record size.
If the
–xl[d]
option is set, and if the compiler cannot determine if the file is formatted or unformatted, then it issues a warning message that the record size may need to be adjusted. This result could happen if the information is passed in variable character strings.
The record size returned by an
INQUIRE
statement is not adjusted by the compiler; that is,
INQUIRE
always returns the number of bytes.
These record sizes apply to direct-access, unformatted files only.
•
VMS-style logical file names
If the
–xl[d]
option is set, then the compiler interprets VMS logical file names on the
INCLUDE
statement if it finds the environment variable,
LOGICALNAMEMAPPING
, to define the mapping between the logical names and the UNIX path name.
You set the environment variable to a string of the form:
"
lname1
=
path1
;
lname2
=
path2
; … "
Remember these rules for VMS style logical file names:
•
Each lname is a logical name and each path1, path2, and so forth, is the path name of a directory (without a trailing
/
).
•
It ignores all blanks when parsing this string.
•
It strips any trailing
/[no]list
from the file name in the
INCLUDE statement.
VMS Language Extensions
437
8
438
•
Logical names in a file name are delimited by the first
:
in the VMS file name.
•
It converts file names from lname1:file to the path1/file form.
•
For logical names, uppercase and lowercase are significant. If a logical name is encountered on the
INCLUDE
statement which is not specified in the
LOGICALNAMEMAPPING
, the file name is used, unchanged.
•
Quote (
"
) character introducing octal constants
If the
–xl[d]
compiler option is on, a VMS FORTRAN octal integer constant is treated as its decimal form.
Example: VMS octal integer constant:
JCOUNT = ICOUNT + "703
The above statement is treated as:
JCOUNT = ICOUNT + 451
If the
–xl[d]
option is not on, then the
"703
is an error.
With
–xl[d]
, the VMS FORTRAN notation
"703
signals f77
to convert from the integer octal constant to its integer decimal equivalent, 451 in this case. In VMS FORTRAN,
"703
cannot be the start of a character constant, because VMS FORTRAN character constants are delimited by apostrophes, not quotes.
•
Backslash (
\
) as ordinary character within character constants
If the
–xl[d]
option is on, a backslash in a character string is treated as an ordinary character; otherwise, it is treated as an escape character.
•
Nonstandard form of the
PARAMETER
statement
The alternate
PARAMETER
statement syntax is allowed, if the
–xl[d]
option is on.
FORTRAN 77 Reference Manual
8
Example: VMS alternate form of
PARAMETER
statement omits the parentheses:
PARAMETER FLAG1 = .TRUE.
•
Debugging lines as comment lines or FORTRAN 77 statements (
-xld
)
The compiler interprets debugging lines as comment lines or FORTRAN 77 statements, depending on whether the
–xld
option is set. If set, they are compiled; otherwise, they are treated as comments.
Example: Debugging lines:
D
REAL A(5) / 5.0, 6.0, 7.0, 8.0, 9.0 /
DO I = 1, 5
X = A(I)**2
PRINT *, I, X
END DO
PRINT *, 'done'
END
With
-xld
, this code prints
I
and
X
. Without
-xld
, it does not print them.
•
Align structures as in VMS FORTRAN
Use this feature if your program has some detailed knowledge of how VMS structures are implemented. If you need to share structures with C, you should use the default: no
-xl
8.4 Unsupported VMS FORTRAN
Most VMS FORTRAN extensions are incorporated into the f77
compiler. The compiler writes messages to standard error for any unsupported statements in the source file. The following is a list of the few VMS statements that are not supported.
•
DEFINE FILE
statement
•
DELETE
statement
•
UNLOCK
statement
VMS Language Extensions
439
8
440
•
FIND
statement
•
REWRITE
statement
•
KEYID
and key specifiers in
READ
statements
•
Nonstandard
INQUIRE
specifiers
•
CARRIAGECONTROL
•
DEFAULTFILE
•
KEYED
•
ORGANIZATION
•
RECORDTYPE
•
Nonstandard
OPEN
specifiers
•
ASSOCIATEVARIABLE
•
BLOCKSIZE
•
BUFFERCOUNT
•
CARRIAGECONTROL
•
DEFAULTFILE
•
DISP[OSE]
•
EXTENDSIZE
•
INITIALSIZE
•
KEY
•
MAXREC
•
NOSPANBLOCKS
•
ORGANIZATION
•
RECORDTYPE
•
SHARED
•
USEROPEN
•
The intrinsic function,
%DESCR
•
The following parameters on the
OPTIONS
statement:
•
[NO]G_FLOATING
•
[NO]F77
•
CHECK=[NO]OVERFLOW
•
CHECK=[NO]UNDERFLOW
•
Some of the
INCLUDE
statement
Some aspects of the
INCLUDE
statement are converted. The
INCLUDE statement is operating system–dependent, so it cannot be completely converted automatically. The VMS version allows a module-name and a
LIST
control directive that are indistinguishable from a continuation of a
FORTRAN 77 Reference Manual
8
UNIX file name. Also, VMS ignores alphabetic case, so if you are inconsistent about capitalization, distinctions are made where none are intended.
•
Getting a long integer—expecting a short
In VMS FORTRAN, you can pass a long integer argument to a subroutine that expects a short integer. This feature works if the long integer fits in 16 bits, because the VAX addresses an integer by its low-order byte. This feature does not work on SPARC systems.
•
Those VMS system calls that are directly tied to that operating system
•
Initializing a common block in more than one subprogram
•
Alphabetizing common blocks so you can rely or depend on the order in which blocks are loaded. You can specify the older with the
-M
mapfile
option to ld
.
•
If you use the defaults for both of the following:
•
The
OPEN
option
BLANK=
•
The
BN
/
BZ
/
B
format edit specifiers then formatted numeric input ignores imbedded and trailing blanks. The corresponding VMS defaults treat them as zeros.
VMS Language Extensions
441
8
442
FORTRAN 77 Reference Manual
ASCII Character Set
A
This appendix contains two tables: ASCII character sets and control characters.
443
A
Table A-1 ASCII Character Set
Dec Oct Hex Name Dec Oct Hex Name Dec Oct Hex
27
28
29
30
31
23
24
25
26
19
20
21
22
15
16
17
18
11
12
13
14
7
8
9
10
5
6
3
4
0
1
2
1B
1C
1D
1E
1F
17
18
19
1A
13
14
15
16
0F
10
11
12
0B
0C
0D
0E
07
08
09
0A
00
01
02
03
04
05
06
ETB
CAN
EM
SUB
ESC
FS
GS
RS
US
SI
DLE
DC1
DC2
DC3
DC4
NAK
SYN
VT
FF
CR
SO
BEL
BS
HT
LF
NUL
SOH
STX
ETX
EOT
ENQ
ACK
027
030
031
032
033
034
035
036
037
017
020
021
022
023
024
025
026
007
010
011
012
013
014
015
016
000
001
002
003
004
005
006
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
040
041
042
043
044
045
046
047
050
051
052
053
054
055
056
057
060
061
062
063
064
065
066
067
070
071
072
073
074
075
076
077
20
21
22
23
24
25
26
27
28
29
2A
2B
2C
2D
2E
2F
30
31
32
33
34
35
36
37
38
39
3A
3B
3C
3D
3E
3F
SP
!
"
#
$
%
&
’
(
)
*
+
,
–
.
/
0
1
2
3
4
5
6
7
8
9
:
;
<
=
>
?
92
93
94
95
88
89
90
91
84
85
86
87
80
81
82
83
76
77
78
79
72
73
74
75
68
69
70
71
64
65
66
67
130
131
132
133
134
135
136
137
120
121
122
123
124
125
126
127
110
111
112
113
114
115
116
117
100
101
102
103
104
105
106
107
5B
5C
5D
5E
5F
57
58
59
5A
50
51
52
53
54
55
56
4C
4D
4E
4F
48
49
4A
4B
44
45
46
47
40
41
42
43
119
120
121
122
123
124
125
126
127
111
112
113
114
115
116
117
118
103
104
105
106
107
108
109
110
96
97
98
99
100
101
102
Name Dec Oct Hex Name
]
^
[
\
_
Y
Z
W
X
U
V
S
T
Q
R
O
P
M
N
K
L
I
J
G
H
E
F
C
D
@
A
B
167
170
171
172
173
174
175
176
177
157
160
161
162
163
164
165
166
147
150
151
152
153
154
155
156
140
141
142
143
144
145
146
7B
7C
7D
7E
7F
77
78
79
7A
73
74
75
76
6F
70
71
72
6B
6C
6D
6E
67
68
69
6A
60
61
62
63
64
65
66 y z w x
{
|
}
~
DEL u v s t q r o p m n k l i j g h e f c d
‘ a b
444
FORTRAN 77 Reference Manual
A
^
=Control key s^=Shift and control keys
20
21
22
23
16
17
18
19
8
9
10
11
12
13
14
15
6
7
4
5
Dec
2
3
0
1
28
29
30
31
24
25
26
27
127
Table A-2 Control Characters
020
021
022
023
024
025
026
027
004
005
006
007
010
011
012
013
014
015
016
017
Oct
000
001
002
003
030
031
032
033
034
035
036
037
177
14
15
16
17
10
11
12
13
04
05
06
07
Hex
00
01
02
03
08
09
0A
0B
0C
0D
0E
0F
1C
1D
1E
1F
18
19
1A
1B
7F
FS
GS
RS
US
DEL
DC4
NAK
SYN
ETB
CAN
EM
SS
ESC
BS
HT
LF
VT
EOT
ENQ
ACK
BEL
Name
NUL
SOH
STX
ETX
FF
CR
SO
SI
DLE
DC1
DC2
DC3 s^L s^M s^N s^O s^0
^T
^U
^V
^W
^X
^Y
^Z s^K
^D
^E
^F
^G
^H
^I
^J
^K
Keys
s^P
^A
^B
^C
^L
^M
^N
^O
^P
^Q
^R
^S
Meaning
Null or time fill character
Start of heading
Start of text
End of text (EOM)
End of transmission
Enquiry (WRU)
Acknowledge (RU)
Bell
Backspace
Horizontal tab
Line feed (newline)
Vertical tab
Form Feed
Carriage Return
Shift Out
Shift In
Data link escape
Device control 1 (X-ON)
Device control 2 (TAPE)
Device control 3 (X-OFF)
Device control 4 (TAPE)
Negative acknowledge
Synchronous idle
End of transmission blocks
Cancel
End Of medium
Special sequence
Escape (
^ [
)
File separator (
^ \
)
Group separator (
^ ]
)
Record separator (
^ ‘
)
Unit separator (
^ /
)
Delete or rubout (
^ _
)
ASCII Character Set
445
A
446
FORTRAN 77 Reference Manual
Sample Statements
B
I
U
C
CA
R
This appendix shows a table that contains selected samples of the f77 statement types. The purpose is to provide a quick reference for syntax details of the more common variations of each statement type.
In the table, the following conventions are used:
Character variable
Character array
Integer variable
External unit
Real variable
S
♦
N
L
Numeric variable
Logical variable
Switch variable
Nonstandard feature
447
B
Name
ACCEPT
♦
ASSIGN
ASSIGNMENT
AUTOMATIC
♦
BACKSPACE
BLOCK DATA
BYTE
♦
CALL
CHARACTER
CLOSE
COMMON
Table B-1 FORTRAN 77 Statement Samples
Examples
ACCEPT *, A, I
ASSIGN 9 TO I
C = 'abc'
C = "abc"
C = S // 'abc'
C = S(I:M)
L = L1 .OR. L2
L = I .LE. 80
N = N+1
X = '7FF00000'x
CURR = NEXT
NEXT.ID = 82
AUTOMATIC A, B, C
AUTOMATIC REAL P, D, Q
IMPLICIT AUTOMATIC REAL (X-Z)
BACKSPACE U
BACKSPACE( UNIT=U, IOSTAT=I, ERR=9 )
BLOCK DATA
BLOCK DATA COEFFS
BYTE A, B, C
BYTE A, B, C(10)
BYTE A /'x'/, B /255/, C(10)
CALL P( A, B )
CALL P( A, B, *9 )
CALL P( A, B, &9 )
CALL P
CHARACTER C*80, D*1(4)
CHARACTER*18 A, B, C
CHARACTER A, B*3 /'xyz'/, C /'z'/
CLOSE ( UNIT=I )
CLOSE( UNIT=U, ERR=90, IOSTAT=I )
COMMON / DELTAS / H, P, T
COMMON X, Y, Z
COMMON P, D, Q(10,100)
Comments
Compare to
READ
.
Character
Logical
Arithmetic
Hex
♦
♦
Compare to
RECORD
.
Initialize
A
and
B
Alternate return
Alternate return
Initialize B and C
♦
♦
448
FORTRAN 77 Reference Manual
B
Name
COMPLEX
CONTINUE
DATA
DECODE
♦
DIMENSION
Examples
Table B-1 FORTRAN 77 Statement Samples (Continued)
Comments
COMPLEX U, V, U(3,6)
COMPLEX U*16
COMPLEX U*32
COMPLEX U / (1.0,1.0) /, V /(1.0,10.0) /
100 CONTINUE
DATA A, C / 4.01, 'z' /
DATA (V(I),I=1,3) /.7, .8, .9/
DATA ARRAY(4,4) / 1.0 /
DATA B,O,X,Y /B'0011111', O'37', X'1f',
Z'1f'/
DECODE ( 4, 1, S ) V
DIMENSION ARRAY(4, 4)
DIMENSION V(1000), W(3)
Double complex
Quad complex
Initialize
U
and
V
♦
♦
♦
(SPARC)
♦
DO DO 100 I = INIT, LAST, INCR
…
100 CONTINUE
DO I = INIT, LAST
…
END DO
Unlabeled
DO
♦
DO WHILE ( DIFF .LE. DELTA )
…
END DO
DO WHILE
♦
DO 100 WHILE ( DIFF .LE. DELTA )
…
100 CONTINUE
♦
DOUBLE COMPLEX
♦
DOUBLE COMPLEX U, V
DOUBLE COMPLEX U, V
COMPLEX*16
COMPLEX
♦
♦
COMPLEX U / (1.0,1.0D0) /, V / (1.0,1.0D0) /
Initialize
U
and
V
DOUBLE PRECISION DOUBLE PRECISION A, D, Y(2)
DOUBLE PRECISION A, D / 1.2D3 /, Y(2)
REAL*
8
♦
Initialize
D
♦
ELSE ELSE
Compare to
IF
(Block)
ELSE IF
ENCODE
♦
ELSE IF
ENCODE( 4, 1, T ) A, B, C
END
END DO
♦
END
END DO
Compare to
DO
Sample Statements
449
B
Name
ENDFILE
END IF
END MAP
♦
END STRUCTURE
END UNION
♦
ENTRY
EQUIVALENCE
EXTERNAL
FORMAT
FUNCTION
GO TO
Table B-1 FORTRAN 77 Statement Samples (Continued)
Examples
ENDFILE ( UNIT=I )
ENDFILE I
ENDFILE( UNIT=U, IOSTAT=I, ERR=9 )
END IF
END MAP
END STRUCTURE
END UNION
ENTRY SCHLEP( X, Y )
ENTRY SCHLEP( A1, A2, *4 )
ENTRY SCHLEP
EQUIVALENCE ( V(1), A(1,1) )
EQUIVALENCE ( V, A )
EQUIVALENCE (X,V(10)), (P,D,Q)
Comments
Compare to
MAP
Compare to
STRUCTURE
Compare to
UNION
EXTERNAL RNGKTA, FIT
10 FORMAT(// 2X, 2I3, 3F6.1, 4E12.2, 2A6,3L2
)
10 FORMAT(// 2D6.1, 3G12.2 )
10 FORMAT( 2I3.3, 3G6.1E3, 4E12.2E3 )
X I F E A L
D G
w
10 FORMAT('a quoted string', " another", I2)
Strings
10 FORMAT( 18Ha hollerith string, I2)
10 FORMAT( 1X, T10, A1, T20, A1 )
♦
Hollerith
Tabs
10 FORMAT( 5X, TR10, A1, TR10, A1, TL5, A1 )
Tab right, left
10 FORMAT(" Init=", I2, :, 3X, "Last=", I2) :
10 FORMAT( 1X, "Enter path name ", $ ) $
10 FORMAT( F4.2, Q, 80 A1 )
10 FORMAT( 'Octal ', O6, ', Hex ' Z6 )
10 FORMAT( 3F<N>.2 )
Q
♦
Octal, hex
♦
Variable expression
♦
FUNCTION Z( A, B )
FUNCTION W( P,D, *9 )
CHARACTER FUNCTION R*4(P,D,*9 )
INTEGER*2 FUNCTION M( I, J )
GO TO 99
GO TO I, ( 10, 50, 99 )
GO TO I
Short integer
♦
Unconditional
Assigned
GO TO ( 10, 50, 99), I
Computed
450
FORTRAN 77 Reference Manual
B
Name
IF
IMPLICIT
INCLUDE
♦
INQUIRE
INTEGER
INTRINSIC
LOGICAL
Examples
Table B-1 FORTRAN 77 Statement Samples (Continued)
IF ( I -K ) 10, 50, 90
IF ( L ) RETURN
IF ( L ) THEN
N=N+1
CALL CALC
ELSE
K=K+1
CALL DISP
ENDIF
IF ( C .EQ. 'a' ) THEN
NA=NA+1
CALL APPEND
ELSE IF ( C .EQ. 'b' ) THEN
NB=NB+1
CALL BEFORE
ELSE IF ( C .EQ. 'c' ) THEN
NC=NC+1
CALL CENTER
END IF
IMPLICIT COMPLEX (U-W,Z)
IMPLICIT UNDEFINED (A-Z)
INCLUDE 'project02/header'
INQUIRE( UNIT=3, OPENED=OK )
INQUIRE( FILE='mydata', EXIST=OK )
INQUIRE( UNIT=3, OPENED=OK, IOSTAT=ERRNO )
INTEGER C, D(4)
INTEGER C*2
INTEGER*4 A, B, C
INTEGER A/ 100 /, B, C / 9 /
INTRINSIC SQRT, EXP
LOGICAL C
LOGICAL B*1, C*1
LOGICAL*1 B, C
LOGICAL*4 A, B, C
LOGICAL B / .FALSE. /, C
Comments
Arithmetic
IF
LOGICAL IF
BLOCK IF
BLOCK IF
With
Short integer
♦
♦
♦
ELSE IF
Initialize
B
♦
♦
Initialize
A
and
C
♦
Sample Statements
451
B
Name
Map
♦
NAMELIST
♦
OPEN
OPTIONS
♦
PARAMETER
PAUSE
POINTER
♦
PRAGMA
♦
PROGRAM
READ
452
Table B-1 FORTRAN 77 Statement Samples (Continued)
Examples
MAP
CHARACTER *18 MAJOR
END MAP
MAP
INTEGER*2 CREDITS
CHARACTER*8 GRAD_DATE
END MAP
NAMELIST /CASE/ S, N, D
OPEN( UNIT=3, FILE="data.test" )
OPEN( UNIT=3, IOSTAT=ERRNO )
OPTIONS /CHECK /EXTEND_SOURCE
PARAMETER (A="xyz"), (PI=3.14)
PARAMETER (A="z", PI=3.14)
PARAMETER X=11, Y=X/3
Comments
Compare to
STRUCTURE
and
UNION
♦
PAUSE
POINTER ( P, V ), ( I, X )
EXTERNAL RNGKTA, FIT !$PRAGMA C(RNGKTA, FIT) C()
directive
PROGRAM FIDDLE
PRINT *, A, I
PRINT 10, A, I
PRINT 10, M
PRINT 10, (M(I),I=J,K)
PRINT 10, C(I:K)
PRINT '(A6,I3)', A, I
PRINT FMT='(A6,I3)', A, I
PRINT S, I
PRINT FMT=S, I
List-directed
Formatted
Array
M
Implied-
DO
Substring
Character constant format
Switch variable has format number
PRINT G
READ *, A, I
READ 1, A, I
READ 10, M
READ 10, (M(I),I=J,K)
READ 10, C(I:K)
READ '(A6,I3)', A, I
Namelist
♦
List-directed
Formatted
Array
M
Implied-
DO
Substring
Character constant format
FORTRAN 77 Reference Manual
Name
REAL
RECORD
♦
RETURN
B
Examples
Table B-1 FORTRAN 77 Statement Samples (Continued)
Comments
Formatted read from a file
READ( 1, 2 ) X, Y
READ( UNIT=1, FMT=2) X,Y
READ( 1, 2, ERR=8,END=9) X,Y
READ( UNIT=1, FMT=2, ERR=8,END=9) X,Y
READ( *, 2 ) X, Y
READ( *, 10 ) M
READ( *, 10 ) (M(I),I=J,K)
READ( *, 10) C(I:K)
READ( 1, * ) X, Y
READ( *, * ) X, Y
READ( 1, '(A6,I3)') X, Y
READ( 1, FMT='(A6,I3)') X, Y
READ( 1, C ) X, Y
READ( 1, FMT=C ) X, Y
READ( 1, S ) X, Y
READ( 1, FMT=S ) X, Y
READ( *, G )
READ( 1, G )
READ( 1, END=8, ERR=9 ) X, Y
READ( 1, REC=3 ) V
READ( 1 ' 3 ) V
READ( 1, 2, REC=3 ) V
READ( CA, 1, END=8, ERR=9 ) X, Y
READ( CA, *, END=8, ERR=9 ) X, Y
READ( CA, REC=4, END=8, ERR=9 ) X, Y
REAL R, M(4)
REAL R*4
REAL*8 A, B, C
REAL*16 A, B, C
REAL A / 3.14 /, B, C / 100.0 /
RECORD /PROD/ CURR,PRIOR,NEXT
RETURN
RETURN 2
Formatted read from standard input
Array
Implied-
Substring
List-directed from file—from standard input
Character constant format
Switch variable has format number
Namelist read
♦
Namelist read from a file
Unformatted direct access
Unformatted direct access
Formatted direct access
♦
Internal formatted sequential
Internal list-directed sequential access
♦
Internal direct access
♦
♦
M
DO
Double precision
Quad precision
Standard return
Alternate return
♦
(SPARC only)
Initialize A and C
♦
♦
Sample Statements
453
B
Name
REWIND
SAVE
STATIC
♦
STOP
STRUCTURE
SUBROUTINE
TYPE
♦
UNION
♦
VIRTUAL
♦
VOLATILE
♦
WRITE
Examples
Table B-1 FORTRAN 77 Statement Samples (Continued)
Comments
REWIND 1
REWIND I
REWIND ( UNIT=U, IOSTAT=I, ERR=9 )
SAVE A, /B/, C
SAVE
STATIC A, B, C
STATIC REAL P, D, Q
IMPLICIT STATIC REAL (X-Z)
STOP
STOP "all gone"
STRUCTURE /PROD/
INTEGER*4 ID / 99 /
CHARACTER*18 NAME
CHARACTER*8 MODEL / 'XL' /
REAL*4 COST
REAL*4 PRICE
END STRUCTURE
SUBROUTINE SHR( A, B, *9 )
SUBROUTINE SHR( A, B, &9 )
SUBROUTINE SHR( A, B )
SUBROUTINE SHR
TYPE *, A, I
UNION
MAP
CHARACTER*18 MAJOR
END MAP
MAP
INTEGER*2 CREDITS
CHARACTER*8 GRAD_DATE
END MAP
END UNION
VIRTUAL M(10,10), Y(100)
VOLATILE V, Z, MAT, /INI/
WRITE( 1, 2 ) X, Y }
WRITE( UNIT=1, FMT=2 ) X, Y
WRITE( 1, 2, ERR=8, END=9 ) X, Y
WRITE( UNIT=1, FMT=2, ERR=8, END=9 ) X, Y
Alternate return
Compare to
Compare to
Formatted
♦
STRUCTURE write
to a file
454
FORTRAN 77 Reference Manual
Name
B
Examples
Table B-1 FORTRAN 77 Statement Samples (Continued)
WRITE( *, 2 ) X, Y
WRITE( *, 10 ) M
WRITE( *, 10 ) (M(I),I=J,K)
WRITE( *, 10) C(I:K)
WRITE( 1, * ) X, Y
WRITE( *, * ) X, Y
WRITE( 1, '(A6,I3)') X, Y
WRITE( 1, FMT='(A6,I3)') X, Y
WRITE( 1, C ) X, Y
WRITE( 1, FMT=C ) X, Y
WRITE( 1, S ) X, Y
WRITE( 1, FMT=S ) X, Y
WRITE( *, CASE )
WRITE( 1, CASE )
WRITE( 1, END=8, ERR=9 ) X, Y
WRITE( 1, REC=3 ) V
WRITE( 1 ' 3 ) V
WRITE( 1, 2, REC=3 ) V
WRITE( CA, 1, END=8, ERR=9 ) X, Y
WRITE( CA, *, END=8, ERR=9 ) X, Y
WRITE( CA, REC=4, END=8, ERR=9 ) X, Y
Comments
Formatted write
to stdout
Array
M
Implied-
DO
Substring
List-directed write
to a file
List-directed write
to standard output
Character constant format
Character variable format
Switch variable has format number
Namelist write
♦
Namelist write
to a file
♦
Unformatted sequential access
Unformatted direct access
Formatted direct access
Internal formatted sequential
Internal list-directed sequential access
♦
Internal direct access
♦
Sample Statements
455
B
456
FORTRAN 77 Reference Manual
Data Representations
C
Whatever the size of the data element in question, the most significant bit of the data element is always stored in the lowest-numbered byte of the byte sequence required to represent that object.
This appendix is a brief introduction to data representation. For more in-depth explanations, see the FORTRAN 77 4.0 User's Guide and the Numerical
Computation Guide.
This appendix is organized into the following sections:
Real, Double, and Quadruple Precision
Extreme Exponents
IEEE Representation of Selected Numbers
Arithmetic Operations on Extreme Values
Bits and Bytes by Architecture page 457 page 458 page 459 page 459 page 462
C.1 Real, Double, and Quadruple Precision
Real, double precision, and quadruple precision number data elements are represented according to the IEEE standard by the following form, where f is the bits in the fraction. The quad is SPARC only.
(-1)
sign
* 2
exponent-bias
*1.f
457
458
C
Table C-1 Floating-point Representation
Sign
Exponent
Fraction
Range approx.
Single
Bit 31
Bits 30–23
Bias 127
Bits 22–0
3.402823e+38
1.175494e-38
Double
Bit 63
Bits 62–52
Bias 1023
Bits 51–0
1.797693e+308
2.225074e-308
Quadruple
Bit 127
Bits 126-112
Bias 16583
Bits 111-0
3.362E-4932
1.20E+4932
C.2 Extreme Exponents
The representations of extreme exponents are as follows.
Zero (signed)
Zero (signed) is represented by an exponent of zero and a fraction of zero.
Subnormal Number
The form of a subnormal number is:
(-1)
sign
* 2
1-bias
*0.f
where f is the bits in the significand.
Signed Infinity
Signed infinity—that is, affine infinity—is represented by the largest value that the exponent can assume (all ones), and a zero fraction.
Not a Number (NaN)
Not a Number (NaN) is represented by the largest value that the exponent can assume (all ones), and a nonzero fraction.
FORTRAN 77 Reference Manual
C
Normalized
REAL
and
DOUBLE PRECISION
numbers have an implicit leading bit that provides one more bit of precision than is stored in memory. For example, IEEE double precision provides 53 bits of precision: 52 bits stored in the fraction, plus the implicit leading 1.
C.3 IEEE Representation of Selected Numbers
The values here are as shown by dbx
, in hexadecimal.
Table C-2 IEEE Representation of Selected Numbers
Value
+0
-0
+1.0
-1.0
+2.0
+3.0
+Infinity
-Infinity
NaN
Single-Precision
00000000
80000000
3F800000
BF800000
40000000
40400000
7F800000
FF800000
7Fxxxxxx
Double-Precision
0000000000000000
8000000000000000
3FF0000000000000
BFF0000000000000
4000000000000000
4008000000000000
7FF0000000000000
FFF0000000000000
7FFxxxxxxxxxxxxx
C.4 Arithmetic Operations on Extreme Values
This section describes the results of basic arithmetic operations with extreme and ordinary values. We assume all inputs are positive, and no traps, overflow, underflow, or other exceptions happen.
Data Representations
459
C
460
Table C-3 Extreme Value Abbreviations
Abbreviation
Sub
Num
Inf
NaN
Uno
Meaning
Subnormal number
Normalized number
Infinity (positive or negative)
Not a Number
Unordered
Table C-4 Extreme Values: Addition and Subtraction
Left Operand
0
Sub
Num
Inf
NaN
0
0
Sub
Num
Inf
NaN
Sub
Sub
Sub
Num
Inf
NaN
Right Operand
Num
Num
Num
Num
Inf
NaN
Inf
Inf
Inf
Inf
Read Note
NaN
In the above table, for Inf
±
Inf: Inf + Inf = Inf, and Inf - Inf = NaN.
NaN
NaN
NaN
NaN
NaN
NaN
Table C-5 Extreme Values: Multiplication
Left Operand
0
Sub
Num
Inf
NaN
Right Operand
0
0
0
0
NaN
NaN
Sub
0
0
NS
Inf
NaN
Num
0
NS
Num
Inf
NaN
Inf
NaN
Inf
Inf
Inf
NaN
In the above table, NS means either Num or Sub result possible.
NaN
NaN
NaN
NaN
NaN
NaN
FORTRAN 77 Reference Manual
C
Table C-6 Extreme Values: Division
Left Operand
0
Sub
Num
Inf
NaN
0
NaN
Inf
Inf
Inf
NaN
Sub
0
Num
Num
Inf
NaN
Right Operand
Num Inf
0
Num
Num
Inf
NaN
0
0
0
NaN
NaN
NaN
NaN
NaN
NaN
NaN
NaN
Table C-7 Extreme Values: Comparison
Left Operand
0
Sub
Num
Inf
NaN
0
=
>
>
>
Uno
Sub
<
>
>
Uno
Right Operand
Num
<
<
>
Uno
Inf
<
<
<
=
Uno
NaN
Uno
Uno
Uno
Uno
Uno
Note:
•
If either
X
or
Y
is NaN, then
X.NE.Y
is
.TRUE.
, and the others (
.EQ.
,
.GT.
,
.GE.
,
.LT.
,
.LE.
) are
.FALSE.
•
+0 compares equal to -0.
•
If any argument is NaN, then the results of
MAX
or
MIN
are undefined.
Data Representations
461
C
C.5 Bits and Bytes by Architecture
The order in which the data—the bits and bytes—are arranged differs between
VAX computers on the one hand, and SPARC computers on the other.
The bytes in a 32-bit integer, when read from address n, end up in the register as shown in the following tables.
Byte n+3
31 30 29 28 27 26 25 24
Most Significant
Table C-8 Bits and Bytes for Intel and VAX Computers
Byte n+2
23 22 21 20 19 18 17 16
Byte n+1
15 14 13 12 11 10 09 08
Byte n
07 06 05 04 03 02 01 00
Least significant
Byte n
31 30 29 28 27 26 25 24
Most Significant
Table C-9 Bits and Bytes for 680x0 and SPARC Computers
Byte n+1
23 22 21 20 19 18 17 16
Byte n+2
15 14 13 12 11 10 09 08
Byte n+3
07 06 05 04 03 02 01 00
Least significant
The bits are numbered the same on these systems, even though the bytes are numbered differently.
Following are some possible problem areas:
•
Passing binary data over the network. Use External Data Representation
(XDR) format or another standard network format to avoid problems.
•
Porting raster graphics images between architectures. If your program uses graphics images in binary form, and they have byte ordering that is not the same as for images produced by SPARC system routines, you must convert them.
•
If you convert character-to-integer or integer-to-character between architectures, you should use XDR.
•
If you read binary data created on an architecture with a different byte order, then you must filter it to correct the byte order.
See also the man
page, xdr
(3N).
462
FORTRAN 77 Reference Manual
Index
Symbols
!
, 3, 4, 10
"
, 3, 4
$
, 3, 4, 5 edit descriptor, 267
NAMELIST
delimiter, 309
%
, 3, 4
%DESCR
, 435
%FILL
, 51, 233
%LOC
, 435
%REF
, 435
%VAL
, 435
&
, 3, 4, 100, 101, 309, 435
', 435
'
, 3, 26
(e**x)-1, 381, 386
*
, 3, 4, 103, 105, 435 alternate return, 100, 101 comments, 10
+
, 3, 4, 268
,
, 3, 4
.
, 3, 4, 52
/
, 3, 4, 295, 301
//
concatenate string, 74
:
, 3, 4 array bounds, 41 character constants, 28 edit descriptor, 295 substring operator, 46
<>
, 4, 152, 154
=
, 3, 4, 87
?
, 3, 4, 313
\
, 3, 4
_
, 3, 5, 12
Numerics
0, 1, +
vertical format control, 268
A
A
format specifier, 270 abort
, 339
ACCEPT
, 85, 435 access, 253 append option in open, 189 modes, 253 options in
OPEN
, 189
SEQUENTIAL
in
OPEN
, 189 time, 410 access
, 339
ACCESS
in
OPEN
, 189
ACHAR
, 319 action for signal, change, signal
, 408
Index-463
Index-464 address assignment, pointers, 59, 200 loc
, 390 malloc
, 60, 201 adjustable array bounds, 42 alarm
, 340 alignment data types, 23 structures, as in VMS, 436, 439 summary of, 23 variables, 16 allocation of storage, 16 allowed I/O combinations, 253 alpha editing, 270 alternate octal notation, 31 return, 222, 435 ampersand, alternate return, 100, 101, 435 and
, 342 anonymous field, 51, 233
ANSI X3.9-1978 FORTRAN 77 standard, 2
AnswerBook system, xxiv apostrophe character constants, 26, 28 direct-access record, 211, 259, 435 format specifier, 265 append on open ioinit
, 374 open
, 189 arc cosh, 380, 386 cosine, 386 sine, 386 sinh, 386 tangent, 386 tanh, 380 arc tangent, 386 arguments command line, getarg
, 360 dummy, not OK in
NAMELIST list, 306 fields, 52, 220 omitted, 433 records, 52, 220 arithmetic assignment, 72 assignment statement, 91 expression, 66, 67
IF
, 162 intrinsic functions, 316 operations on extreme values, 459 operator, 66 right shift, rshift
, 342 array adjustable bounds, 42 assumed size, 43 bounds, 41 character, 42, 104 complex numbers, 113 declarators, 40 definition, 40 dimensions, 41 double-complex, 131 double-precision, 133 elements data types, 14 not OK in
NAMELIST
list, 306 input by
NAMELIST
, 312 integer, 181 names with no subscripts, 43 ordering, 45 real, 219 subscripts, 44
ASCII character set, 443 ask for namelist names, 313
ASSIGN
, 86 assignment arithmetic, 72, 91 character, 76, 77 logical, 79 statement, 87 assumed size array, 43 asterisk alternate return, 100, 435 hex and octal output, 278
FORTRAN 77 Reference Manual
audience for this manual, xxiii
AUTOMATIC
, 93 automatic structure not allowed, 94
B
B constant indicator, 35 format specifier, 266 backslash, 3, 4, 26, 436, 438
BACKSPACE
, 95 backspace character, 28 basic terms, 2 bessel, 381, 386, 388 bic
, 342 binary constants, 35 initialization, 35 operator, 66 bis
, 342 bit functions, 342 manipulation functions, 325, 333 move bits, mvbits
, 395 bit
, 342 bit and byte order, 462 bitwise and, 342 complement, 342 exclusive or, 342 inclusive or, 342 operators, 72 blank column one, 255, 302 control, 266 fields in octal or hex input, 277, 278 line comments, 10 not significant in words, 6
BLANK OPEN
specifier, 190
BLOCK DATA
, 97 initialize, 433 names, 5 block
IF
, 163 blocks allocated, 410 blocksize, 410
BN
format specifier, 266 boldface font conventions, xxv boundary for variable alignment, 16 bounds on arrays, 41 box clear, xxv indicates nonstandard, xxv
BS 6832 standard, 2
BYTE
, 98 byte and bit order, 462
BYTE
data type, 16
BZ
format specifier, 266
C
c comments, 10 directive, 11, 12
C$pragma sun unroll=
n pragma, 12
CALL
, 99 carriage control, 255, 268
$
, 267 all files, 257 blank, 0, 1, 268 first character, 268 initialize, ioinit
, 374 space,
0, 1
, 268 carriage return,
$
edit descriptor, 267 ceiling, 386 change action for signal, signal
, 408 default directory, chdir
, 345
CHAR
, 92, 319
CHARACTER data type, 16 statement, 102 character array, 42 assignment, 76, 77, 78, 92 boundary, 16 concatenate, 74
Index-465
Index-466 constant delimiter, 310
NAMELIST
, 311 constants, 26 declared length, 105 declaring the length, 104 dummy argument, 104 expression, 74 format specifier, 433 function, 92 functions, 324 get a character getc
, fgetc
, 361 join, 74 null constants, 27 operator, 74 packing, 103 put a character, putc
, fputc
, 399 set, 3 string declared length, len
, 372 strings, 104 substring, 46 valid characters in names, 5 characters, special, 4 chdir
, 345 clear bit, 342 box, xxv
CLOSE
, 105
CMPLX
, 319 colon (
:
) array bounds, 41 edit descriptor, 295 substring operator, 46 column one formatting, 255 combinations of I/O, 253 command-line argument, getarg
, 360 commas in formatted input, 290 comments, 10
!
, 10
*
, 10 blank-line, 10
C
, 10 embedded, 432 end-of-line, 10, 432
COMMON
, 5, 108, 433 complement, 342 complex array, 113 constant in
NAMELIST
, 311 constants, 28 data type, 17 statement, 110
COMPLEX*16
, 18, 29
COMPLEX*32
, 18, 29
COMPLEX*8
, 17 computed
GO TO
, 159 concatenate strings, 74 concatenation operator, 74 conditional termination control, 295 consecutive commas,
NAMELIST
, 311 operators, 434 constant expression, 81 names (symbolic constants), 5 null character constants, 27 octal, 434 radix-50, 433 typeless numeric, 434 values in
NAMELIST
, 311 constants, 25 binary, 35 characters, 26 complex, 28
COMPLEX*16
, 29
COMPLEX*32
, 29 double complex, 29 double-precision real, 33 hex, 35 integer, 30 logical, 31 octal, 35 quad complex, 29 quad real, 34 real, 32
REAL*16
, 34
REAL*4
, 32
REAL*8
, 33
FORTRAN 77 Reference Manual
typeless, 35 continuation lines, 8, 9
CONTINUE
, 113 control characters, 3, 36, 75 in assignment, 77, 92 meanings, 445 conversion by long
, short
, 390 copy
NAMELIST
, 312 process via fork
, 357 core file, 339
Courier font, xxv ctime
, convert system time to character, 414, 416 cube root, 386 current working directory, getcwd
, 363
D
d
comments, 10
D
format specifier, 284 d_acos(x)
, 380, 381 d_acosd(x)
, 380, 381 d_acosh(x)
, 380, 381 d_acosp(x)
, 380, 381 d_acospi(x)
, 380, 381 d_addran()
, 381 d_addrans()
, 381 d_asin(x)
, 380 d_asind(x)
, 380 d_asinh(x)
, 380 d_asinp(x)
, 380 d_asinpi(x)
, 380 d_atan(x)
, 380 d_atan2(x)
, 380 d_atan2d(x)
, 380 d_atan2pi(x)
, 380, 381 d_atand(x)
, 380 d_atanh(x)
, 380 d_atanp(x)
, 380 d_atanpi(x)
, 380 d_cbrt(x)
, 381 d_ceil(x)
, 381 d_erf(x)
, 381 d_erfc(x)
, 381 d_expml(x)
, 381 d_floor(x)
, 381 d_hypot(x)
, 381 d_infinity()
, 381 d_j0(x)
, 381 d_j1(x)
, 381 d_jn(n,x)
, 381 d_lcran()
, 381 d_lcrans()
, 381 d_lgamma(x)
, 381 d_log1p(x)
, 381 d_log2(x)
, 381 d_logb(x)
, 381 d_max_normal()
, 382 d_max_subnormal()
, 382 d_min_normal()
, 382 d_min_subnormal()
, 382 d_nextafter(x,y)
, 382 d_quiet_nan(n)
, 382 d_remainder(x,y)
, 382 d_rint(x)
, 382 d_scalbn(x,n)
, 382 d_shufrans()
, 381 d_signaling_nan(n)
, 382 d_significand(x)
, 382 d_sin(x)
, 382 d_sincos(x,s,c)
, 382 d_sincosd(x,s,c)
, 382 d_sincosp(x,s,c)
, 382 d_sincospi(x,s,c)
, 382 d_sind(x)
, 382 d_sinh(x)
, 382 d_sinp(x)
, 382 d_sinpi(x)
, 382 d_tan(x)
, 382 d_tand(x)
, 382
Index-467
Index-468 d_tanh(x)
, 382 d_tanp(x)
, 382 d_tanpi(x)
, 382 d_y0(x)
, bessel, 382 d_y1(x)
, bessel, 382 d_yn(n,x)
, 382
DATA
, 114 data namelist syntax, 309, 313 representation double precision, 457 real number, 457 type signed infinity, 458
BYTE
, 16
CHARACTER
, 16
COMPLEX
, 17
COMPLEX*16
, 18
COMPLEX*32
, 18
COMPLEX*8
, 17
DOUBLE COMPLEX
, 18
DOUBLE PRECISION
, 18
INTEGER
, 19
INTEGER*4
, 20
LOGICAL
, 20
LOGICAL*1
, 16, 21
LOGICAL*2
, 21
LOGICAL*4
, 21 of an expression, 71 properties, 16 quad real
, 22
REAL
, 22
REAL*16
, 22
REAL*4
, 22
REAL*8
, 22 short integer, 19 types, 13 date and time, as characters, fdate
, 355 as integer, idate
, 369
DBLE
, 318
DBLEQ
, 318
DCMPLX
, 319 deallocate memory by free
, 60, 201, 357 debug statement, 439 decimal points not allowed in octal or hex input, 277 declaration field, 49, 184, 232 initialize in, 433 map, 56, 241 record, 51, 219 structure, 49 union, 56 declared length of character string, len
, 372
DECODE
, 117 default directory change, chdir
, 345 inquire options, 176 degree-based trigonometric functions, 333 delay execution, alarm
, 340 delimiter character constant, 310
NAMELIST
: $ or &, 309 descriptor, get file, getfd
, 364 device name, type, size, 410
DFLOAT
, 318 diamond indicates nonstandard, xxv differences, VMS and f77
, 431
DIMENSION
, 119 dimension arrays, 41 direct
I/O, 259
I/O record specifier, 213, 259, 435 option for access in open, 189 directives explicit parallelization, 12 general, 11 directory default change, chdir
, 345 get current working directory, getcwd
, 363
DISPOSE
option for
CLOSE
, 435
DO
, 122
DO WHILE
, 127
FORTRAN 77 Reference Manual
DOALL
directive, 12 documents on-line, xxiv dollar sign edit descriptor, 267 in names, 5
NAMELIST
delimiter, 309
DOSERIAL
directive, 12
DOSERIAL*
directive, 12
DOUBLE COMPLEX
, 18, 130
DOUBLE PRECISION
, 18, 131 double quote, 436, 438 character constants, 26 preceding octal constants, 31 double spacing print, 255 double-complex arrays, 131 constants, 29 data type, 18 double-precision arrays, 133 complex, 18 complex functions, 332 data representation, 457 editing, 284 functions, 379 real constants, 33 drand
, 404
DREAL
, 318 dummy arguments not OK in
NAMELIST list, 306
E
-e
, 9
E
format specifier, 286 edit descriptor
/
, 295
:
, 295
A
, 270
D
, 284
E
, 286
F
, 288
G
, 290
I
, 274
L
, 275
P
, 292 positional, 279
Q
, 291
S
, 294
SP
, 294
SS
, 294
SU
, 294
T
, 279
X
, 279
ELSE
, 133
ELSE IF
, 134 embedded blanks, initialize, ioinit
, 374 comments, 432 empty spaces in structures, 51, 233
ENCODE
, 117, 136
END
, 137
END DO
, 138
END FILE
, 139
END IF
, 141
END MAP
, 142 end of text, 75
END STRUCTURE
, 142
END UNION
, 143 end-of-line comments, 10, 432
ENTRY
, 144 environment variables, getenv
, 364 environmental inquiry functions, 326
EOF reset status for tapeio, 424 epbase
, 326 ephuge
, 326 epmax
, 326 epmin
, 326 epmrsp
, 326 epprec
, 326 eptiny
, 326 equals statement, 87
EQUIVALENCE
, 147
ERR
INQUIRE
, 174
OPEN
specifier, 190
Index-469
Index-470
READ
, 213
WRITE
, 246 error function, 386
I/O, 252 messages, perror
, gerror
, ierrno
, 396 errors and interrupts, longjmp
, 392 escape sequences, 28 evaluation of expressions, 83 exclusive or, 342 executable statements, 7 execute an OS command, system
, 407,
413 existence of file, access
, 339 exit
, 350 exponential editing, 286 exponents not allowed in octal or hex input, 277 expression arithmetic, 66, 67 character, 74 constant, 81 evaluation, 83 logical, 78 variable format, 152 extended source lines, 9
EXTERNAL
, 149 external C functions, 12 extract substring, 46 extreme exponent data representation, 458 values for arithmetic operations, 459
F
F
format specifier, 288 f77_floatingpoint
IEEE definitions, 350 f77_ieee_environment
, 353 fdate
, 355 fgetc
, 362 field, 49 argument that is a field, 52, 220
COMMON
with a field, 52, 220 declaration, 49, 184, 232
DIMENSION
with a field, 52, 220 dimensioning in type statements, 50,
233
EQUIVALENCE
, not allowed in, 52,
220 list, 50 list of a structure, 49, 232, 233 map with a field, 57, 242 name,
%FILL
, 51, 233
NAMELIST
, not allowed in, 52, 220 offset, 51, 233 reference, 52
SAVE
, not allowed in, 52, 220 type, 51, 233 file, 191 carriage control on all files, 257 connection, automatic, ioinit
, 374 descriptor, get, getfd
, 364 get file pointer, getfilep
, 365
INQUIRE
, 173 internal, 260 mode, access
, 339 names, VMS logical, 436, 437 permissions, access
, 339 preattached, 257 properties, 173 query, 173 remove, unlink
, 429 rename, 405 scratch, 256 status, stat
, 410
FILE
,
OPEN
specifier, 188
FILE=
specifier, 433 files open, 252 filling with asterisks or spaces, hex and octal output, 278 find substring, index
, 371
FIPS 69-1 standard, 2 first character carriage control, 268
FLOAT
, 318
FORTRAN 77 Reference Manual
floating-point
Goldberg white paper, xxiv
IEEE definitions, 350 floor, 386 flush
, 356 font boldface, xxv conventions, xxv
Courier, xxv italic, xxv fork
, 357 form feed character, 28
FORM
specifier in
OPEN
, 189
FORM='PRINT'
, 255
FORMAT
, 151 format
$
, 267
/
, 295
:
, 295
A
, 270
B
, 266
BN
, 266
BZ
, 266
D
, 284 defaults for field descriptors, 265
E
, 286
F
, 288
G
, 290
I
, 274
L
, 275
n
T
, 279
O
, 276 of source line, 8
P
, 292
Q
, 291
R
, 284 read into hollerith edit descriptor, 273
S
, 294
SP
, 294 specifier, 433
SS
, 294 standard fixed, 8
SU
, 294
T
, 279 tab, 9
TL
n, 279
TR
n, 279 variable expressions, 152, 154 vertical control, 267, 268
X
, 279
Z
, 276 format specifier
"
, 283 formats, 296 runtime, 208, 212, 246, 273, 296 variable format expressions, 298 formatted
I/O, 261 output, 255 formatted I/O, 261 forms of I/O, 253
FORTRAN statements, 8 fputc
, 399
FREE
, 327 free
, 60, 201, 357
FREE()
subroutine, 60, 201 fseek
, 358 fstat
, 410 ftell
, 358
FUNCTION
, 155 function length specifier, 434 malloc
, 60, 201 names, 5 types, 14 functions bit-manipulation, 333 degree-based trigonometric, 333 double-precision, 380 double-precision complex, 332 external C, 12 integer, 335 intrinsic, 316 quadruple-precision, libm_ quadruple
, 383
Index-471
Index-472 single-precision, libm_single
, 386 type coercing, 336 zero-extend, 338
G
G
format specifier, 290 general real editing, 290 gerror
, 396 get character getc
, fgetc
, 361 current working directory, getcwd
, 363 environment variables, getenv
, 364 file descriptor, getfd
, 364 file pointer, getfilep
, 365 group id, getgid
, 368 login name, getlog
, 367 process id, getpid
, 367 user id, getuid
, 367 getarg
, 360 getc
, 361 getcwd
, 363 getenv
, 364 getfd
, 364 getfilep
, 365 getgid
, 368 getlog
, 367 getpid
, 367 getuid
, 367 gmtime
, 414 gmtime()
, GMT, 418
GO TO
, 157, 161
GO TO
assigned, 157
GO TO
unconditional, 161
GO TO
, computed, 159
Goldberg, floating-point white paper, xxiv
Greenwich Mean Time, gmtime
, 414 group, 410 group ID, get, getgid
, 368
GSA validation, 2
H
hard links, 410 hex and octal format, 276 format samples, 277 input, 277 output, 278 hexadecimal constants, 35 initialization, 35 hollerith, 91, 273 horizontal positioning, 279 host name, get, hostnm
, 368 hostnm
, 368 hyperbolic cos, 386 hyperbolic tan, 382, 388 hypotenuse, 386
I
I
format specifier, 274
I/O, 253 direct, 259 errors, 252 forms, 253 random, 259 summary, 254
-i2
, 19, 23
IACHAR
, 319 iargc
, 360
ICHAR
, 319 id, process, get, getpid
, 367 id_finite(x)
, 381 id_fp_class(x)
, 381 id_irint(x)
, 381 id_isinf(x)
, 381 id_isnan(x)
, 381 id_isnormal(x)
, 381 id_issubnormal(x)
, 381 id_iszero(x)
, 381 id_logb(x)
, 381 id_signbit(x)
, 381
FORTRAN 77 Reference Manual
IDINT
, 318
IEEE, 350, 459
754, 2 environment, 353 ieee_flags
, 353 ieee_handler
>, 353 ierrno
, 396
IF
, 162, 163, 166
IFIX
, 318 illegal
REAL
expressions, 434
IMPLICIT
, 167 implicit none data typing, 433 statement, 14 typing, 14
INCLUDE
, 170, 437 inclusive or, 342 index
, 371 initial line, 8 initialize
I/O, ioinit
, 374 in
BLOCK DATA
, 433 in
COMMON
, 433 in declaration, 433 inmax
, 373 inode, 410 input commas, 290
INQUIRE
, 173, 178 inquire by file, 178 by unit, 173, 178 options summary, 177 inquire option
ACCESS
, 175
BLANK
, 176 defaults, 176
DIRECT
, 175
ERR
, 174
EXIST
, 174
FILE
, 174
FORM
, 175
FORMATTED
, 175
IOSTAT
, 174
NAME
, 175
NAMED
, 175
NEXTREC
, 176 none for permissions, 174
NUMBER
, 175
OPENED
, 175
RECL
, 176
SEQUENTIAL
, 175
UNFORMATTED
, 175
UNIT
, 174
INT
, 318
INTEGER
, 19, 179 integer and logical, 72 arrays, 181 conversion by long
, short
, 390 editing, 274 functions, 335 logical, mixed expressions, 71 long, 31 operand with logical operator, 72 short, 31 integer constants, 30
INTEGER*2
, 19
INTEGER*4
, 20
INTEGER*8
, 20 internal files, 260 interrupts and errors, longjmp
, 392
INTRINSIC
, 181 intrinsic function malloc
, 60, 201 intrinsic functions, 332 arithmetic, 316 character, 324 environmental inquiry, 326 mathematical, 322 memory allocation and deallocation, 327 special VMS, 435 trigonometric, 320 type conversions, 318 invalid characters for data, 3 ioinit
, 257, 374
IOSTAT OPEN
specifier, 190
Index-473
Index-474 iq_finite(x)
, 384 iq_fp_class(x)
, 384 iq_isinf(x)
, 384 iq_isnan(x)
, 384 iq_isnormal(x)
, 384 iq_issubnormal(x)
, 384 iq_iszero(x)
, 384 iq_logb(x)
, 384 iq_signbit(x)
, 384
IQINT
, 318 ir_finite(x)
, 387 ir_fp_class(x)
, 387 ir_irint(x)
, 387 ir_isinf(x)
, 387 ir_isnan(x)
, 387 ir_isnormal(x)
, 387 ir_issubnormal(x)
, 387 ir_iszero(x)
, 387 ir_logb(x)
, 387 ir_signbit(x)
, 387 irand
, 404 isatty
, 428 isetjmp
, 391 ishift
, 332 italic font conventions, xxv
J
join strings, 74 jump, longjmp
, isetjmp
, 392
K
key word, 2 kill
, send signal, 378
L
L
format specifier, 275 label of statement, 3 leading spaces or zeros, hex and octal output, 278 left shift, lshift
, 342 left-to-right exception, 68 precedence, 68 len
, declared length, 105, 372 length character string, len
, 372 function length specifier, 155, 157,
434
LEN
function, 105 line of source code, 9 names, 5 string, 105 variable length records, 190, 300 libm_double
, 379 libm_quadruple
, 383 libm_single
, 385 line formats, 8 length, 9 tab-format, 8, 432 line feed, 75 link
, 388 link to an existing file, link
, 388 linked list, 206 list-directed
I/O, 301 input, 301 output, 302 output to a print file, 255 literal constant, 2 literals type
REAL*16
, 433 lnblnk
, 372
LOC
, 327 local time zone, lmtime()
, 417 location of a variable loc
, 390 scratch files, 191 log gamma, 387
LOGICAL
, 20, 182 logical assignment, 79, 91 constants, 31
FORTRAN 77 Reference Manual
editing, 275 expression, 78 expression meaning, 79 file names in the
INCLUDE
, 171 file names, VMS, 436, 437
IF
, 166 integer, mixed, 72 left shift, lshift
, 342
LOGICAL*1
data type, 16 operator precedence, 79 unit preattached, 257 units, 252
LOGICAL*1
, 21
LOGICAL*2
, 21
LOGICAL*4
, 21
LOGICAL*8
, 21 login name, get getlog
, 366 long
, 390 long integers, 31 long lines in source code, 9 longjmp
, 391 lrshft
, 332 lshift
, 342 lstat
, 410 ltime
, 414 ltime()
, local time zone, 417
M
malloc
, 60, 201
MAP
, 56, 57, 184, 241, 242 maximum number of open files, 252 positive integer, inmax
, 373 memory deallocate by free
, 357 get by malloc
, 60, 201 release by free
, 60, 201 memory allocation and deallocation functions, 327
MIL-STD-1753 standard, 2 mixed integer and logical, 71, 72 mode, 70 mixed mode, 71 mixing format of source lines, 9
M
MALLOC
, 327 mode
IEEE, 353 of file, access
, 339 modifying carriage control, 267 time, 410 mvbits
, move bits, 395
N
name login, get, getlog
, 366 of scratch file, 191 terminal port, ttynam
, 428
NAME
option for
OPEN
, 435
NAMELIST
, 185, 306, 310, 311
$, 308
&
, 309 ask for names, 313 namelist-specifier, 307
NML
=, 307 prompt for names, 313
WRITE
, 306 namelist data, 309, 313 data syntax, 310
END
, 309
I/O, 305 names, 5
NBS validation, 2 negative values, hex and octal output, 278 nested substructure, 54 newline character, 28, 75
NIST validation, 2
NML
=, 308 noncharacter runtime format specifier, 433
Index-475
Index-476 none, implicit data typing, 433 nonexecutable statements, 7 nonstandard features, indicated by diamond, xxv
PARAMETER
, 436, 438 not
, 342 notation octal alternate, 31 null character, 28 character constants, 27 data item,
NAMELIST
, 311 number of continuation lines, 9 open files, 252 numeric constant, typeless, 434
O
O constant indicator, 35 edit descriptor, 276 octal alternate notation, 31 constant, 434 constants, 35 initialization, 35 octal and hex format, 276 format samples, 277 input, 277 output, 278 off the underscores, 12 offset of fields, 51, 233 omitted arguments, 433 on-line documents, xxiv
OPEN options, 435 print file, 255 specifier
ACCESS
, 189
BLANK
, 190
ERR
, 190
FILE
, 188
FORM
, 189
IOSTAT
, 190
RECL
, 190
STATUS
, 190
UNIT
, 188 statement, 187, 191 open files, limit of, 252 operand, 66 operator, 65
**
, 66
//
concatenate string, 74
:
substring, 46 character, 74 concatenation, 74 precedence, 68 relational, 80 two consecutive operators, 68, 434 with extreme values, 459 optimization problems with pointers, 61,
202 option
DISPOSE
for
CLOSE
, 435
-e
, 9 i2
short integer, 19 long lines, 9
NAME
for
OPEN
, 435 number of continuation lines, 9
OPTIONS
, 193 or
, 342 order bit and byte, 462
OS command, execute, system
, 407, 413
P
P
edit descriptor, 292 packing character, 103 padding, 10 parallel directives, 12
PARAMETER nonstandard alternate, 436, 438 statement, 50, 195, 233 parameter name, 5
PAUSE
, 198 permissions access
function, 339
FORTRAN 77 Reference Manual
ACCESS
in
INQUIRE
, 174 perror
, 396 pid
, process id, getpid
, 367
POINTER
, 200 pointer, 58, 200 address assignment, 59, 200 address by
LOC
, 59, 203 get file pointer, getfilep
, 365 linked list, 206 not OK in
NAMELIST
list, 306 problems with optimization, 61, 202 restrictions, 61, 202 pointer-based variable, 61, 202, 306 position file by fseek
, ftell
, 358 positional edit descriptor, 279 format editing, 279 preattached files, 257 logical units, 257 precedence logical operator, 79 operators, 68 prerequisites for using this manual, xxiii
, 207 print file, 189, 255, 302 procedures, 7 process copy via fork
, 357 id, get, getpid
, 367 send signal to, kill
, 378 wait for termination, wait
, 430
PROGRAM
, 210 program, 2 names, 5 units, 7 promote types, 70 prompt conventions, xxv for namelist names, 313 properties, file, 173 protection, 410 purpose of this manual, xxiii put a character, putc
, fputc
, 399 putc
, 399
Q
Q
edit descriptor, 291 q_atan2pi(x)
, 384 q_fabs(x)
, 384 q_fmod(x)
, 384 q_infinity()
, 384 q_max_normal()
, 384 q_max_subnormal()
, 384 q_min_normal()
, 384 q_min_subnormal()
, 384 q_nextafter(x,y)
, 384 q_quiet_nan(n)
, 384 q_remainder(x,y)
, 384 q_scalbn(x,n)
, 384 q_signaling_nan(n)
, 384
QCMPLX
, 319
QEXT
, 318
QEXTD
, 318
QFLOAT
, 318
QREAL
, 318 qsort
, 401 quad complex, 18 complex constants, 29 exponent, 34 real constants, 34 real data type, 22 type
REAL*16
literals, 433 quadruple precision, See quad quadruple-precision functions, libm_ quadruple
, 383 quick sort, qsort
, 401 quote, 436, 438 character constants, 26 format specifier, 283 preceding octal constants, 31
Index-477
Index-478
R
r_acos(x)
, 386 r_acosd(x)
, 386 r_acosh(x)
, 386 r_acosp(x)
, 386 r_acospi(x)
, 386 r_addran()
, 387 r_addrans()
, 387 r_asin(x)
, 386 r_asind(x)
, 386 r_asinh(x)
, 386 r_asinp(x)
, 386 r_asinpi(x)
, 386 r_atan(x)
, 386 r_atan2(x)
, 386 r_atan2d(x)
, 386 r_atan2pi(x)
, 386 r_atand(x)
, 386 r_atanh(x)
, 386 r_atanp(x)
, 386 r_atanpi(x)
, 386 r_cbrt(x)
, 386 r_ceil(x)
, 386 r_erf(x)
, 386 r_erfc(x)
, 386 r_expml(x)
, 386 r_floor(x)
, 386 r_hypot(x)
, 386 r_infinity()
, 386 r_j0(x)
, 386 r_j1(x)
, 386 r_jn(n,x)
, 386 r_lcran()
, 387 r_lcrans()
, 387 r_lgamma(x)
, 387 r_log1p(x)
, 387 r_log2(x)
, 387 r_logb(x)
, 387 r_max_normal()
, 387 r_max_subnormal()
, 387
FORTRAN 77 Reference Manual
r_min_normal()
, 387 r_min_subnormal()
, 387 r_nextafter(x,y)
, 387 r_quiet_nan(n)
, 387 r_remainder(x,y)
, 387 r_rint(x)
, 387 r_scalbn(x,n)
, 387 r_shufrans()
, 387 r_signaling_nan(n)
, 387 r_significand(x)
, 387 r_sin(x)
, 387 r_sincos(x,s,c)
, 388 r_sincosd(x,s,c)
, 388 r_sincosp(x,s,c)
, 388 r_sincospi(x,s,c)
, 388 r_sind(x)
, 387 r_sinh(x)
, 387 r_sinp(x)
, 387 r_sinpi(x)
, 387 r_tan(x)
, 388 r_tand(x)
, 388 r_tanh(x)
, 388 r_tanp(x)
, 388 r_tanpi(x)
, 388 r_y0(x)
, bessel, 388 r_y1(x)
, bessel, 388 r_yn(n,x)
, bessel, 388
-r4
, 24 radix, 284 radix-50 constant, 433 rand
, 404 random
I/O, 259 number, 387 values, rand
, 404
READ
, 211 read character getc
, fgetc
, 361 into hollerith edit descriptor, 273
REAL
, 22, 217 expressions, illegal, 434 intrinsic, 318 real arrays, 219 constants, 32 data representation of reals, 457 editing, 284, 288
REAL*16
, 22, 34, 433
REAL*4
, 22, 32
REAL*8
, 22, 33
RECL
specifier in
OPEN
, 190 recl=1
, variable length records, 190, 300
RECORD
, 219 record, 49 argument that is a record, 52, 220 assignment, 92
AUTOMATIC
, not allowed in, 220
COMMON
with a record, 52, 220
DATA
, not allowed in, 52, 220
DIMENSION
with a record, 52
EQUIVALENCE
, not allowed in, 52,
220
NAMELIST
, not allowed in, 52, 220 not OK in
NAMELIST
list, 306
PARAMETER
, not allowed in, 220 reference, 52
SAVE
, not allowed in, 52, 220 size, unformatted, 436, 437 specifier, direct-access, 211, 259, 435 statement, 51
STATIC
, not allowed in, 220 variable length, 190, 300 recursive, 93, 156, 228 reference field, 52 record, 52 relational operator, 80 release memory by free
, 60, 201 remove a file, unlink
, 429 repeat
NAMELIST
, 312 reposition file by fseek
, ftell
, 358 representation of data, 457 requesting namelist names, 313 reset EOF status for tapeio, 424 restrictions fields, 51, 233 hex and octal output, 278
NAMELIST
, 306 names, 5 pointers, 61, 202
Q
edit descriptor, 292 records, 52, 220 structures, 50, 232 substructures, 56
RETURN
, 222 return alternate, 222, 223, 435 reverse solidus, 3, 4
REWIND
, 223 right shift, rshift
, 342 rindex
, 372 rshift
, 332, 342 runtime formats, 208, 212, 246, 273, 296,
298
S
S
edit descriptor, 294 same line response, 268 sample statements, 447
SAVE
, 225 scale control, 292 factor, 292 scratch files, 191, 256
SCRATCH
option for
OPEN
, 191 secnds
, system time, 406 send signal to process, kill
, 378
SEQUENTIAL
option for
ACCESS
in
OPEN
, 189 setbit
, 342 setjmp
, See isetjmp short integer data type, 19 integers, 31
Index-479
Index-480 short
, 390 sign control, 294 signal
, 408 signal a process, kill
, 378 signals, IEEE, 353 signed infinity data representation, 458 signs not allowed in octal or hex input, 277 sine, 387 single spacing, 255 single-precision functions, libm_ single
, 386 size of character string, 105
SIZEOF
, 327 sizes, summary of, 23 skip
NAMELIST
, 312 tape I/O files and records, 424 slash, 3, 4 editing, 295 list-directed input, 301 sleep
, 409 slew control, 255, 268
SNGL
, 318
SNGLQ
, 318 solidus, 3, 4 sort quick, qsort
, 401 source line formats, 8 lines long, 9 tab-format, 432
SP
edit descriptor, 294 space, 3, 4, 6, 268 spaces, leading, hex and octal output, 278 special characters, 3, 4, 28
SS
edit descriptor, 294 standard conformance to standards, 2 fixed format source, 8 units, 252 start of heading and text, 75 stat
, 410 statement, 2, 7 function, 226 label, 3 list of all statements, 8 samples, 447
STATIC
, 229 status file, stat
, 410
IEEE, 353 termination, exit
, 350
STATUS OPEN
specifier, 190 stderr
, 252 stdin
, 252 stdout
, 252
STOP
, 230 storage allocation, 16 string assignment, 76 concatenate, 74 in list-directed I/O, 304 join, 74 length, len
, 372
NAMELIST
, 310 stroke, 3, 4
STRUCTURE
, 231 structure, 48 alignment, VMS, 436, 439 dummy field, 51, 233 empty space, 51, 233 name, 49, 50, 232, 233 nested, 54 not allowed as a substructure of itself, 56 not OK in
NAMELIST
list, 306 restrictions, 50 substructure, 54 syntax, 49 union, 56, 241
SU
edit descriptor, 294 subprogram names, 5
SUBROUTINE
, 235 subscript arrays, 44
FORTRAN 77 Reference Manual
expressions, 44 substring, 46 find, index
, 371
NAMELIST
, 310 not OK in
NAMELIST
list, 306 substructure, 54 map, 56, 241 union, 56, 241 successive operators, 68 summary data types, 23
I/O, 254 inquire options, 177 suppress carriage return, 267 suspend execution for an interval, sleep
, 409 symbolic constant name, 5 link to an existing file, symlink
, 388 name, 2, 5 symlnk
, 388 syntax field Reference, 52
INQUIRE
statement, 173 maps, 56, 241
NAMELIST input, 308 input data, 309, 313 output, 307 statement, 305
OPEN
statement, 187 record reference, 52 records, 51, 219 structure, 49, 231 unions, 56, 241 system
, 407, 413 system time secnds
, 406 time
, 414
T
T
edit descriptor, 279 tab, 3, 4 character, 28 control, 279 format source, 9, 432 tangent, 388 tape I/O, 419 close files, 420 open files, 419 read from files, 422 reset EOF status, 424 rewind files, 423 skip files and records, 424 write to files, 421 tarray()
values for various time routines, 418 tclose
, 419 temporary files, 191 terminal
I/O, 268 port name, ttynam
, 428 terminate wait for process to terminate, wait
, 430 with status, exit
, 350 write memory to core file, 339 termination control edit descriptor, 295 terms, 2 time in numerical form, 369 secnds
, 406 time(t) standard version, 414
VMS version, 415 time
, get system time, 414
TMPDIR
environment variable, 191 top of page, 255 topen
, 419 trailing blanks, initialize, ioinit
, 374 tread
, 419 trewin
, 419 triangle as blank space, xxv tskipf
, 419 tstate
, 419 ttynam
, 428
Index-481
Index-482 two consecutive operators, 434 twrite
, 419
TYPE
, 237, 435 type coercing functions, 336 field names, 51, 233
REAL*16
, 433
type, 238 typeless constants, 35 numeric constant, 434 types, 13, 23 array elements, 14 files, 253 functions, 14 summary of, 23
U
unary + or -, 434 unary operator, 67 unconditional
GO TO
, 161 underscore do not append to external names, 12 external names with, 12 names with, 5 unformatted
I/O, 298 record size, 436, 437
UNION
, 241 union declaration, 56, 241 unit, logical unit preattached, 257
UNIT
,
OPEN
specifier, 188 unlink
, 429 user, 410 user ID, get, getuid
, 367
V
valid characters for data, 5 characters in character set, 3 characters in names, 5 values, extreme for arithmetic operations, 459 variable alignment, 16 boundary, 16 name, 5 variable formats, 152, 154, 208, 212, 246,
263, 273, 296, 297, 298 variable-length records, 190, 300 variables, 39 vertical format control, 255
$
, 267 space,
0
,
1
,
+
, 268 vertical tab character, 28
VIRTUAL
, 243, 433
VMS FORTRAN align structures, 436 features with
-xl backslash, 5, 28, 303, 438
D
or d
debug lines, 10 debugging lines, 439 logical file names, 171, 436, 437 parameter form, 195, 197, 438 quotes, 90 octal notation, 31, 438 unavailable for strings, 16,
26 record length, 190, 437 features with
-xl record length, 176 unsupported extensions, 439
VOLATILE
, 243
W
wait
, 430 width defaults for field descriptors, 265 word boundary, 16
WRITE
, 244 write a character putc
, fputc
, 399
FORTRAN 77 Reference Manual
X
X constant indicator, 35 edit descriptor, 279
-xl
, 10, 16, 26, 28, 31, 90, 195, 435, 436, 438
-xld
, 439 xor
, 342
Y
y0(x), y1(x), y(n)
, bessel, 388 y0(x), y1(x), yn(x)
, bessel, 382
Z
Z constant indicator, 35 edit descriptor, 276 zero, leading, in hex and octal output, 278 zero-extend functions, 338
Index-483
Index-484
FORTRAN 77 Reference Manual
Index-485
Copyright 1995 Sun Microsystems Inc., 2550 Garcia Avenue, Mountain View, Californie 94043-1100 U.S.A.
Tous droits réservés. Ce produit ou document est protégé par un copyright et distribué avec des licences qui en restreignent l’utilisation, la copie, et la décompliation. Aucune partie de ce produit ou de sa documentation associée ne peuvent Être reproduits sous aucune forme, par quelque moyen que ce soit sans l’autorisation préalable et écrite de Sun et de ses bailleurs de licence, s’il en a.
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Key features
Comprehensive FORTRAN 77 language guide
Detailed explanation of data types and items
Covers arithmetic, character, and logical expressions
Extensive documentation on FORTRAN statements
Includes specifics on formatted and unformatted I/O
Lists intrinsic and library functions
Supports VMS language extensions
Describes source line formats and character sets
Addresses data representation and memory management
Frequently asked questions
The FORTRAN 77 4.0 Reference Manual discusses Standard Fixed Format and Tab-Format for source lines, detailing the structure for statements, labels, and continuation indicators.
A continuation line in FORTRAN 77 is indicated by placing any character other than a blank or a zero in column 6 of the source line.
FORTRAN 77 supports various fundamental data types including Integer, Real, Double Precision, Complex, Double Complex, Logical, Byte, and Character, each with specific properties and sizes.
