Phase One Systems BASIC software Reference Manual

PDF

مستند

BASIC

LANGUAGE

REFERENCE

MANUAL

OPERATING SYSTEM SOFTWARE

MAKES MICROS RUN LIKE MINIS

From

PHASE ONE SYSTEMS, INC.

OAKLAND, CALIFORNIA

BASIC

LANGUAGE

REFERENCE

MANUAL

Second Edition

Documentation by: C. P. Williams

Software by: Timothy S. Williams

OPERATING SYSTEM SOFTWARE

MAKES MICROS RUN LIKE MINIS

From

PHASE ONE SYSTEMS, INC.

OAKLAND, CALIFORNIA

7700 Edgewater Drive, Suite 830

Oakland, California 94621

Telephone (415) 562-8085

TWX 910-366-7139

Second edition, First printing: March, 1980

PROPRIETARY NOTICE

The software described in this manual is a proprietary product developed by Timothy

S. Williams and distributed by Phase One Systems, Inc., Oakland, California. The product is furnished to the user under a license for use on a single computer system and may be copied (with inclusion of the copyright notice) only in accordance with the terms of the license.

Previous editions copyright 1978, 1979, and 1980 by Phase One Systems, Inc. All rights reserved. Except for use in a review, the reproduction or utilizati~n of this work in any form or by any electronic, mechanical, or other means, now known or hereafter invented, including xerography, photocopying, and recording, and in any information storage and retrieval system is forbidden without the written permission of the publisher.

Z80 is a registered trademark of Zilog, Incorporated.

BASIC is a registered trademark of the Trustees of Dartmouth College.

PREFACE

This manual describes the OASIS BASIC programming language interpreter/compiler available with the OASIS Operating System.

It is intended to be a reference manual, that is, the user is assumed to have general programming skills. When this is the case this manual can instruct the user on the features and uses of OASIS BASIC.

The OASIS BASIC language conforms to, and is an extension of, the American National

Standard for Minimal BASIC, BSR X3.60.

The experienced BASIC programmer may find the appendices sufficient for his use.

However, OASIS BASIC offers many features not found in standard Dartmouth BASIC,

ANSI minimal BASIC or other dialects of BASIC.

This manual, named BASIC, like all OASIS documentation manuals, has the manual name and revision number in the lower, inside corner of each page of the body of the manual. In most chapters of the manual the last primary subject being discussed on a page will be identified in the lower outside corner of the page.

Related Documentation

The following publications provide additional information that may be required in the use of the OASIS BASIC language:

OASIS System. Reference Manual

OASIS Text Editor Reference Manual

OASIS EXEC Language Reference Manual

OASIS MACRO AsseJabler Language Reference Hanual

- iii -

TABLE OF CONTENTS

Section Page

CHAPTER 1

1.1

INTRODUCTION

· ..................................................... .

Organization of This Manual •••••••••••••••••••••••••••••••••••••••••••

1.2

1.3

1.4

1.5

1.6

Documentation Standards •••••••••••••••••••••••••••••••••••••••••••••••

BASIC Command Modules

BASIC Program File Types

Loading BASIC

.........................................................

BASIC and RUN Commands

· .............................................. .

CHAPTER 2

2.1

FEATURES OF THE LANGUAGE

Data Files

...........................................

2.2

2.3

Cursor Control ••••••••••••••••••••••••••••••••••••••••••••••••••••••••

Chaining and Linking ••••••••••••••••••••••••••••••••••••••••••••••••••

2.4

2.5

2.6

User Defined Control Keys •••••••••••••••••••••••••••••••••••••••••••••

Compatibility

Other Features

........................................................

CHAPTER 3

3.1

3.2

3.3

3.4

BECOMING FAMILIAR WITH BASIC

Some Basic BASIC Concepts

BASIC Uses Upper Case

Typing to BASIC

Consistency in Listing

.......................................

CHAPTER 4 PROGRAMMING IN BASIC

...............................................

4.1 Structure of a BASIC Program ••••••••••••••••••••••••••••••••••••••••••

4.1.1 Syn tax . . . . . . . . . • . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . .

4.1.2

4.1.3

Character Set •••••••••••••••••••••••••••••••••••••••••••••••••••• ......................................................

4.2 Statements

4.3

4.4

Line Format ............................................................

4.2.1 Single Statement~ Multi-Statement Lines

Line Labels

..........................

Documenting Procedures ••••••••••••••••••••••••••••••••••••••••••••••••

4.5 Entering and Modifying Programs •••••••••••••••••••••••••••••••••••••••

CHAPTER 5 ELEMENTS OF THE BASIC LANGUAGE

5.1 Constants

5.1.1 Numeric Constants

5.1.2 Integer Constants

5.3

5.1.3 String Constants

5.2 Variables

5.2.1

5.2.2

5.2.3

Numeric Variables

Integer Variables

String Variables

Array Variables

5.4 Functions

5.4.1

Intrinsic Functions

5.4.2

..............................................

User Defined Functions •••••••••••••••••••••••••••••••••••••••••••

5.4.3 USR Func t ions ••••••••••••••••••••••••••••••••••••••••••••••••••••

5.5 Expressions

...........................................................

5.5.1 Arithmetic Expressions •••••••••••••••••••••••••••••••••••••••••••

5.5.2 String Expressions •••••••••••••••••••••••••••••••••••••••••••••••

5.5.3 Logical Expressions ••••••••••••••••••••••••••••••••••••••••••••••

- i v -

TABLE OF COJITEHTS

Sect:l.on

5.5.4

5.5.5

Relational Expressions •••••••••••••••••••••••••••••••••••••••••••

Expression Evaluation ••••••••••••••••••••••••••••••••••••••••••••

CHAPTER 6

6.1 Numeric Field Masks

....................................................

6. f.1

FORMATED OUTPUT ...................................................

Specifying Number of Digits

6.1.2

6.1.3

Decimal Point Specification

Comma Specification

.................................... .

6.1.4

6.1.5

6.1.6

6.1.7

6.1.8

Dollar Field Specification

Asterisk Fill Specification

· .................................... .

Sign Specification

...............................................

Exponential Field Specification

Field Specification too Small

6.2 String Field Masks

....................................

6.2.1

6.2.2

6.2.3

6.2.4

Single Character

Left Justified Field

Right Justified Field

Center Justified Field

· ........................................... .

...........................................

Extended Field •••••••••••••••••••••••••••••••••••••••••••••••••••

6.3

6.4

6.5

6.2.5

Multiple Fields In One Mask

Re-using Mask Fields

Using Errors

...........................................

........................................................ .

CHAPTER

7.1

7.2

7.3

7 USING FILES

Access Mode

· ...................................................... .

Access Methods ••••••••••••••••••••••••••••••••••••••••••••••••••••••••

7.4

7.5

File Formats ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••

Record Allocation Requirements ••••••••••••••••••••••••••••••••••••••••

Multi-User File Protections •••••••••••••••••••••••••••••••••••••••••••

CHAPTER 8

8.1

8.2

8.3

8.4

8.5

8.6

8.7

8.8

8.9

8.10

8.11

8.12

COMMANDS

AUTO Command

BREAK Command

...........................................................

Bottom Command

CHANGE Command

CONTINUE Command

DELETE Command

Down Command

HELP Command

INDENT Command

LENGTH Command

LIST Command

LOAD Command

8.13 LOCATE Command

8.14

8.15

8.16

8.17

LPLIST Command

LPXREF Command

MODIFY Command

N.AM.E

Command •••••••••••••••••••••••••••••••••••••••••••••••••••••••••

8.18

8.19

8.20

8.21

NEW Command

QUIT Command

· ........................................................ .

RENUMBER Command

RUN Command

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Page

TABLE OF CONTENTS

Section Page

8.22

8.23

8.24

8.25

8.26

8.27

8.28

8.29

SAVE Command

STEP Command

Top Command

....................................................... .

TRACE and UNTRACE Commands

UNBREAK Command

Up Command •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••

VARS Command

XREF Command

· ....................................................... .

CHAPTER

9.1

9.2

9.3

9.4

9.5

9.6

9.7

9.8

9.9

9.10

9.11

9.12

9.13

9.14

9.15

9.16

9.17

9.18

9.19

9.20

9.21

9.22

9.23

9.24

9.25

9.26

9.27

9.28

9.29

9.30

9.31

9.32

9.33

9.34

9.35

9.36

9.37

9.38

9.39

9.40

9.41

9.42

9 STATEMENTS

CASE Statement

CEND Statement

· ...................................................... . 97

101

CHAIN Statement

CLEAR Statement

CLOSE Statement

COMMON Statement

CSI Statement

DATA Statement

DEF Statement •••••••••••••••••••••••••••••••••••••••••••••••••••••••••

DELETE Statement

· ................................................... .

DIM Statement ••••••••••••••••••••••••• ~ ••••••••••••••••••••••••••••••

ELSE Statement

END Statement

FNEND Statement

FOR Statement

GET Statement

GOSUB Statement

GOTO Statement

IF Statement

IFEND Statement

INPUT Statement

102

104

105

106

107

108

109

112

113

114

115

116

117

120

122

124

125

127

128

LET Statement

LINK Statement

LINPUT Statement

LINPUT USING Statement

MAT Statement

130

134

136

138

141

MAT INPUT Statement

MAT PRINT Statement

MAT READ Statement

................................................ .

MAT WRITE Statement

MOUNT Statement

NEXT Statement

ON ERROR Statement

142

144

146

148

150

151

153

ON GOSUB and ON GO TO Statements

OPEN Statement

OPTION Statement

OTHERWISE Statement

PRINT Statement ••••••••••••••••••••••••••••••••••••••••••••••••••••••

PRINT USING Statement

PUT Statement

QUIT Statement

RANDOMIZE Statement

155

157

161

163

164

168

170

172

173

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TABLE OF CONTENTS

Secti.on Page

9.43

9.44

9.45

9.46

9.47

9.48

9.49

9.50

9.51

9.52

9.53

9.54

9.55

9.56

9.57

9.58

READ Statement •••••••••••••••••••••••••••••••••••••••••••••••••••••••

READNEXT Statement

...................................................

REM Statement

RESTORE Statement

RESUME Statement

174

176

178

179

180

RETURN Statement ••••••••••••••••••••••••••••••••••••••••••••••••••••• 182

RUN Statement ••••••••••••••••••••••••••••••••••••••••••••••••••••••••

SELECT Statement

SLEEP Statement

STOP Statement

.....................................................

.......................................................

THEN Statement •••••••••••••••••••••••••••••••••••••••••••••••••••••••

184

186

187

188

189

UNLOCK Statement ••••••••••••••••••••••••••••••••••••••••••••••••••••• 190

WAIT Statement •••••••••••••••••••••••••••••••••••••••••••••••••••••••

WEND Statement

WHILE Statement

WRITE Statement

....................................................... 191

193

194

196

CHAPTER

10.1

10.2

10.3

10.4

10.5

10.6

10.7

10.8

10 FUNCTIONS

Numeric Functions

· .................................................. .

Trigonometric Functions ••••••••••••••••••••••••••••••••••••••••••••••

199

201

206

String Functions ••••••••••••••••••••••••••••••••••••••••••••••••••••• 208

Input/Output Functions ••••••••••••••••••••••••••••••••••••••••••••••• 214

Logical Functions •••••••••••••••••••••••••••••••••••••••••••••••••••• 215

File Function ••••••••••••••••••••••••••••••••••••••••••••••••••••••••

Error Functions ••••••••••••••••••••••••••••••••••••••••••••••••••••••

216

USR Function •••••••••••••••••••••••••••••••••••••••••••••••••••••••••

217

218

APPENDIX A RESERVED WORDS •••••••••••••••••••••••••••••••••••••••••••••••••••• 219

APPENDIX B USER DEFINABLE KEYS

...............................................

Control Key Values ••••••••••••••••••••••••••••••••••••••••••••••••••••

220

221

APPENDIX C COMMAND SUMMARY

APPENDIX D STATEMENT SUMMARY

223

.................................................

225

APPENDIX E FUNCTION SUMMARY 229

APPENDIX F ERROR MESSAGES

F.1

· .................................................. .

Command Errors ••••••••••••••••••••••••••••••••••••••••••••••••••••••••

233

F.2

F.3

Edit Errors •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••

Compile Errors ••••••••••••••••••••••••••••••••••••••••••••••••••••••••

234

F.4 Execution Errors •••••••••••••••••••••••••••••••••••••••••••••••••••••• 235

APPENDIX G PROGRAM EXAMPLES

G.1 Example

..................................................

One •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••

239

G.2

G.3

G.4

G.5

G.6

G.7

Example

Two String Conversion •••••••••••••••••••••••••••••••••••••••

Three - Sine Wave •••••••••••••••••••••••••••••••••••••••••••••

239

240

Four - Bill of Materials ••••••••••••••••••••••••••••••••••••••

Five ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••

Six - Sequential File I/O

.....................................

Seven - Indexed File I/O - Sequential Access

..................

241

242

244

245

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TABLE 01' COI!ITEITS

Sect~on Page

G.8 Example Eight - Indexed File Create ••••••••••••••••••••••••••••••••••• 246

- viii -

CHAPTER. 1

INTK.ODUcnOH

This reference manual describes the BASIC language as implemented in the OASIS

Operating System. It is an interpreter/compiler language. This means that the advantages of an interpreter exist (ability to make changes to the source program and immediately re-execute, immediate mode, etc.) along with the advantages of a compiler (faster execution, smaller program size on disk and in memory, and source program protection).

1.1 Organization of This Hannal

This manual discusses each command or statement in a separate section of the appropriate chapter ("COMMANDS", "STAT.EMENTS", or "FUNCTIONS").

Each command or statement is described in four subsections:

1. General form: defines the specific syntax of the statement or command. This section is enclosed in a box at the top of the page.

Also included here is a "See also" reference listing commands or statements that have a similar or related function and might be used instead of the command or statement specified.

2. Purpose: one or two sentences that summarize the purpose or general function of the statement or command.

3. Comment: detailed description of the statement or command specifying any restrictions, exceptions or errors that may occur.

4. Examples: general examples command, if applicable. meaningful. of the various forms of the statement or

Invalid examples are also included, if

In addition, the appendices at the end of this manual give summaries of the statements, commands, functions, error messages and some general examples of BASIC programs.

1.2 Documentation Standards

In this documentation, the following standards will be used:

All verbs are spelled out even though BASIC only requires the first three characters of a verb.

Fields enclosed with angle brackets <> are required for correct BASIC syntax-

Fields enclosed with brackets [] are optional and not required for valid syntax.

Fields grouped in vertical columns or separated by vertical bars indicate that all are valid forms.

Any parenthesis shown are required for valid syntax-

The term <CR> indicates the entry of the key CARRIAGE RETURN.

BASIC - 1 -

BASIC JlEI'ERENCE MANUAL

1.3 BASIC Command Modules

The OASIS BASIC and RUN programs are held on disk in seven separate files. This is required due to the fact that program overlays are used. The five files containing the BASIC program must all reside on one disk. The two files containing the RUN program must both reside on one disk. The files and their primary functions are as follows:

BASIC.COMMAND

BASIC.OVERLAYl

BASIC.OVERLAY2

BASIC. OVERLAY 3

BASIC.OVERLAY4

Initialization and set up.

Editor and syntax analyzer.

Compiler.

Cross-reference generator.

Program execution and debugger.

RUN.COMMAND

RUN.OVERLAYl

Initialization and set up.

Run time monitor.

1.4 BASIC Program. File Types

OASIS BASIC uses three different file types for programs. These file types are

BASIC, BASICOBJ, and BASICCOM.

A BASIC program with a file type of BASIC is a file in ASCII format and is usable by TEXTEDIT and EDIT as text files. A program with a type of BASIC may be loaded with the BASIC interpreter but may not be RUN, CHAINed, or LINKed to.

A BASIC program with a file type of BASICOBJ is a file generated by the BASIC interpreter after the program has been syntax checked. This type of a file cannot be used by other system programs (except COPYFILE). A BASICOBJ file is a program that is "pseudo-compiled", that is, all keywords have been coded to reduce the storage requirements and to increase execution speed. Even though this type of a file is pseudo-compiled it is still listable by BASIC and still has all remarks, variable names and line labels in it. This file type should be used for all source programs and is the default type used by the SAVE command.

A BASIC program with a file type of BASICCOM is a file generated by the BASIC compiler after the program has been compiled. This type of file cannot be used by other system programs (except COPYFILE) and may only be executed with the RUN command. A BASICCOM file is a program that has had all remarks removed from it and all variable names have been reduced to codes (variables defined as COMMON are not affected) and all line label references have been changed to a shorted method of branching.

1.5 Loading BASIC

The BASIC command is a program module that is accessed by the Operating System through the OASIS Command String Interpreter (CSI). After CSI has displayed it's prompt character (», the operator may enter a BASIC command as described below.

CSI will load the BASIC interpreter and enter the edit mode, allowing you to load, execute, or edit any BASIC program.

In the edit mode or a numbered immediately, a time. of BASIC, acceptable input is a command, an immediate statement, statement. An immediate statement is one that is executed numbered statement is stored in memory for execution at a later

- 2 -

BASIC

CHAPTER. 1: IBTRODUCTIOB

1.6 BASIC and RUN Commands

The OASIS BASIC command allows the user to access the BASIC interpreter/compiler to create, change, debug, execute or compile BASIC programs. The format of the BASIC command is:

BASIC [<program-na.me> [( <ccmpile options> [)] ]

Where: program-name Specifies the name of a BASIC program file that the user wishes to compile. This operand has the format <fn[.ft] [:fd]>, where: fn Indicates the file name of the BASIC program to be compiled. If omitted (i.e., the entire program-name operand is omitted), then

BASIC is invoked in the immediate mode. ft Indicates the file type of the program to be compiled. Only

BASIC programs with file type BASICOBJ can be compiled. fd Indicates the label of the directory or the name of the disk that the program file resides on. When omitted the normal search sequence for user programs is used.

BASIC Compile Options

PRINTER[n] Indicates that the program listing is to be output to the printer.

TYPE Indicates that the program listing is to be output to the console.

Indicates that the cross reference table is to be generated and output with the program listing.

Note 1: Compiled programs are saved on disk with file type BASICCOM.

Note 2: The COMMON statement must be used to specify variables that are used by more than one segment of a compiled program.

Since a compiled program does not have line numbers the listing from the compiler will include the relative address of each line. These address values are in hexadecimal and are displayed during execution if an error occurs.

The OASIS RUN command allows the user to execute a compiled, BASIC programs. The format of the RUN command is:

RUN <program name>

The RUN command can only execute compiled programs--there is no immediate or command mode available to the user when this command is in control.

BASIC Prompting Character

When the BASIC interpreter/compiler is in immediate or command mode a hyphen (-) is displayed at the left side of the terminal, indicating that BASIC is awaiting a command. This is the prompting character for OASIS BASIC.

BASIC - 3 -

BASIC REnRERCE HANUAL

For example:

>BASIC

>BASIC GAMES

In the second example no prompting hyphen is displayed because the program GAMES was compiled and saved as GAMES.BASICCOM:S.

- 4 - BASIC

CHAPTER. 2

FEATURES OF THE LANGUAGE

2.1 Data Files

OASIS BASIC supports three types of files: Sequential, Direct, and Indexed

Sequential. Sequential files are character files in that they contain only ASCII characters and are generally used for print or report files. This file type can be used for INPUT or OUTPUT but cannot be updated. Records in this file type are of variable length.

DIRECT files are binary files in that they contain any information, character or otherwise. This file type requires fixed length records due to the fact that records are accessed by using their relative record number.

INDEXED Sequential files are binary files similar to DIRECT files and they have fixed length records but the records are accessed randomly or sequentially by using an ASCII key.

2.2 Cursor Control

Many types of terminals are "known" to BASIC and their various types of cursor control are handled by common functions (AT and CRT). Refer to the OASIS System

Reference Manual, "ATTACH COMMAND", and the "Terminal Class Codes" Appendix for details.

2.3 Chaining and Linking

Chaining and linking allows very large programs to be segmented for execution in a system with a relatively small amount of memory. Chaining transfers control to the named segment and closes all open files. Linking transfers control to the named segment without closing any files.

2.4 User Defined Control Keys

User programs can test whether one of several different control keys were entered as input, and take appropriate action in the program. Refer to the chapter on User

Definable Keys in this manual for details.

2.5 Compatibility

BASIC is upward compatible

American National Standard with Dartmouth BASIC information regarding this standard. and conforms for Minimal BASIC, BSR X3.60. to the proposed

Refer to Appendix H for

BASIC - 5 -

BASIC REFERENCE HARUAL

2.6 Other Features

OASIS BASIC provides many other features not normally found in other micro-computer

BASICs such as:

Multiple statements on one line.

Multiple line user defined functions (DEF FN-FNEND).

Line length of up to 255 characters.

Long variable names.

Line labels.

Error trapping (ON ERROR GOTO).

Complex IF THEN ELSE statements.

Multiple line IF-IFEND structure.

Multiple line WHILE-WEND structure.

Multiple line SELECT-CASE-CEND structure.

String handling with string length of up to 255 characters.

String arrays.

Matrix (array) input/output and assignment.

Formatted output (PRINT USING).

Formatting function.

Formatted input (LINPUT USING).

Interface to user written assembly subroutines (USR).

Interface to system commands (CSI).

Interface to any device (GET, PUT, WAIT).

Bit manipulating logical functions.

Thirteen digit precision BCD (binary coded decimal) arithmetic.

Floating point values in range lO~126 to lO~-126

Integer arithmetic (-32767 to +32767).

Program debugging aids such as single step, break-points, etc.

Automatic line number entry.

Syntax analysis on statement entry.

Extensive set of string functions.

Compile option to compress and protect the program.

Cross reference listing of variables.

6 BASIC

CBAPTEIl 3

BASIC

BECOHIBG FAHILIAR WITH BASIC

This section assumes that you have loaded BASIC and that you have received the

BASIC prompting character (-), indicating that BASIC is waiting to perform whatever instuction you give. In order to make the most efficient use of your sessions with

BASIC, you need to know several things abount communicating with the system.

For the time being the specific statement, command and line syntax will be ignored.

These concepts are discussed in the next chapter.

You will communicate with the system by using its primary input/output (I/O) device, called the CONSOLE TERMINAL. This device will include either a printing mechanism or a video screen (CRT), as well as a keyboard, similar to that found on a typical electric typewriter. On a console terminal keyboard, however, there are a few symbols and extra keys which may be new to you. Note the position of "extra" keys, especially the ones marked "CONTROL" (or "CTRL", or "CNTRL" or something similar), "RETURN" (or "CARRIAGE RETURN", or "NEW LINE" or something similar),

"RUBOUT" (or "DEL", or "BACKSPACE", or something similar), "ESC" (or "ESCAPE", or

"ALTMODE") •

3.1 Some Basic BASIC Concepts

OASIS BASIC has two modes of operation:

IMMEDIATE MODE or command mode, in which lines typed to the system are executed without delay;

EXECUTION MODE or program mode, in which the system executes instructions which have been stored previously in the form of a PROGRAM.

Prior to learning how to work with BASIC in these modes, you must understand certain concepts and terminology, which are explained in this section.

A COMMAND is a special type of BASIC instruction which may be executed in immediate mode, not as part of a program. Commands generally provide services which are not meaningful or useful while a program is executing.

For example, the command LIST generates a listing of the program currently in the

BASIC program/data area of memory. (This is called the CURRENT PROGRAM.) It is a rare application which requires a program to list itself, and so the LIST function is a command.

A STATEMENT is a BASIC instruction which may be used as part of a PROGRAM or in

IMMEDIATE MODE. Typical among statements is PRINT, which causes information to be output to the console terminal. Statements begin with a VERB from which the statement derives its name. The verb may be followed by ARGUMENTs and keywords.

An argument is a piece of information on which the statement operates, or which is used to modify the operation of the statement. For example, the string literal

''HI'' is the argument of the following statement:

PRINT "HI"

A BASIC program is structured as a sequence of LINEs, each containing one or more statements. A line starts with a LINE NUMBER, which is an INTEGER (that is, a whole number) in the range of 1 to 9999. A statement follows the line number, and the combination is called a PROGRAM LINE. A typical line is:

7 -

BASIC REFERENCE HAlmA!.

70 PRINT "THIS IS ONE STATEMENT."<CR>

More than one statement may exist on a program line, as long as individual statements on that line are separated by a backslant (\) character. Here is an example of a multiple-statement program line with three statements:

100 LET A = 0 \ LET B = 1 \ PRINT A,B

All statements may be executed in immediate mode in order to get immediate results.

This is accomplished by typing a statement without preceding it with a line number.

Such a statement is called an IMMEDIATE STATEMENT, and is executed as soon as it has been completely typed (indicated by striking the RETURN key). For example, if you type:

PRINT 3+3<CR> into BASIC, you will immediately get back 6 on the terminal. This ability to execute statements in immediate mode greatly facilitates debugging by allowing you to examine (PRINT) and modify (LET) the contents of variables when a bug occurs.

Each command and statement has its own rules as to what constitutes its proper syntax and when it can be used correctly.

3.2 BASIC Uses Upper Case

BASIC requires that the instructions it executes be in upper case characters. To facilitate this, instructions typed in BASIC are translated to upper case before being stored for execution. For example, the following line is typed to BASIC:

10 if a1 > 25 then print "Greater than" else goto 100<CR>

That line is stored in memory in the following format:

10 IF Al>25 THEN PRINT "Greater than" ELSE GOTO 100

Note that all of the "keywords" have been translated to uppercase but the literal is left as is. Because of this you will not have to worry about the case mode of the instructions you type.

3.3 Typing to BASIC

Try typing some nonsense to BASIC:

-ABCDEFGHIJK<CR>

Be sure to strike the RETURN key after you denoted by the <CR> symbol above. This is process what you've typed. If you fail to patiently wait forever for you to type more! finish typing a line to BASIC, as the signal for BASIC to accept and strike the RETURN key, BASIC will

BASIC should respond to your nonsense with the message:

Unrecognized command

In general, this message is BASIC's way of saying "I don't understand you". It usually means that you typed" the right thing incorrectly, or (as in this case) the

- 8 BASIC

CHAPTER. 3: BECOllIRG I'AHILIAR. VITH BASIC wrong thing altogether. This is an example of an ERROR MESSAGE. Such messages are sent to you in order to alert you to any difficulties which BASIC encounters as it attempts to carry out your instructions. The error message should provide a clue as to the nature of the problem, and imply the possible steps you might use to correct it. (Correcting computer problems is called "debugging". A problem itself is referred to as a "bug".)

Let's type something which BASIC will understand:

-PRINT 25/2<CR>

(Remember that the <CR> means to strike the RETURN key.)

You should get the answer displayed on the terminal.

Commands may be entered with abbreviations (such as LEN for the LENGTH command) but incorrect syntax or spelling errors will not be allowed and you will have to re-enter the command.

Statements (immediate or stored) may also use abbreviations for the statement verb

(such a PRI for PRINT). Statements, different from commands, do not have to be re-entered to correct spelling or syntax errors, just modified to the correct form.

For example, try typing the statement:

10 FOR I=lTOX<CR>

BASIC will respond by displaying:

Keyword Missing or mis-spelled

0010 FOR I=lTOX

The underscore character will be used to identify the cursor position. BASIC is

"saying" that it recognizes the statement as a FOR statement but it can't find the keyword TOX. This is due to the fact that variable names may be more than one character long and the letters TOX could be a variable name. You must surround keywords and verbs with some delimiting character, usually a space.

To correct the error in this statement, enter an I, space, <CR>, space, space, I, space, <CR>, <CR>. This is explained below.

When an error is detected by the syntax analyzer the error message is displayed as above and an implied MODIFY command is executed with the cursor pointing to the location of the error. The correction just specified causes MODIFY to go into insert mode (the I character), insert a space at that location, exit the insert mode (the <CR», advance two places (the space, space characters), go into insert mode again and insert a space, exit the insert mode, then exit the modify mode (the last <CR».

BASIC - 9 -

BASIC RERRENCE HAlfUAL

The following display illustrates this correction:

0010 FOR I=lTOX

0010 FOR 1=1 IOX

0010 FOR 1=1 TOX

0010 FOR 1=1 TO,!

0010 FOR 1=1 TO X

0010 FOR I = 1 TO X

Enter I

Enter space

Enter <CR>

Enter space

Enter I

Enter space

Enter <CR>

Enter <CR> (display command)

When you exit the implied MODIFY command the syntax of the statement is re-examined for errors. If no more errors are detected the statement is saved (or executed if an immediate statement) and control of BASIC returns to the mode it was in (in the above case it returns to the command mode).

As another example, consider the following:

-10 PRI SQR(23jNOW IS THE TIMEjA$B$<CR>

Missing parentheses

0010 PRI SQR(23~NOW IS THE TIMEjA$B$

0010 PRI SQR(23)~NOW IS THE TIMEjA$B$

Comma required

0010 PRI SQR(23)jNOW ~S THE TIMEjA$B$

0010 PRI SQR(23)jNOW_IS THE TIMEjA$B$

0010 PRI SQR(23);NQW IS THE TIME;A$B$

0010 PRI SQR(23) j!!OW IS THE TIMEjA$B$

0010 PRI SQR(23);NOW IS THE TIME;A$B$

0010 PRI SQR(23)j"B,OW IS THE TIMEjA$B$

0010 PRI SQR(23);"NOW IS THE TIMEiA$B$

0010 PRI SQR(23)j"NOW IS THE TIMEiA$B$

0010 PRI SQR(23)j"NOW IS THE TIME "iA$B $

Comma required

0010 PRI SQR(23)j"NOW IS THE TIME" jA$B$

0010 PRI SQR(23)j"NOW IS THE TIME" jA$ ;].$

10 PRINT SQR(23)j"NOW IS THE TIME"jA$jB$

Enter I

Enter )

Enter <CR>

Assumes NOW is variable name

Enter back space

Enter I

Enter "

Enter Fj

Enter I

Enter "

Enter <CR><CR>

Enter I

Enter

Enter <CR><CR>

Enter <CR>

3.4 Consistency in Listing

Because OASIS BASIC is an interpreter/compiler it saves statements in a compact, coded format. When a program listing is requested (or even a single line displayed) the coded format must be expanded to a display format. It does this expansion in a very consistent manner--consistency is desirable in programming:

All keywords and verbs are always spelled out fully.

All keywords and verbs are surrounded by spaces.

Multi-statement line separators are surrounded by spaces.

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CHAPTER. 3: BECOHIBG I'AHILIAR. VITH BASIC

Lists of variables, expressions, and line references are separated by their proper punctuation.

I/O channel specifications are surrounded by spaces.

Commas are added when the statement syntax requires.

Expressions are displayed without any embedded spaces.

The assignment operator is surrounded by spaces.

Any leading spaces in a line are maintained.

String literals are always surrounded with the double quotation mark character (").

For example, the following is performed (entry and display):

-AUTO <CR>

10 REM This is a remark<CR>

IF (A$ > B$) * 5/ (5+ VALUE%) THEN GO SUB 1000\STOP<CR>

A=23 * B<CR>

40<CR>

-LIST<CR>

10 REM This is a remark

IF (A$>B$)*5/(5+VALUE%) THEN GOSUB 1000 \ STOP

A = 23*B

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BASIC REFERENCE HABUAL

12 BASIC

CHAPTER. 4

PIlOGRAMMTRG IN BASIC

4.1 Structure of a BASIC Program

A BASIC program consists of a set of elements and syntax described in the numbers, labels, and statements are joined line containing instructions to BASIC. statements constructed with the language following chapters. Expressions, line to solve a particular problem, with each

4.1.1 Syntax

Syntax is a term refering to the structure of the parts of a statement and the punctuation characters separating those parts. As an example, the syntax of a sentence in the English language is: <subject> <verb> <object> <punctuation>.

Unfortunately for elementary school children (and university professors) the syntax of sentences has many acceptable variations with each variation having variations and options and exceptions.

On the other hand, computer languages are very structured with very specific syntax requirements for each statement (sentence). There may be options to the structure but there are ~

4.1.2 Character Set

Information OASIS BASIC uses the full ASCII (American Standard Code for

Interchange) character set for its alphabet. This set includes:

Letters A through Z

Letters a through z

Numbers 0 through 9

Special characters (see ASCII character set in appendix).

This character set enables you to include any ASCII character as part of a program.

BASIC translates the characters that you type into machine language; some characters are processed and some are left as entered.

The BASIC editor translates characters in the following manner:

Letters A through Z - left as entered.

Letters a through z left as entered if in a statement remark or string literal (enclosed in quotation marks); translated to upper case equivelent in all other contexts.

Non displayable characters (BELL, DCI, FS, etc) - ignored.

Other control characters -

BS treated as editing character (backspaces one position); is not entered into the actual line.

RT when entered after line number and before the start of the statement: translated to five (5) spaces; when entered in middle of statement translated into one space.

LF ignored.

VT ignored.

FF ignored.

CR treated as end-of-line character. In auto entry mode the next line number will be displayed.

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BASIC REFERENCE HABUAL

Special characters:

; When entered at start of statement is translated into REM.

Statement separator for multi-statement line.

4.1.3 Line Format

The general format of a program line is as follows: line number

1010 label

LABEL: verb

PRINT SQR operand

(X""2+Y'"2 )

All lines in a BASIC program must begin with a line number. This number must be a positive integer within the range of 1 through 9999. A BASIC line number is a label that distinguishes one line from another within a program and determines the placement of that line in the program.

Leading zeroes (as well as leading and trailing spaces) have no effect on the number. However, you cannot have embedded spaces within a line number.

4.2 Statements

BASIC statements consist of keywords that you use in ~onjunction with the elements of the language set: constants, variables, and operators. These statements divide into two major groups: executable statements and non-executable statements.

At least one space or tab must follow all statement keywords in order for BASIC to recognize the keyword as such. For example:

Acceptable

Unacceptable

10 PRINT CUR.DATE$

10 PRINTCUR.DATE$

Some keywords consist of two words such as PRINT USING, ON ERROR, MAT INPUT. These keywords must also be separated by at least one space or tab character. Two exceptions to this are the GO TO and GO SUB keywords. It is acceptable to use the keywords GOTO or GOSUB without a separating space.

Statement keywords are reserved, and therefore, cannot be used as a variable name

(see appendix "Reserved Keywords"). However, keywords can be used as line labels.

4.2.1 Single Statement, Multi-State.ent Lines

You have the option of typing either one statement on one line or several statements on one line.

A single statement line consists of:

A line number (from 1 to 9999).

An optional line label followed by a semicolon (:).

A statement keyword.

The body of the statement.

A line terminator.

This is an example of a single statement line:

10 PRINT A,BETA*TODAY+3.

14 BASIC

CHAPTER 4: PROGBAHHIliG IB BASIC

To enter more than one statement on a single line (multi-statement line), separate each complete statement separator. You must multi-statement line.

PRINT statements: with a backslant (). The backslant symbol is the statement type it after every statement except the last in a

For example, the following line contains three complete

10 PRINT ALPHA$;BETA; \ PRINT CUR.DATE$ \ PRINT "Total =";TOTAL

The line number labels the first statement in a line. Consequently, you must take this into consideration if you plan to transfer control to a particular statement within a program. For instance, in the previous example, you cannot execute just the statement

PRINT CUR.DATE$ without executing PRINT ALPHA$;BETA; and PRINT "Total =";TOTAL

All executable statements can appear in a multi-statement line.

The rules for structuring a multi-statement line are:

Only the first statement in a series has a line number.

Only the first statement in a series can have a line label.

Successive statements must be separated with a backslant.

4.3 Line Labels

All OASIS BASIC lines statements using the have line numbers and the line may be referenced by other line number of the line (GOSUB, GOTO, etc.). Lines may also have a line label.

Line labels are useful for referencing lines when the line number is unknown, when you wish to "document" the function of a line or sequence of lines, etc.

A line label consists of one or more letters, digits, or periods with the first character being a letter. There is no limit on the length of a line label but you should use labels that are short, but still meaningful (you have to type the entire label each time it is referenced).

A line label must be unique within a program. When a line label is defined it must precede any statements on the line and be separated from the first statement by the colon character (:).

The following lines are all acceptable uses of line labels:

10 MAINLINE: WHILE CONTROL

20 GOSUB INPUT.ROUTINE

= 0

30 IF INPUT$ = "" GOTO ERRORS

40 INPUT.ROUTINE: REM Subroutine to accept input

It is permissible for a line label to be a keyword (no confusion arises due to the context in which a line label appears), however a label may not start with the letters REM.

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BASIC REl'ER.ERCE IWWAL

4.4 Documenting Procedures

BASIC allows you to document your methods, insert notes and comments, or leave yourself messages in the source program. This type of documentation is known as a remark or comment. There is only one way of inserting comments within a BASIC source program: the REM statement.

BASIC ignores anything in a line following the keyword REM including a backslant character. The only character that ends a REM statement is a line terminator.

Therefore, a REM statement must be the only statement on a line or the last statement in a multi-statement line.

10 LET A=B REM Variable A receives current value of B

You can use the semicolon character (;) instead of the keyword REM. BASIC will translate this into the keyword REM and display it as such whenever a listing is produced.

You can use the line number of a REM statement in a reference from another statement, i.e. GOSUB.

Another method of documentation, used in conjunction with remarks, is indentation.

Any spaces or tabs entered between the line number and the first character of the line will be maintained by BASIC for listing purposes. This allows you to show the structure or hierarchy of the program.

Remarks and/or leading spaces have no impact on a program after it is compiled (one of the functions of compilation is to remove these from the program).

Refer to the appendix documentation techniques. containing

4.5 Entering and Modifying Programs program examples for illustrations of

OASIS BASIC allows programs to be entered, debugged, and modified while in the

BASIC environment. Refer to the chapter on "BASIC Commands" for information on the use of the commands in editing a program (AUTO, CHANGE, DELETE, DISPLAY, DOWN,

LIST, LOCATE, MODIFY, and UP).

It is important to note that BASIC performs syntax analysis when the statement is entered, not when the statement is executed. This not only increases the speed of execution but also prevents any syntax errors from being entered. The main advantage of this pre-execution syntax analysis is that the program is free of all syntax errors even though some of the lines in the program have never been executed.

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CHAPTER 5

KI.DtENTS OF THE BASIC LANGUAGE

In order to write programs in BASIC you must be familiar with the terms and phrases used to describe the program elements. You will probably recognize most of these terms from previous experience; however, the following sections define these terms within the context of OASIS BASIC.

5.1 Constants

A constant is an element whose value does not and cannot be changed during the execution of a program.

There are three types of constants in BASIC:

Numeric (also called floating point numbers)

Integer (whole numbers)

String (alphanumeric and/or special characters)

5.1.1 Numeric Constants

A numeric constant is one or more decimal digits, either positive or negative, with a decimal point specified. (The decimal point may be omitted when the constant is a whole number outside of the range +32767 to -32767.)

The following are all valid numeric constants:

25.

-1234.01

12345678901.23

3.14159

.000002

-9876543210123

234567

32760.

.1234567890123

Numeric constants cannot contain any embedded space characters.

BASIC accepts and maintains numeric constants within a range of 13 significant digits.

When you type a numeric constant with more than 13 significant digits specified the excess, least significant digits will be truncated.

It is possible to enter and maintain a number that is outside the range of precision by using an alternate format:

<+ or ->x.xxxxxxxxxxxxE<+ or ->nnn

Where:

<+ or -> is the sign of the number. The plus sign is optional with positive numbers; the minus sign is required with negative numbers. x is the number with up to 13 significant digits.

E nnn represents the words "times 10 to the power of" is the exponential value (the power of 10) in the range of +126 to -126

This method of mathematical shorthand is called E format, floating point notation, or scientific notation. It is BASIC's way of representing scientific notation. To

BASIC - 17 -

BASIC REl'ERENCE HAlflJAL use this format, append the letter E to the number, follow the E with an optionally signed integer constant. This constant is the exponent--it can be 0 but never blank.

The following are all valid numeric constants, E format:

1.2568E10

-1.234567890123E-126

All E notation numeric constants are normalized after entry, that is, the decimal point (and the nnn value) is adjusted to be after the first significant digit. For example, entry of the constant 12345.58E10 will be normalized to be 1.234558E+014.

If a number entered in E notation can be expressed in normal notation, it will be.

For example, entry of the constant 1.25E6 will be printed as 1250000.

5.1.2 Integer Constants

8.254681325257E-120

2358.256824798E2

1235E-30

1.2E60

An integer constant is a special type of numeric constant that is a whole number

(no fractional part) written without a decimal point and in the range of +32767 to

-32767. For example, the following numbers are all integer constants:

32767 o

-15

-32767

-1234

100

10000

Integers, though normally entered in decimal format (base 10) may be entered in hexadecimal format (base 16). When this is done the integer constant must be terminated with the letter H. Hexadecimal values may use the digits 0 through 9 and the letters A through F. A hexadecimal constant must start with a digit (use a zero if necessary).

The following are all acceptable hexadecimal integer constants:

1234H

OFFFFH

OABH

-1234H

245H

OFH

The following are all unacceptable integer constants:

12AB

OFFFGH

123456

1.24

12E10

Invalid decimal or missing uH u

G is not valid hexadecimal character

Outside of range of integer

Not an integer

Outside of the range of an integer

5.1.3 String Constants

A string constant (also called a string literal) is one or more alphanumeric and/or special characters, enclosed in a pair of double quotation marks (U) or single quotation marks ('). Include both the starting and ending delimiters when typing a string constant in a program. These delimiters must be of the same type (both double quotation marks or both single quotation marks).

Each character in a string constant can be a letter, a number, a space, or any

ASCII character except a line terminator. The value of the string constant is determined by all of its characters. BASIC maintains every character between the delimiters exactly as you entered it into the source program.

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CHAPTER. 5: ET.F.HKRTS 01' THE BASIC LAHGUAGE

BASIC does not normally print the delimiting quotation marks when a string constant is printed on the console, printer, or file.

Quotation marks may be included as part of the text of a string constant by either: using the opposite type of delimiting quotation marks (i.e. single within double, double within single); or by doubling the embedded quotation mark ('"' or ").

The following are all acceptable string constants:

String constant Internal representation

"This is a string constant"

'This is also a string constant'

"Look at Spot's spots."

'Look at Spot"s spots.'

"He said, ""Open the book."""

This is a string constant

This is also a string constant

Look at Spot's spots.

He said, "Open the book."

5.2 Var1.ables

Variables differ from constants in that their values may change during the execution of the program. For this reason variables are refered to by their name, not their current value. BASIC uses the most recently assigned value of a variable when performing calculations. This value remains the same until a statement is encountered that assigns a new value to that specific variable.

BASIC allows three types of variables:

Numeric variables (name terminated with letter, digit, or period)

Integer variables (name terminated with %)

String variables (name terminated with $)

The type of a variable is determined by the name of the variable. BASIC allows variable names to be of unlimited length (a reasonable maximum is about two hundred characters due to the line length restriction of 255 charactes).

Variable names for the three types of variables have a common syntax:

First character must be a letter (A Z)

Subsequent characters are optional and may consist of letters (A - Z), digits (0 - 9) or the period character (.).

The space character cannot be used as part of a variable name.

The variable name cannot be a reserved word.

The following are all acceptable variable names:

TOTAL

SUB.TOTAL

SUB.TOTALI

SUM

SUMI

CUST.NAME$

INDEX%

INTEREST

PRIME. INTEREST

P.INT

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BASIC REFERENCE HARUAL

The following are all unacceptable variable names:

I23A

A$ONE

SQR

Must start with letter

Only special character allowed is period

Reserved word

A variable name is identified as one of the three types of variables by a terminating type character. This type character is part of the name and makes the name different from a variable name with a different type character. For example, the following three variable names each refer to a different variable:

CUSTOMER

CUSTOMER%

CUSTOMER$

(numeric variable)

(integer variable)

(string variable)

5.2.1 Numeric Variables

A numeric variable is a named location in which a single numeric value is stored.

Numeric variables contain numeric (floating point) values. A numeric variable is identified by a variable name (discussed above) without a terminating type character (last character is a letter or digit).

The following are all acceptable numeric variable names:

COUNT

MAXIMUM

INDEX

MINIMUM

RECORD.NUMBER

TOTAL

The following are all unacceptable numeric variable names:

9TOTAL

TOTAL.

RECORD*COUNT

TWO/3

When a numeric variable is first defined its value is set to zero (0). Execution of the RUN instruction clears all variables. If you require an initial value other than zero you must assign it with the LET statement.

Note: Because other BASIC languages may not set all variables to zero before program execution you should not rely on this feature. Good programming practice dictates that you initialize all variables at the beginning of the program.

5.2.2 Integer Variables

An integer variable, similar to a numeric variable, is a named location in which a single integer value is stored. Integer variables contain integers (whole, non-fractional values). An integer variable is identified by a variable name

(discussed above) with a terminating type character of a percent (%) symbol.

The following are all acceptable integer variable names:

RECORD%

Al%

RECORD.NUMBER%

INDEX%

CODE%

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CHAPTER. 5: EI·DlENTS OF mE BASIC LAlIGUAGE

The following are all unacceptable integer variable names:

TOTAL 1 $

NAME$ONE

1 TOTAL %

REC.INDEX

When an integer variable is first defined its value is set to zero (0). Execution of the RUN instruction clears all variables. If you require an initial value other than zero you can assign it with the LET statement.

An integer variable always contains an integer value (see integer constants for restrictions). If a numeric constant or variable is assigned to an integer variable, BASIC first truncates the fractional part of the floating point number.

If the resulting whole number is outside the range of an integer (+32767 to -32767) the number is set to 32767 with the proper sign and an error occurs (refer to the

ON ERROR GOTO statement and the appendix on error codes).

When you assign an integer variable or constant to a numeric variable BASIC will print the numeric value as an integer but maintains it as a floating point number internally.

5.2.3 String Variables

A string variable is a named location in which a single alphanumeric string of characters is stored. A string variable is identified by a variable name

(discussed above) with a terminating type character of the dollar sign ($).

The following are all acceptable string variable names:

CUST.NAME$

CUST.CITY.STATE.ZIP$

B5$

CITY$

DEBIT.CREDIT$

NAME $

DESC$

The following are all unacceptable string variable names:

CUST-NAME$

$ NAME

COUNT%

Strings have a value and a length. BASIC initializes all string variables to a length of zero--referred to as a null string--when a string variable is first referenced. During the execution of a program the length of a character string associated with a string variable can vary from zero to a limit of 255.

5.3 Array Variables

An array is a list or table of numeric, integer, or string variables with one or two subscripts. The subscript is a pointer to a specific location in a list or table in which a value is stored. You designate the pointer with either one or two subscripts enclosed by parentheses. When there are two subscripts they are separated by a comma. The value stored may be a numeric, integer, or string value, depending upon the array type.

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To name an array start with a numeric, integer, or string variable name:

ITEMS ITEMS % ITEMS $

Then add the subscript reference:

ITEMS (4) ITEMS%(2,10) ITEMS $ (15)

ITEMS(4) refers to the fifth value in the array ITEMS. It is the because the first value has a subscript of zero (a number base of 0). changed by the OPTION statement. fifth value

This may be

ITEMS%(2,10) refers to the value "indexed" by row two, column ten in the table

ITEMS%.

As mentioned, an array may have one or two subscripts. The number of subscripts is refered to as the number of dimensions of the array (see DIM statement). An array defined with one dimension must always be referenced with only one subscript.

Likewise, an array defined with two dimensions must always be referenced with two subscripts.

Array names must be unique from variable names (the subscript references are not actually part of the name). This means that after the array ITEMS has been defined all references to a variable ITEMS are unacceptable because the name ITEMS is an array and must have subscripts. (The MAT statements are an exception to this because they only operate on arrays.) An attempt to use a variable name as an array and a non-array will result in an "Inconsistent usage" error.

Arrays are defined either explicitly with the DIM statement, or implicitly by using the array name in an assignment statement (LET) or as a term in an expression.

When an array is defined implicitly it is automatically dimensioned with an upper subscript of ten with one or two dimensions, depending upon the number of supscripts in the array reference. For example:

LET ITEMS(4) = 1234 will dimension the array ITEMS to have eleven elements with subscripts: 0, 1, 2, 3,

4, 5, 6, 7, 8, 9, and 10.

LET ITEMS%(2,7)

23 will dimension the array ITEMS% to have two dimensions with maximum subscripts of

10 in each dimension. This equates to 121 elements (OPTION BASE 0) or 100 elements

(OPTION BASE 1).

If it is desired to have either fewer or more elements in an array you must use the

DIM statement.

References to an array with a subscript greater than the size that the array was defined as will cause an error to occur (see ON ERROR GOTO statement and the appendix on error message's).

Most people find it inconvenient to work with a subscript number base of zero. For that reason the OPTION BASE 1 statement is provided. Refer to the OPTION statement for details on its use.

- 22 BASIC

CHAPTER. 5: ELEMENTS OF THE BASIC LANGUAGE

Note: It is always a good practice to use the DIM statement to define the size of an array to avoid wasting storage space and to document the arrays and dimensions in use.

Array Example

As an example let the array ITEMS% be dimensioned to a size of 4 rows by 8 columns.

To accomplish this you would use the statement: DIM ITEMS%(3,7) and the layout of the array would be:

R o

° w 2

S 3

COL U M N S

1 2 3 4 5 6 7 °

(0,0)

(0,1)

(0,2)

(0,3)

(0,4)

(0,5)

(0,6)

(0,7)

1-------1-------1-------1-------1-------1-------1-------1-------1

(1,0)

(1,1)

(1,2)

(1,3)

(1,4)

(1,5)

(1,6)

(1,7)

1-------1-------1-------1-------1-------1-------1-------1-------1

(2,0)

(2,1)

(2,2)

(2,3)

(2,4)

(2,5)

(2,6)

(2,7)

1-------1-------1-------1-------1-------1-------1-------1-------1

(3,0)

(3,1)

(3,2)

(3,3)

(3,4)

(3,5)

(3,6)

(3,7)

5.4 Functions

A function, in BASIC, is a special type of variable or constant. predefined (or user defined) series of numeric and/or string operations.

It is a

A function name looks very much like an array name except that instead of one or two subscripts the function has zero or more "arguments". The arguments of a function are values that the function operates on or returns to the statement referencing it.

There are three types of functions:

Intrinsic functions

User defined functions

USR functions

A function is used just like a variable or constant with one exception: a function cannot be assigned a value.

The following are all acceptable function names:

SQR(25)

INT(TOTAL)

FNA$(A1$,B2)

USR(3,A$)

5.4.1 Intrinsic Functions

Intrinsic - return square root of 25

Intrinsic - return integer value of TOTAL

User defined function

USR subroutine function

Intrinsic functions are functions that are an integral part of BASIC and need not be defined by the programmer.

The intrinsic functions provided with OASIS BASIC include functions to perform trigonometric operations, algebraic operations, general string operations, general

BASIC REl'ERERCE IWlUAL numeric operations, logical operations, and screen control operations.

For a detailed description of the intrinsic functions refer to the chapter

"Functions" later in this manual.

Intrinsic function names are all reserved words and as such, cannot be used as variable names. (See appendix on "Reserved Words".)

5.4.2 User Defined Functions

A user defined functions is one that must be defined by the programmer in each program.

A user defined function name always starts with the letters FN.

For a description of how to write a user defined function refer to the DEF statement.

When a reference is defined with a DEF reference. This may subs crip ts • made to a user defined function name and that function is not statement the reference will be interpreted as an array cause an error when the function arguments are analyzed as

5.4.3 usa

Functions

A USR function is a call to a user written, assembly language, subroutine.

There can only be one USR function available at anyone time, although it may have several "entry points".

Refer to the

OASIS MACRO function.

OPTION USR statement for details on the USR function.

Assembler Language Reference Manual for details on

Refer to the writing a USR

5.5 Expressions

Expressions are used extensively throughout this manual and within BASIC itself.

Basically an expression is the specification of a series of operations to be performed on variables, constants, and functions, resulting in one value.

The use of an expression in BASIC is similar to expressions you use in your everyday work. For example, the term "work week" is used in estimating the time it takes to do a particular job. To determine the meaning of the term ''work week" you normally multiply the number of hours a person works in a day by the number of days he works in a calendar week (normally 8 hours by 5 days). That is an example of an expression. Of course, in BASIC, you don't exactly use the same wording but it is quite similar:

LET WORK. WEEK = HOURS

DAYS

In BASIC there are several types of expressions:

Arithmetic expressions

String expressions

Logical expressions

Relational expressions

- 24 BASIC

CHAPTER. 5: ELEHKNTS OF THE BASIC LANGUAGE

The type of an expression is determined by the type of operations it performs and the type of the constants, variables, or functions that it performs the operations on.

An expression can be as simple as a single constant or as complex as several hundred terms and operators.

The following are examples of expressions in BASIC:

2.345

A*SQR(GIRTH%)

NAME$&"abcdefg"

"Name: "&SPACE$(4)&NAME$

A OR B

NOT TRUE%

NAME1$ > NAME2$

CAT <= (BIRD AND DOG)

Arithmetic expression

String expression

Logical expression

Relational expression

Relational expression with logical subexpression

An expression is composed of terms (constants, variables, and/or functions) and operators (+, *, &, etc.). Operators are either binary operators (operate on two terms) or unary (operate on one term). An example of a binary operator is the multiplication operator (*). An example of a unary operator is the negative operator (-). Some operators can be either binary or unary such as the plus operator (+).

Expressions are frequently used in BASIC assignment statements (LET) but there are many other uses for expressions. The syntax of each of the statement descriptions specifies where an expression can be used and what type of expression is allowed.

Although there are four distinct types of expressions many expressions used in a

BASIC program are generally a combination of two or more types of expressions.

5.5.1 Arithmetic Expressions

The arithmetic expression is the most common type of expression. An arithmetic expression has an arithmetic value (integer or floating point) and is defined as:

<arithmetic term> [<arithmetic operator> <arithmetic term>]

Arithmetic term

An arithmetic term may consist of any of the following:

Numeric constant

Integer constant

Numeric variable or array

Integer variable or array

Numeric function

Integer function

Logical expression

Relational expression

Arithmetic expression

BASIC - 25 -

BASIC REl'ERERCE HANUAL

Arithmetic operators

Operator

Function

Exponentiation

Multiplication

Division

Addition (or unary positive)

Subtraction (or unary negative)

English raised to the power times divided by plus minus

An arithmetic expression whose terms are mixed in type (both integer and floating point) yields a floating point value. ,An arithmetic expression whose terms are the same type (all integer or all floating point) yields a value of the same type.

You cannot place two arithmetic operators together unless the second operator is a unary minus or unary plus.

The following are examples of valid arithmetic expressions:

A%+23

SUB.TOTAL+CURRENT*UNIT.PRICE

ONE%*THREE

+1/-4

PI*RADIUS+2

3*4/(PI*R2)

Integer result

Numeric result

Note that the last example uses parentheses. Parentheses may be used anytime to clarify' the sequence of operations or to change the sequence (see section on

, "Evaluating Expressions" below).

5.5.2 String Expressions

A string expression has a string value and operates only on string terms.

String terlll

A string term may consist of any of the following:

String constant

String variable or array

String function

String expression

String operator

A string operator may consist of:

Operator

[n:m]

Function

Concatenation

Substring

English is concatenated with from character n through m (unary operator)

- 26 BASIC

CHAPTER. 5: ET.EHRNTS OF THE BASIC LANGUAGE

The concatenation operator allows two strings to be joined

"ABCDEF"&"GHIJKLMN" produces ABCDEFGHIJKLMN. The concatenation operates on two terms (binary operator). together. Thus operator always

The substring operator extracts characters from a string. The n in the operator represents the starting character position; the m in the operator represents the ending character position. The result of a substring operation is always a string of length m-n+l, even when one or both of nand m are greater than the current length of the string being operated on. The m value must be greater than or equal to the n value. The substring operator is a unary operator that operates on the preceding term, rather than the following term like other unary operators. The substring operator may be followed by the concatenation operator.

The following are examples of string expressions: (assume all string variables contain the constant "ABCDEFGH")

Result Expression

NAME $

"John Doe"

A$&"Message"

CITY$&", "&ST$&" "&STR$(ZIP%)

A$ [2: 4]

''''&ALPHA$ [4:9] &ALPHA$ [11: 12]&''''

(A$&B$[5:9]) [3:10]

ABCDEFGH

John Doe

ABCDEFGHMessage

ABCDEFGH, ABCDEFGH 12345

BCD

"DEFGH

CDEFGHEF

Note that in the last example parentheses were used. Parentheses are discussed in the section "Evaluating Expressions" below. In this example the parentheses are used to produce a "sub-expression" for the second substring operator.

The following are invalid string expressions:

A$/"ABCD"

A$ [4: 1]

A$>B$

A$&123

A$[2:3]&

Cannot include arithmetic operator

Invalid substring reference

Relational expression (see below)

Cannot include arithmetic term

Concatenation requires two terms

5.5.3 Logical Expressions

A logical expression operates on integer values and produces an integer value. A logical expression is defined as:

<arithmetic term> <logical operator> <arithmetic term>

Arithmetic term was defined above in the section "Arithmetic Expressions".

BASIC 27 -

BASIC IlD'EIlERCE IlARUAL

Logical operators

A logical operator is any of the following:

Operator

NOT

AND

XOR

IMP

EQV

Function

Invert bit in one term (unary)

Bit on in both terms

Bit on in either term

Bit on in only one term

Bit on in second term only if on in first term

Bit either on in both terms or off in both terms

Logical expressions are comparisons between the corresponding Ubits" terms of the expression. A bit is a binary (either on or off) information. An integer value is composed of sixteen bits. A decimal expressed in bits by converting the number to base two notation and of the two piece of integer is adding any leading binary zeros, if necessary. The following is a list of some values in decimal and binary: equivalent

Decimal

100

32767

-32767

-1 o

Binary bits

00000000 00000000

00000000 00000001

00000000 00000101

00000000 00010111

00000000 01100100

01111111 11111111

10000000 00000000

11111111 11111111

Note that a decimal zero has all zero bits and a decimal bits. This relationship between decimal and binary is relational expressions, discussed in the following section. minus one has all one used in the result of

The terms of a logical point in value BASIC performed. expression must be integers. When will integerize them before the the terms are floating logical operation is

Logical expressions are valid wherever arithmetic expressions are allowed in BASIC, however, both terms must be integers (floating point terms will automatically be ufixed U) •

The following tables are called truth tables. They show graphically the results of the logical operations for every possible combination of two bits.

- 28 BASIC

NOT

CHAPTER. s:

EI.DfKN'rS 01' TIlE BASIC LABGUAGE

Logica1 Truth Tab1es

NOT A%

A% B%

A% OR B%

A% B%

1 1

.ABD

A% AND B%

A% B%

1 1

XOB.

A% XOR B%

A% B% o

0 o

IHP

A% IMP B%

1 o

EQV

A% EQV B%

The following are examples of valid logical expressions:

NUMl% OR NUM2%

I% AND 23

I% AND (NUMBER XOR TOTAL) IMP TEST%

(A AND B) OR (A AND C)

STRING$ >= "A" AND STRING$ <= "z"

Note that in the next to the last example parentheses were used. discussed in the section "Evaluating Expressions" below. In parentheses are used to specify the sequence of evaluation.

Parentheses are this example the

The following are all unacceptable logical expressions:

STRING$ OR "HELP"

NUMl% AND OR NUM2

Must be arithmetic terms

Binary operators cannot be adjacent

Logical expressions are normally used to evaluate terms that are the result of relational expressions (bits all on or all off); however, since the logical expression does compare all sixteen bits of each of the terms there are many other uses for logical expressions. One of the more common of these other uses is binary coded information or "bit swtiches".

BASIC - 29 -

BASIC REFERENCE HABUAL

Some examples will illustrate how the logical operators work on non-relational values:

15 AND 14 . 0000000000001111 (15)

AND 0000000000001110 (14)

----~-----------

0000000000001110 (14) (True)

10 OR 23

NOT 153

0000000000001010 (10)

OR 0000000000010111 (23)

----------------

0000000000011111 (31) (True)

NOT 0000000010011001 (153)

----------------

1111111101100110 (-154) (True)

25 XOR 13 0000000000011001 (25)

XOR 0000000000001101 (13)

----------------

0000000000010100 (20) (True)

29 XOR 29

234 EQV 3429

56 IMP 720 0000000000111000 (56)

IMP 0000001011010000 (720)

----------------

1111111111010111 (-41) (True)

As you can see there doesn't appear to be a relationship between the decimal terms and the decimal result of the expression; however, using the binary representations of the integers (as BASIC does) there is a definite, Boolean, relationship. This can be utilized to make an integer value contain sixteen, binary (on/off) switches.

When using binary switches the logical expressions can be utilized to set or mask the number to expose the bit switch desired.

5.5.4 Relational Expressions

0000000000011101 (29)

XOR 0000000000011101 (29)

----------------

0000000000000000 (0) (False)

0000000011101010 (234)

EQV 0000110101100101 (3429)

----------------

1111001001110000 (-3472) (True)

A relational expression operates on numeric or string terms and produces a sixteen

(16) bit integer value of -1. (true all bits on) or 0 (false - all bits off). A relational expression is defined as:

<arithmetic term> <relational operator> <arithmetic tera> or

- 30 BASIC

CIIAPTEIl 5: E1.DfENTS OF THE BASIC LABGUAGE

Arithmetic and string terms were defined above under the sections "Arithmetic

Expressions" and "String Expressions" respectively.

Relational operators

A relational operator is any of the following:

Function Operator

'<=

Greater than

Greater than or equal to

Less than

Less than or equal to

Equal to

Greater than or less than (unequal to)

The following are all acceptable relational expressions:

STRING$

NUMI

> "HELLO"

<= NUM2

NUMBER% <> 225*(5-0NE)

539 = ONE

String relation

Numeric relation

Numeric relation with arithmetic sub-expression

Numeric relation (not assigment)

The following are all unacceptable relational expressions:

"Goodbye" <> 25

NUMI II

NUM2

5.5.5 Expression Evaluation

Can't mix string with numerics

Invalid operator

BASIC evaluates expressions according to operator precedence. Each arithmetic, string, logical, and relational operator joining an expression has a predetermined position in the hierarchy of operators. The operator's position tells BASIC when to evaluate the operator in relation to the other operators in the same expression.

Parentheses may be used to change the sequence of evaluation of an expression.

Nested parentheses (one set of parentheses within another) may be used to cause the innermost subexpression to be evaluated first.

Parentheses may also be used as a documentation aid to clarify a complex expression.

The following table lists all of the expression operators in the hierarchy of evaluation.

BASIC - 31 -

BASIC BD'EIlERCE IWWAL

Operator Precedence

Operator

()

(exponentiation) functions substringing

+ (unary)

- (unary)

(multiplication)

/ (division)

+ (addition)

NOT

AND

XOR

EQV

IMP

- (subtraction)

& (concatenation)

> (greater than)

>= (greater or equal)

< (less than)

<= (less then or equal)

= (equal)

<> (unequal)

I Hierarchy

Notice that some operators have the same hierarchy number. This means that they are equivelent in precedence and will be evaluated in a left to right manner. This also applies to an expression with more than one occurence of the same operator.

As an example, consider the following expression:

152+122-35*8

BASIC evaluates this expression in five, ordered steps:

1. 152 = 225

5. 369-280 = 89

Result is 89

Exponentiation (left most)

2. 122

3. 35*8

= 144

= 280

4. 225+144

Exponentiation (next)

Multiplication

= 369 Addition

Subtraction

Arithmetic expressions with mixed arithmetic types (floating point and integer) will "float" all of the terms before expression evaluation.

As mentioned, parentheses can alter the sequence of evaluation (and possibly, the result). Consider the following, similar expressions and evaluations:

- 32 BASIC

252+302/2

1. 252 = 625

2. 302 = 900

3. 900/2 = 450

4. 625+450 = 1075

Result is 1075

CBAPTKR. 5: ELEHENTS OF THE BASIC LANGUAGE

(252+302)/2

1. 252 = 625

2. 302 = 900

3. 625+900

4. 1525/2

1525

= 762.5

Result is 762.5

Note that in the above precedence table the relational operators have precedence over the logical operators.

Consider the following expression and evaluation:

"A">"B" OR "A"<="D"

1. "A">"B" = 0

2. "A"<="D" = -1

3. 0 OR -1 = -1

0000000000000000 (false)

1111111111111111 (true)

BASIC - 33 -

BASIC REFERENCE MARUAL

- 34 BASIC

CBAPTEIl 6

FORHATED OUTPUT

Sometimes the format of output is as important as the content. BASIC provides a means of controlling this format with the PRINT USING statement and the FORMAT$ function. Both the statement and the function allow you to control the appearance of data, thus enabling you to create formatted list, tables, reports, and forms.

The following example programs print a series of numbers. One program uses the

PRINT statement and the other uses the PRINT USING statement.

0010 PRINT 1

0020 PRINT 10

0030 PRINT 123.5

0040 PRINT 100

0050 PRINT .23433

0060 PRINT 1000000

0070 PRINT -3

0005 MASK$ = "11,11111111111111.1111-"

0010 PRINT USING MASK$,l

0020 PRINT USING MASK$,10

0030 PRINT USING MASK$,123.5

0040 PRINT USING MASK$,100

0050 PRINT USING MASK$,.23433

0060 PRINT USING MASK$,1000000

0070 PRINT USING MASK$,-3

-RUN

123.5

100

0.23433

1000000

-3

-RUN

1.00

10.00

123.50

100.00

0.23

1,000,000.00

3.00-

As can be seen the PRINT statement left justifies numbers, performs no rounding, and indicates negative values with a leading, floating, minus sign; PRINT USING

(and the FORMAT$ function) allows you to format numbers in several ways, making it easier to read and intepret the output.

There are several number formatting functions that the PRINT USING statement and the FORMAT$ function allows you to specify:

Number of significant digits.

Location of decimal point.

Exponential format.

Inclusion of special symbols (asterisk fill, dollar sign, commas, leading zeros) •

Alternate methods of indicating negative values (trailing sign, < >, trailing DB or CR).

There are also several string formatting functions that the PRINT USING statement allows you to specify:

Number of characters.

Left justified format.

Right justified format.

Center justified format.

Extended format.

All of the formatting functions for the PRINT USING statement and FORMAT$ function are specified by using a mask that contains the formatting information. For details on the general syntax of the PRINT USING statement and FORMAT$ function

BASIC - 35 -

BASIC REDB.ERCE MARUM. refer to their respective sections.

PRIRT US DIG and FORMAT Masks

PRINT USING and FORMAT$ masks are string expressions that contain formatting and non-formatting characters that control the format of the field output.

A PRINT USING mask may contain the format information for more than one field; a

FORMAT$ mask contains the format informattion for only one, numeric field.

Non-formatting characters include any, and all, characters not specified here as formatting characters and act as literal information and field separators. These non-formatting characters will be included in the output field. Formating characters that operate in pairs (\\ $$ ** DB CR ~~ ~~~ ~~~~ ~~~~~) will act as non-formatting characters if they appear separately ($ * D B C R ~). Additionally, the formatting characters comma, period, minus, DB, CR, +, and > act as non-formatting characters if they appear separate from a numeric field specification.

For example:

0010 PRINT USING "Example 1: 1111",1

0020 PRINT USING "This is a DB record 99",1

-RUN

Example 1: 1

This is a DB record 01

6.1 Humeric Field Masks

Numeric field masks may be used for both the PRINT USING statement and the FORMAT$ function. A numeric field mask requires a numeric value as input. When an attempt is made to use a numeric field mask with a string field the error "Invalid using" will occur.

The output of a numeric field specification mask will always be the same length as the length of the specification mask (unless there is insufficient space--see

"Field Specification too Small"). If necessary, the number to be output is rounded by truncating digits to the right of the decimal point not specified in the mask or rounding the last digit specified to the right of the decimal point if the next digit was five or greater. When a number must be rounded to make it fit in the specified mask rounding·will be performed on the absolute value of the number. For example:

0010 PRINT USING "//11",1.4,1.5,1.6

RUN

0010 PRINT USING "/11/",-1.4,-1.5,-1.6

RUN

-1

-2

6.1.1 Specifying Humber of Digits

All of the numeric, formatting characters are used to specify the total length of the output field; however, only the #, 9, comma, **, and $$ are used to specify the number of digits to be included. Conventionally, the used to specify the number of digits.

# and/or 9 characters are

- 36 BASIC

CIIAPTER. 6: FOBHATED OUTPUT

The 9 character reserves space for one digit and, if it appears before the decimal point specification, indicates that leading zeros are not to be suppressed. The 9 character cannot be used to format negative values.

The # character reserves space for one digit and indicates that leading zeros are to be suppressed.

The # and 9 characters may be mixed; however, if one or more 9 characters appear before the decimal point specification, leading zeros will not be suppressed.

When no sign specification is used and a negative value is output, a leading, floating, minus sign will be output, using one of the digit positions (as stated earlier, the output field will always be the same length as the mask field).

For example:

0010

0020

0030

0040

0050

0060

-RUN

PRINT USING" "",I

PRINT USING"

PRINT USING

111''',1

"/11111111''',1

PRINT USING "91111111''',1

PRINT USING "/11111111'''-1

PRINT FORMAT $ (23," 11111111")

00001

-1

Decimal Point Specification

0010 PRINT USING " 9",1

0020 PRINT USING " 99",1

0030 PRINT USING "99999",1

0040 PRINT USING "#91/9#",1

0050 PRINT USING "99999-",-1

0060 PRINT FORMAT $ (23, "91111111/ ff

)

00001

00001-

00023

You can specify the number of digits to the left and right of the decimal point by using a period embedded in the number field specification. The number of digits to the right of the decimal point specification will always be printed, even if zeros are required to do so.

If one or more digits are specified to the left of the decimal point there will always be at least one digit output, even if a zero is required to do so, unless there is only one place specified, the number is negative and less than one, and there is no sign specification used, in which case the negative sign will be output immediately before the decimal point.

Specifying fewer places to the right of the decimal point than the number actually contains will cause rounding to occur to allow the number to fit. Specifying fewer places to the left will cause an error (see Specification too Small).

Only one decimal point may be specified in a numeric field mask. second decimal point will indicate the end of the mask field and another numeric field.

Specifying a the start of

BASIC 37 -

BASIC REFERENCE HANUAL

For example:

0010 PRINT USING "

0020 PRINT USING"

.1111",0

11.1111",1

0030 PRINT USING"

0040 PRINT USING

1111.1111",1.2345

"1111111111.11111111",1.24

-RUN

.00

1.00

1.23

1.2400

6.1.3 Comma Specification

0010 PRINT USING" .99",0

0020 PRINT USING" 9.99",1

0030 PRINT USING "99.99-",-.2

0040 PRINT USING" 9.999",-.234569

-RUN

.00

1.00

00.20-

%-.234569

Commas may be inserted in the output field by using the comma character anywhere in the field, to the left of the decimal point specification, if used.

When the comma character is used the output field will be formatted with a comma appearing every third digit from the decimal point (or least significant digit if the decimal point specification is not used), working from right to left.

The comma character is also a digit specifier.

More than one comma may be specified for easier reading of the format mask:

11,111111111111111111 has the same effect as 111111,111111,111111 although the second form is more graphic in its meaning.

For example:

0010 PRINT USING

0020 PRINT USING

0030 PRINT USING

-RUN

1,000,000,000

1,234.56

"11,11111111",1

"11,1111111111111111111111", 1E ..... 9

"1111,111111111111.1111",1234.56

0010 PRINT USING

0020 PRINT USING

0030 PRINT USING

-RUN

12,345

1,000,000,000

1,234.56

"1111,111111",12345

"11,111111,111111,111111", 1E ..... 9

"11,/11/11,111111.1111,"1234.56

6.1.4 Dollar Field Specification

A number may be formatted with a dollar sign immediately before the most significant digit by using the floating dollar sign specification of two dollar sign characters together. (To format a number with a dollar sign before the field use a single dollar sign character and it will be treated as a non-formatting character. )

The double dollar sign fill specification, specification) • characters must be at the start of the field (the asterisk if used, must be before the floating dollar sign

The double dollar sign characters indicate that a floating dollar sign is to be generated and one position is to be reserved for a digit.

If the number to be formatted is negative you must use the sign specification, otherwise a using error will occur.

The numeric field specification character 9 may not be used in a field with

- 38BASIC

CHAPTER 6: !'OIDIA.DD OUTPUT floating dollar sign specification. When it is it will be interpreted as the end of the field and the start of the next numeric field.

Extra dollar sign characters may be used instead of the

$$$$$$$$ is the same as $$######. n character. For instance,

For example:

0010 PRINT USING "$$111111.#11",12

0020 PRINT USING "$$111111.1111",1234

0030

-RUN

PRINT USING

$12.00

$1234.00

$1234.00-

"$$111111.1111-", -1234

0010 PRINT USING" $$",1

0020 PRINT USING "$$,1111111111.1111",12345

0030 PRINT USING "$$111111111111.1111-", -12345

-RUN

$12,345.00

$12,345.00-

6.1.5 Asterisk Fill Specification

A number may be formatted with leading asterisk instead of leading zeros by using the asterisk fill specification of two asterisk characters.

The asterisk fill specification, if used, must appear at the very start of a numeric field specification.

The double asterisk characters indicate that any leading zeros are to be replaced with asterisks and that two positions are to be reserved for digits.

If the number to be formatted is negative you must use the sign specification, otherwise a using error will occur.

The numeric field specification character 9 may not be used in a field with asterisk fill specification. When it is it will be interpreted as the end of the field and the start of the next numeric field.

Extra asterisk characters may be used instead of the

II character. For instance,

******** is the same as **111111111111.

For example:

0010 PRINT USING "**1111.1111",123

0020 PRINT USING "**1111.1111-",-123

0030 PRINT USING "**$$$$$-",-2

-RUN

*123.00

*123.00-

*****$2-

0010 PRINT USING "****.1111",123

0020 PRINT USING u**$$ .1111",1

0030 PRINT USING "****",.5678

-RUN

*123.00

**$1.00

***1

6.1.6 Sign Specification

BASIC provides several methods of specifying how to print signed values. As stated above, when the mask field does not specify how to format a negative value, a leading, minus sign is generated. This is unacceptable in many cases and BASIC will not allow it if the format specification includes leading zeros (9), floating dollar sign ($$), or asterisk fill (**). In these situations you must use one of the sign specification characters.

BASIC - 39-

BASIC llERIlDlCE IWmAL

All of the sign specification characters, when used, must appear at the end of format field (if they appear at the beginning or middle of a format field they will be treated as non-formatting characters or field separators, respectively).

Tra~1iDg Sign Speci£~cat~OD

A plus sign character (+) at the end of a format specification indicates that the sign of the field (+ or -) is to be output at the end of the number.

Trai.1f.ng Hinus S~gn Speci£~cat~OD

A minus sign character (-) at the end of a format specification indicates that the sign of the field (-) is to be output at the end of the number if the value of the number is less than zero.

Tra~1iDg Deb~t S~gn Spec~f~cat~OD

Debit specification characters (DB) appearing at the specification indicate that a literal DB is to be output number if the value of the number is less than zero. end of a format at the end.of the

Tra~1ing Credit S~gn Spec~f~cat~on

Credit specification characters (CR) appearing at the specification indicate that a literal CR is to be output number if the value of the number is less than zero. end of a format at the end of the

Angle Bracket Specif~cat~on

An angle bracket the the number character (» at the end of a format specification indicates is to be surrounded with angle brackets if the value of the number is less than zero.

Note that this specification is somewhat different from the other sign specifications in that not only is a character added at the end of the number output but also at the beginning of the number.

This sign specification may not be used with the numeric field specification characters 9, $$, or **.

Negative value specifications may be used with any of the other numeric field formatting characters with the exception of exponential field specification.

- 40BASIC

CHAPTER. 6: FORHATED OUTPUT

Examples:

0010 PRINT USING

0020 PRINT USING

0030 PRINT USING

0040 PRINT USING

0050

0060

USING

-RUN

123+

123

12.00

11111111+" , 123

11111111-

II ,

12 3

IIIIIIIID B

II ,

12 3

IIIIIIIICR

II ,

123

11111111>

II ,

12 3

11I1I1I1I1t1 • 1111>

II ,

0010 PRINT USING

0020 PRINT USING

0030 PRINT USING

0040 PRINT USING

0050 PRINT USING

0060 PRINT USING

-RUN

123-

123DB

123CR

<123>

<12.00>

11111111+

II ,

-123

11111111-" ,-123

IIIIIIIIDB ", -123

IIIIIIIICR ", -123

"11111111>", -123

11I1I1I1I1t1 • 1111>" , -12

6.1.7 Exponent~al F~eld Spec~f~cat~on

BASIC normally prints a number in E format only when it is larger than 13 digits long, for example: 123456789012345 would be printed as 1.234567890123E+014.

However, with PRINT USING or the FORMAT$ you can force a number to be output in E format. This is done with the exponential field specification: ~~~~~.

When a number is to be formatted in E format you cannot specify any other formatting characters other than the number of digits (#) or the decimal point position (.).

The exponential field specification, when used, must be at the end of the numeric field specification: ##.####~~~~~.

The exponential characters when specification. field specification it is known

For example: that may be used with fewer than five up-arrow the exponent will fit in the smaller allows for exponents from -126 to +126 allows for exponents from -99 to +99 allows for exponents from -9 to +9 allows for exponents from a to 9

For example:

0010 PRINT USING "#.##~~~~~",124

0020 PRINT USING "11I1I1I1I1I1I1t1~~~""'~", 123445

0030 PRINT USING "1111111111. 11I1t1t1~""'~""''', 12345678

0040 PRINT USING "#.11t1l1l1l/~~",1234567

-RUN

1.24E+002

12344500E-002

12345.6780E+03

1.23456E6

6.1.8 F~eld Spec~f~cat~on too S.all

When a number field specification does not specify sufficient digit to allow the number to be output a percent symbol character (%) will be output followed by the number, unformatted.

BASIC - 41 -

BASIC REFERERCE IWWAL

This situation can happen for several reasons:

Field isn't large enough: mask= ### number = 1234

Field isn't large enough to include the commas specified: mask= #,### number= 12345

Field isn't large enough to include floating dollar sign: mask= $$### number= 12345

Field isn't large enough to include leading minus sign: mask= H## number=

-123

In the following examples a double field mask is used to print two numbers, the first number won't fit in the first field but the second, identical number will fit in the second field.

0010 PRINT USING

0020 PRINT USING

0030 PRINT USING

0040 PRINT USING

0050 PRINT USING

0060 PRINT USING

0070 PRINT USING

"111111 11111111.1111",1234,1234

"/1,111111/1111111/1",12345,12345

"$$111111 1111111111",12345,12345

"**111111 1111111111",12345,12345

"111111 111111-" ,-123,-123

"11.1111 .................... 1111.1111 .................... ", -1,-1

"11./11, ........ 11.11I1 ................ ",lE+12,lE+12

-RUN

% 1234 1234.00

% 12345 12345

%-123 123-

%-1 -1.00E+000

% 1000000000000 1.00E+12

6.2 String Field Masks

String field masks may only be used for the PRINT USING statement, not in the

FORMAT$ function. A string field mask requires a string value as input. When an attempt is made to use a string field mask with a numeric value the error "[26]

Invalid using" will occur.

The output of a string field specification mask will always be the same length as the length of the specification mask with one exception: extended fields. When a string value is longer than the string field mask BASIC will print as much of the string as will fit and truncate the remaining.

6.2.1 Single Character

You can specify that only the first character of the string value is to be printed by using the single quote character as a single character string mask field.

Alternately the exclamation mark (1) may be used.

0010 PRINT USING "1","ABCDEFGH"

RUN

0020 PRINT USING "''',''XYAX''

RUN

- 42 -

BASIC

CHAPTER. 6: I'ORHATED OUTPOT

6.2.2 Left Justified Field

If you specify a left justified string field, BASIC prints the string starting at the left most position. If there are any unused places, BASIC prints spaces after the string. If there are more characters in the string value than in the string mask, BASIC truncates the string and does not print the excess characters.

To specify a left justified string field use the single quote lead in character (') followed by one or more L characters. The number of L characters (upper or lower case) plus the lead in quote specify the length of the left justified field.

Alternately you may use the back slant character to mark the beginning and end of the string mask. In this form spaces must be used between the two back slant characters. The number of spaces plus the two back slant characters specify the length of the left justified field to be printed.

With either method the minimum string length is two.

For example:

0010 PRINT USING "'L","ABCDEF"

0020 PRINT USING "'LLL","1234567"

0030 PRINT USING "\ \","ABC"

RUN

1234

ABC

0010 PRINT USING "'LLLLL","1234567890"

0020 PRINT USING "'LLLLL","AB"

0030 PRINT USING "\ \","ABCD"

RUN

123456

ABCD

6.2.3 Right Justified Field

If you specify a right justified string field, BASIC prints the string so that the last character of the string is in the right most place of the field. If there are any unused places before the string, BASIC prints spaces to fill the string. If there are more characters in the string value than in the string mask, BASIC truncates the string and does not print the excess characters.

To specify a right justified string field use the single quote lead in characters

(') followed by one or more R characters. The number of R characters (upper or lower case) plus the lead in quote specify the length of the right justified field.

For example:

0010 PRINT USING "'RRRRRR","ABCD"

0020 PRINT USING "'RRRRRR","AB"

0030 PRINT USING "'RRRRRR","ABCDEF"

0040 PRINT USING "'RRRRRR","ABCDEFGHIJKLMNOP"

RUN

ABCD

ABCDEF

ABCDEFG

6.2.4 Center Justified Field

If you specify a centered field, BASIC prints the string so that the center of the string is in the center of the field. If the string cannot be exactly centered,

BASIC - 43

BASIC 1lEFERERCE MANUAL such as a two character string in a five character field, BASIC prints the string one character off center to the left. If the length of the string is longer than the mask field the string will be truncated.

To specify a center justified string field use the single quote lead in character

(') followed by one or more C characters. The number of C characters (upper or lower case) plus the lead in quote specify the length of the center justified field.

For example:

0010 PRINT USING "'CCCCCCCCCC","ABC"

0020 PRINT USING "'CCCCCCCCCC","ABCDEF"

0030 PRINT USING "'CCCCCCCCCC","A"

0040 PRINT USING "'CCCCCCCCCC","ABCDE"

0050 PRINT USING "'CCCCCCCCCC","ABCDEFGHIJKLMNOPQRSTUVWXYZ"

RUN

ABC

ABCDEF

ABCDE

ABCDEFGHIJK

6.2.5 Extended Field

The extended field is the only field that automatically prints the entire string.

When you specify an extended field, BASIC left justifies the string as it does for a left justified field, but, if the string has more characters than there are places in the field, BASIC extends the field and prints the entire string. This extension may cause other items to be misaligned.

To specify an extended field use the single quote lead in character (') followed by one or more E characters. The number of E characters (upper or lower case) plus the lead in quote specify the minimum length of the extended field. The resulting output field will always be at least the length of the mask field.

For example:

0010 PRINT USING "'E-","ABCDEF"

0020 PRINT USING "'EEEE-","ABCDEF"

0030 PRINT USING "'EEEEEEEEEEEEEEEEEEE-","ABCDEFGHIJKLMNOP"

RUN

ABCDEF-

ABCDEFGHIJKLMNOP

6.3 Multiple FieldS In One Mask

The PRINT USING statement allows mUltiple fields to be specified in one mask. When this is done the values of the expressions in the PRINT USING statement are matched in a one to one relation with the fields in the mask. (The FORMAT$ function only allows one numeric field to be specified in the mask. A second field, if specified, will be used to mark the end of the mask.)

- 44 BASIC

CBAPTEIl 6: F01DIATED 01rlPOT

For example:

0010 PRINT USING "111111 11111111 11111111 1111%",1,2,3,4

0020 PRINT USING "999 9999 9999 99%",100,123,5,2

0030 PRINT USING "'RRRRRRRRRR

RUN

1 2 3 4%

111111 'E", "ITEM", 23, "THIS IS THE DESCRIPTION"

100 0123 0005 02%

ITEM 23 THIS, IS THE DESCRIPTION

As mentioned earlier, any non-formatting characters in the mask field are treated as literal characters to be included in the output:

0010 PRINT USING "ITEM 9999 Amount each:

RUN

ITEM 0023 Amount each: $15.40

$$$$$$.1111",23,15.40

6.4 Re-using Mask Fields

The PRINT USING statement will re-use the mask field if there are more values specified as input than there are fields in the mask. BASIC will output a carriage return, line feed each time that the mask is re-used.

For example:

0010 PRINT USING "$$$$$$, $$$ .1111",1,23.4,34,234,5467.2,1235.924

RUN

$1.00

$23.40

$34.00

$234.00

$5,467.20

$1,235.92

6.5 Using Errors

A using error occurs (and a message is displayed) if:

The format string is not a legal string expression.

There are no valid fields in the format string.

A string is printed in a numeric field.

A number is printed in a string field.

BASIC - 45 -

BASIC REFERERCE HARUAL

PJtDIT USIRG and POBHAT$ I'onaat Characters - lI1merlc I'f.elds

Character 1 Function

====================================================================1

9 1 Reserves place for one digit. Also specifies no zero 1

1 suppression. 1

--------------------------------------------------------------------1

# 1 Reserves place for one digit, with leading zeros 1

1 suppressed.

1 Reserves place for one digit and floating dollar sign.

1 Causes leading asterisks to be printed instead of

1 spaces. Also reserves place for two digits.

Causes a comma to be printed between every third digit starting from the decimal point and proceeding from right to left. Also reserves place for one digit.

1 Specifies location of decimal point.

1 Causes a trailing minus sign to be printed when number

1 is negative.

1 Causes a trailing minus or plus sign to be printed

1 depending upon the sign of the number

Causes a trailing DB to be printed when number is negative.

Causes a trailing CR to be printed when number is negative.

Causes a leading, floating < and a trailing > to be printed when number is negative.

Causes the number to be printed in E format. Only allows for single digit, unsigned exponent.

Causes the number to be printed in E format. Only allows for single digit, signed exponent.

Causes the number to be printed in E format. Only allows for double digit, signed exponent.

1 Causes the number to be printed in E format.

- 46 BASIC

CHAPTEll 6: FOllHADD OUTPOT

PRIRT USIRG Foraat Characters String F~elds

Character

Function

I===========================~========================================

I I Single character field printed.

\ I Marks beginning or ending of a left justified field

I and reserves one place for a character.

Single character field printed or treated as the lead in character for following four format characters and reserves one place for a character.

L I Causes string to be left justified and reserves place

I for one character. Also lower case 1.

Causes string to be right justified and reserves place

I for one character. Also lower case r.

Causes string to be center justified and reserves

I place for one character. Also lower case c.

E Causes string to be left justified, reserves place for one character, and causes entire string to be printed. Also lower case e.

BASIC 47 -

CBAPTEIl 7

USIBG FILES

BASIC supports file input and output to the on-line disk drives, console, printers, and other devices. Various file access methods are supported: SEQUENTIAL (one record after another from beginning of file); DIRECT (random by relative record number); and INDEXED (random by key).

Files have· both an external name by which it is known within the system, and an internal file designator used within the BASIC program. For example, a file might exist on a disk, with the name INVEN.MASTER. This is the external name (i.e.,

INVEN.MASTER:A). In the BASIC program it might be opened on channel 1. This is done through the OPEN statement. All further references to the file in the program will be to #1 not to the file name of 'INVEN.MASTER:A'.

There are sixteen (16) channel numbers available to the user program, and all sixteen may be in use at one time. This means that there can be sixteen data files available for use at anyone time in the BASIC program. Each open I/O channel requires buffer space and a small amount of space used for pointers, etc. The amount of buffer space needed varies, depending upon the device.

A seventeenth channel is always open to the CONSOLE. This channel is only accessed with INP and EOF functions, and the INPUT, LINPUT, and PRINT statements.

The sequence of statements in a BASIC program that uses a file is:

OPEN

INPUT, LINPUT, PRINT, READ, WRITE, etc.

OPEN This statement must be used before other file access statements to specify the file to be used, the internal channel to use for the file, the access mode and method, and various options that are to be used with the file.

INPUT,PRINT These statements perform the input and output to the file. They are performed as often as necessary to accomplish the function of the program.

The specific statement to be used depends upon the access mode used in the

OPEN statement and the file format.

CLOSE This statement is used last to designate that the operations to that file are complete.

7.1 Access Hode

There are three types of access modes that may be specified with the BASIC OPEN statement.

INPUT This mode indicates that the file is to be used for input operations only.

When this mode is in effect BASIC will not allow output type operations to be performed on the file's I/O channel.

OUTPUT This mode indicates that the file is to be used for output operations only. BASIC will not allow input type operations to be performed on this file's I/O channel. This mode is normally used when a file is first being built or created or on output only devices like a printer.

- 48BASIC

CBAPTEIl 7: USIBG I'ILES

UPDATE This mode allows both input and output operations to be performed on the file.

7.2 Access Methods

The OPEN statement requires that you specify the access method. Do not confuse this with the file's format even though the same adjectives are used for both. The access method specifies the type of access to be performed on the file which may be quite different from the format of the file.

SEQUENTIAL Indicates that the records in the file are to be read or written sequentially, one after the other, starting at the beginning of the file.

With this access method, to access any specific record, all records before that record must be accessed.

DIRECT Indicates that the records in the file are to be read or written randomly, by record number. This access method allows any record in the file to be accessed without accessing any other record in the file (i.e., directly).

INDEXED Indicates that the records in the file are to be read or written randomly, by record key. This access, similar to DIRECT, allows any record in the file to be accessed without accessing any other record in the file; however, the record is accessed using a generic key, or name, of the record.

7.3 File Formats

A file's format is determined when the file is first created. The OASIS operating system supports three types of data file formats:

SEQUENTIAL This file format is similar to a tape file, that is, a record can only be added at the end of the file and a record can only be accessed after all records preceding it have been accessed sequentially.

DIRECT

Sequential files exist naturally on CONSOLE terminals, PRINTERs, TAPEs, and COMMs.

A direct file is a file of fixed length, fixed number of records. Records are accessed in a completely random sequence by specifying a relative record number.

This file format is quite useful for frequently accessed master files that have sequentially numbered keys such as a customer file or a vendor file.

Access to this type of file is fast, as the system can compute the address of the record on the disk without searching a separate index.

Direct files are only supported on disk devices, and must be created with the CSI command CREATE.

Direct files may be accessed with SEQUENTIAL or DIRECT access methods.

INDEXED The indexed file format is essentially an indexed file type in addition to a sequential access mode. Records are maintained and accessed with a string key of variable length. Records can also be accessed in a sequential method by use of the READNEXT statement.

BASIC ltEFERERCE HARUAL

Because of the necessity of keeping the index in sequence, updating this type of file is slower than using the direct file format.

Indexed files are only supported on disk devices, and must be created by the CSI command CREATE.

Indexed files may only be accessed with INDEXED access methods.

7.4 Record Allocation Requirements

Since indexed and direct files must be preallocated by the user before the BASIC program can access them it is necessary for the user to calculate the maximum record size required for each file. To do this the user must determine the field types to be written to the file.

For each string field in a record the user must allocate space for the length of the longest field plus 2.

For each floating point field in a record the user must allocate space for 9 positions.

For each integer field in a record the user must allocate space for 3 positions.

Thus the record size for the following direct file must be 32:

WRITE IIl,N:"RECORD",1,2,A,B

7.5 Hulti-Dser File Protections

A BASIC program run on a multi-user OASIS system will operate the same as on a single user OASIS system, except that file contention may occur. This means that two users may attempt to access the same file or the same record in a file at the same time. This situation may, or may not be allowed, depending on the file protections used by the two programs.

A program that does extensive input and output to a file should lock the entire file from other user's use. This is done by specifying the LOCK option in the OPEN statement.

If a file is not locked in its entirety other users may access the file (unless the other user attempts to lock the entire file which would not be allowed).

When a file is it is possible user's program the file. opened for INPUT or OUTPUT no record locking will be perfor.med and that a record read by your program might be updated by another without your program's knowledge. This could result in errors in

When programming in a multi-user system the programmer must always ask the question: What happens if another user wants this record? and program accordingly.

- 50BASIC

CBAPDIl 8

COIIHAImS

BASIC commands are used used in the command mode.

(-)

. to enter, change, and debug programs. They only may be

Command mode is when BASIC prompt character is displayed

BASIC command functions may be divided into four categories:

A. General

HELP - Display list of commands available.

LENGTH - Display current memory utilization of program.

NAME

NEW

- Display or change name of program in memory.

- Initialize BASIC work area, new program.

B. Editing

AUTO - Automatic line number prompting for new line entry.

BOTTOM - Position to the last line in the program.

CHANGE - Change string in one or more lines of code.

DELETE - Remove line(s) of code from program.

DOWN - List next line.

INDENT - Perform standard program indentation.

LIST - List one or more lines of program.

LOCATE - Locate line containing string.

LPLIST - List one or more lines of program on printer.

LPXREF - List cross reference table on printer.

MODIFY - Character by character change of one or more lines.

RENUMBER - Renumber all or part of program.

TOP - Position to the first line in the program.

XREF

- List prior line.

- List cross reference table on terminal.

BASIC - 51 COHHARDS

BASIC REFEIlERCE HABUAL

C~ Disk programs

LOAD

RUN

- Retrieve program from disk.

- Execute program from disk or already in memory.

SAVE - Save current program on disk.

D. Debugging

BREAK - Specify condition to break on.

CONTINUE - Resume execution.

STEP - Execute next statement and stops.

TRACE - Display line numbers executed and optionally variables· changed.

UNTRACE - Discontinue trace mode.

UNBREAK - Remove one or all breakpoints set.

VARS - Display contents of all variables defined.

COlUWIDS - 52 BASIC

CIIAPTEIl 8: COJIHANDS

8.1 AD'l'O em.and

1 AIJ'lO

2 AD'l'O <start>

3 AUtO <start> <~cre.ent>

Where:

Purpose:

The AUTO command allows you to enter new lines to the program with automatic line numbering.

C~nt:

The AUTO command cannot be used if a program in memory is read protected (see LOAD command) •

The AUTO command is intended to be used for creating new programs or adding new sections to an existing program in memory.

The <increment> value, when specified, sets the current increment value for this

AUTO and subsequent executions of the AUTO command.

When the AUTO command is executed BASIC will display the current line number plus the current increment on the console (or the <start line number>, when specified) followed by a space. You may then enter a program line. After a program line has been entered and terminated by a carriage return, the line number is incremented by the current increment and the process is repeated.

To terminate the line input process enter a carriage return when BASIC prompts you with the line number. No blank line will be added to the program. Lines entered with this command cannot replace any line in the program with the same line number nor can it be used to add multiple lines that merge around existing lines. In order to add lines that merge around exising lines you must enter them one at a time.

BASIC - S3-

BASIC REl'ERERCE IWWAL

===================================================================================

Examples:

-LIST

10 INPUT "RADIUS OF CIRCLE",RR

20 PRINT "DIAMETER ="j2*R

30 PRINT "AREA ="jPI*R ..... 2

40 PRINT "CIRCUMFERENCE ="j2*PI*R

50 END

-DELETE 10 20

TOF:

-AUTO

10 PRINT "HELLO"

20 LET R=55

AUTO cannot replace or merge lines

-LIST

10 PRINT "HELLO"

20 LET R=55

30 PRINT "AREA =";PI*R ..... 2

40 PRINT "CIRCUMFERENCE ="j2*PI*R

50 END

-DELETE 50

40 PRINT "CIRCUMFERENCE ="j2*PI*R

-AUTO 50,3

50 PRINT "AGAIN"j\INPUT Y$

53 IF Y$="Y" THEN 20

56 END

-LIST

10 PRINT "HELLO"

20 LET R=55

30 PRINT "AREA ="jPI*R .... 2

40 PRINT "CIRCUMFERENCE ="j2*PI*R

50 PRINT "AGAIN"j\INPUT Y$

53 IF Y$="Y" THEN 20

56 END

-AUTO

59 REM Exit routine

62 QUIT 4

Note that the current line and the increment value are unchanged because no start line nor increment value was specified.

===================================================================================

AUTO - S4 BASIC

CHAPTER 8: COHHANDS

8.2 Bottom Com.and

BOTTOM

Purpose:

The bottom command positions to the last line in the program and displays that line of code.

Comment:

The bottom command cannot be used if the program in memory is read protected (see

LOAD command).

===================================================================================

Examples:

Stop at line 0020

-BO

999 END

===================================================================================

BASIC - SS -

BASIC REFERERCE HABUAL

8.3 BREAK Command

1 BREAK

2 BREAK [AT] <line reference>

3 BREAK [AT] <line reference> [AFTER] <count>

4 BREAK [OR] <variable>

5 BREAK [OR] <variable> CHARGE

6 BREAK [OR] <variable> AFTER <count>

7 BREAK [OR] <variable> CHARGE AFTER <count>

8 BREAK [OR] <variable> <relation> <value>

Where:

<value>

::=

::= <numeric literal>

See also: STEP, TRACE, UNBREAK, UNTRACE, and VARS commands

Purpose:

The BREAK command provides the capability of dynamic debugging of the BASIC program.

Comment:

<count> is a numeric value referring to the number of times that the specified break condition is to occur before a break is actually performed.

<variable> is a simple numeric variable, not a subscripted variable. An array name is acceptable.

Format 1 of the BREAK command will display the current break table.

Format 2 will cause a break to occur at the next execution of the statement on the line referenced, before the statement is executed.

Format 3 will cause a break to occur at the <count> execution of the statement on the line referenced, before the statement is executed.

Format 4 will cause a break to occur the next time that the <variable> is used,

BREAK - 56 BASIC

CHAPTER. 8: COIIHAIIDS after the statement using the variable is executed.

Format 5 will cause a break to occur the next time that the <variable> is changed by a statement, after the statement changing the variable is executed.

Format 6 will cause a break to occur after the <variable> is referenced <count> times, after the statement referencing the variable the <count> time is executed.

Format 7 will cause a break to occur after the <variable> is changed <count> times, after the statement changing the variable the <count,> time is executed.

Format 8 will cause a break to occur when the relationship is true, after the statement causing the relationship to become true is executed.

The BREAK command may be abbreviated to the letter B.

When a break occurs, execution of the program stops and the message "Break at " or "Break on •••• " is displayed. Control returns to the command mode. When a break occurs on a variable reference or change the statement causing the break will be completly executed. Executing a CONTINUE command will cause the statement following to be executed.

Only one break will be set for a specific variable or line at one time. When multiple break points are attempted to be set for a variable or a line only the last one specified will be in effect.

Note: Break points are only cleared by the UNBREAK, NEW, and LOAD commands. During execution, if a different program is brought into memory the old break points will still exist. The RUNUMBER command does not change the line numbers specified in any break points.

BASIC ~57 BREAK

BASIC 1lD'EIlDICE IW1UAL

===================================================================================

Example:

-LIST

10 FOR 1%=1 TO 4

PRINT 1%

GOSUB SUM

40 NEXT

50 GOTO 9999

60 SUM: TOTAL% = TOTAL%+I% RETURN

9999 END

-BREAK AT SUM

-BREAK ON 1% CHANGE AFTER 4

-BREAK

Break at SUM

. Break on 1% changed after 4

-RUN

Break at line 60

-VARS TOTAL%

TO TAL % = 0

-VARS 1%

1% =

-UNBREAK AT SUM

-CONTINUE

Break on 1% at line 40

-VARS I%,TOTAL%

1% = 4

TOTAL% = 6

===================================================================================

'..

- 58- BASIC

8.4 CHARGE Com.and

1 CHARGE

2 CHARGE <Char><from string><Char><to string><char>

3 CHARGE <Char><from string><Char><to string><char><range>

Where:

<range>

::= <string>

::= <line number>[ <line number>]

/------------------------------------------------------/

/ RUN / Closed / Cleared / Cleared /

/ CHAIN / Closed / Cleared

/ Not cleared /

/ LINK / Not closed / Cleared / Not cleared /

===================================================================================

Examples: Explanation:

0010 CHAIN "SEGMOl"

0030 CHAIN "SEGMO"&NUM(I)&":S"

Program named 'SEGMOl' will be loaded, all files will be closed,

& control will pass to the first statement of 'SEGMOl'.

When I equals 1, this statement is the same as example 10.

If I is equal to 3, program

'SEGM03' will be executed, etc.

Incorrect example: Explanation:

0010 CHAIN "SEGMENT-I" Program name can only be 8 characters long. Also, - is invalid.

Line labels are not allowed. 0020 CHAIN "PROGRAM" LABEL

===================================================================================

BASIC - 103 -

BASIC B.EFERERCE HANUAL

9.4 CLEAR Statement

1 CLEAR

2 CLEAR <variable list:>

Where:

<variable list> ::= <numeric variable>[,<variable list>]

<string variable>[,<variable list>]

<array name>[,<variable list>]

See also: CHAIN, COMMON, LINK and RUN statements

Purpose:

The CLEAR statement initializes the working storage area.

Comment:

The CLEAR statement effectively erases all variable names and their contents from memory.

Variables defined as COMMON variables are not erased by this command.

This operation is performed automatically whenever a CHAIN, LINK, LOAD, NEW, or RUN command is executed. It may be necessary to use this separate command when there are many variables defined in working storage that are not going to be used again, and there are no variables whose loss would be detrimental to program execution.

The main advantage continue execution available. gained that, is a fresh without it, work area that may allow the program to might have required more memory than

Optionally this statement may clear specific variables (or complete arrays) from memory when they are no longer needed by the program.

===================================================================================

Examples: Explanation:

0010 CLEAR

0020 CLEAR A,B,INDEX%

0030 CLEAR ARRAYl$,A,B

All variables are cleared from memory.

Only the variables A, B, and INDEX% are cleared from memory (unless they were defined as COMMON).

The entire array ARRAYl$ is erased from memory along with the variables A and B.

===================================================================================

CLlWt 104 BASIC

CIIAPTER. 9: STATIIIERTS

9.5 CLOSE Statement

1 CLOSE '<channel>

Where:

See also: CHAIN, CSI, END, MOUNT, OPEN, QUIT and RUN statements

Purpose:

The CLOSE statement is used to terminate I/O between the BASIC program and a data file.

C~t:

The CLOSE statement causes the output of the last block of data to the file.

Execution of a CHAIN, END, or CSI statement automatically closes all open files.

The RUN command automatically closes any open files before execution begins. The'

QUIT command will close any open files before exiting BASIC.

The <channel> must have the same value as that used with the OPEN statement.

Once a file has been closed, it may be reopened on any available channel number.

If the user should happen to abort a BASIC program (by an IPL or power failure)

When indexed or sequential files are open, errors may exist in the file directory or in the file itself. It is acceptable to abort the program by using the Program

Cancel-key or the System Cancel-key, but exiting by a system reset button or power failure can be disasterous.

===================================================================================

Examples:

0010 CLOSE 111

0020 CLOSE IIINPUT%

Explanation:

File opened on channel one is closed.

File opened on channel corresponding to value of variable INPUT% is closed.

Incorrect examples:

0010 CLOSE "IVY MASTER A"

0020 CLOSE 114,115,116,1110

0030 CLOSE 1117

Explanation:

File names are not allowed.

Multiple channels not allowed.

Channel 17 is invalid.

===================================================================================

BASIC - lOS CLOSE

BASIC BEFERERCE MANUAL

9.6 COBMON Statement

1 COMMON <variable list>

Where:

::=

<simple variable>[,<variable list>]

<dim variable>[,<variable list>]

::= <array name>«dimension>[,<dimension>])

See also: CLEAR, DIM, OPTION, and RUN statements

Purpose:

The COMMON statement allows you to specify that certain variables are shared between segments of a program and are, therefore, not to be cleared.

Comment:

The COMMON statement must be the first statement on a line--there can be no line label specified on the same line as a COMMON statement.

The COMMON statement is an executable statement, similar to the DIM statement--in fact, it must be executed before any references to the variables it is defining as common are made.

When a program is RUN, CHAINed to, or LINKed to, the entire program is scanned for any and all COMMON statements. When one is found the variables specified on that statement are searched for in the COMMON variable storage. When a variable is found it will be left as is. When a variable is not found in the COMMON variable storage area it will be defined or dimensioned in that area.

Note: If a variable was used in a previous program but not defined as COMMON before its use, the value will not be retained at the time it is defined as COMMON.

Although it is not necessary to re-define all of the variables that are COMMON between programs it is definitely a good programming practice. It is also not necessary to specify the variables in a COMMON statement in the same sequence as they might have been defined in a previous program's COMMON statement--variables are accessed by name, not location or sequence.

===================================================================================

Examples: Explanation:

0010 COMMON A,B,A%

0020 COMMON ARRAY$(5,22),CONTROL

The variables A, B, and A% were defined, or will be used, by another program.

Similar to above but also dimensions ARRAY$

================~===================================== =============================

COHHON - 106 BASIC

CHAPTER 9: STATDIERTS

9.7 CSI Statement

1 CSI <St~-ezp>

Purpose:

The CSI statement allows the BASIC program to execute any OASIS command, resuming execution of the BASIC program afterwards.

CODDDeut:

All I/O channels will be closed when the CSI statement is executed.

<String-exp> is any valid OASIS command, with all arguments and options required by the specific command. Refer to the OASIS System Reference Manual for complete specifications of these commands.

When the first character of <string-exp> is the ">" displayed on the console device, otherwise the

(command executed in "silent" mode). character, the string will be string will not be displayed

When the CSI statement is executed your BASIC program and all of its work areas are marked as protected memory. A special call to the operating system passes the string expression to the Command String Interpreter which executes the desired program. Upon completion of that program the operating system reloads the BASIC or

RUN command, if necessary, unprotects the memory area containing your program, and continues execution of your program.

The CSI statement should not be used to execute large OASIS commands because of the restricted memory available. Additionally, when the following commands are executed the result will be unpredictable: DEBUG, ASSEMBLE, BASIC, and RUN. The

ATTACH program cannot be called to attach a new device driver; however, it may be called to change some options on a currently attached device. In addition the stack of the EXEC language must be empty.

===================================================================================

Examples: Explanation:

0010 CSI "LIST CUSTOMER MASTER (PRINT NOHEAD)"

The file CUSTOMER MASTER is printed without headings.

0015 A$=">filelist a (exec append)"

0020 CSI A$ Command is displayed. The file named SELECTED.EXEC is appended with the current filelist from the directory of the A disk.

===================================================================================

BASIC - 107 CSI

BASIC JlEI'ERERCE IWWAL

9.8 DA7& Statement

1 DATA <data Hst>

Where:

::=

<data element>[,<data list>]

------

10 FOR 1 TO 50 STEP 2

20 FOR X = 1 STEP -3

30 FOR J = 5 TO 1 STEP 2

40 FOR K = 1 TO 4 STEP -5

10 FOR I

20 FOR J

Explanation:

Index variable missing.

Limiting expression is missing.

Loop will fail initial test.

Illegal nesting.

---+--

50 NEXT I

90 NEXT J

------

10 FOR I •

Note that lines cross here.

Illegal nesting.

60 FOR I

90 NEXT I

100 NEXT I There is no open FOR loop

===================================================================================

BASIC - 119 FOB.

BASIC BEI'EIlERCE IWmAL

9.16 GET State.ent

1 GET DEVICE <devi.ce number>, <vadable list>

2 GET HEHORY <address>,<vadable Ii.st>

3 GET PORT <port>,<vadab1e list>

Where:

::= <numeric expression>

<variable list> ::= <numeric variable>[,<variable list>]

<string variable>[,<variable list>]

1------------------------------------------------------I

RUN

Closed

Cleared

CHAIN

LINK

Closed

Cleared

Not closed

Cleared

Not cleared

===================================================================================

Examples: Explanation:

0010 LINK "SEGMOl"

0020 LINK NAME $ (INDEX%)

0030 LINK "SEGMO"&NUM(I)&":S"

Program named 'SEGMOl' will be loaded and execution resumes at the first line.

The program indicated by the contents of the string array variable NAME$, subscript INDEX will be loaded and execution will resume at the first line.

When I equals 1, this statement is the same as example 10. When I equals

3 program 'SEGM03' will be executed, etc.

Incorrect example: Exp lana tion :

0010 LINK "SEGMENT-I" Program name can only be 8 characters long. Also, - is invalid.

===================================================================================

BASIC . - 135 LIBx:

BASIC 1lDERBRCE IWfOAL

9.24 LIRPOr State.ent

1 LIRPOr <string var:iable>

2 LIRPOr <prOllpt>. <string varf.able>

3 LIRPOr '<channel>: <string varf.able>

4 LIRPOr '<channel>. <key>: <str1.Dg varf.able>

Where:

::= <numeric expression>

::= <string literal expression>

See also: INPUT, LINPUT USING, MAT INPUT, MAT READ, READ, and READNEXT state/

Purpose:

The LINPUT statement allows entry of an entire line of data as a single character string, including spaces and punctuation.

Co...ent:

The LINPUT statement operates identically to the INPUT statement with one exception: only one variable may be specified for input and the variable must be a string variable.

===================================================================================

Examples: Explanation:

0010 LINPUT A$ Prompt character(s) is displayed at the current cursor position, program execution is suspended until the operator terminates

0020 LINPUT "NAME",A$

0030 OPEN the input.

The literal "NAME? " is displayed, execution is suspended until the operator terminates input.

111: "CONSOLE", INPUT SEQUENTIAL

0040 LINPUT #1: STRING$ Similar to line 10 but no prompt nor

0050 OPEN 112: "DATA. FILE" , INPUT DIRECT

0060 LINPUT #1,5: RECORD$

INP capabilities.

Record number 5 of file is read into variable RECORD$

LIRPUT 136 BASIC

CIIAPTER. 9: STATllllERTS

Incorrect Examples:

0020 LINPUT Al

0030 LINPUT A$,B$,C$

Explanation:

Must be a string variable.

Only one variable is allowed.

===================================================================================

BASIC - 137 LDIPD'r

BASIC REFERENCE IWWAL

9.25 LIRPUT USIRG Statement

1 LIRPOT USIRG <string l~teral ezpress~on>,<Str~ variable>

2 LINPUT <prompt>,USIRG <str~ l~teral ezpress~on>,<str~ va~ble>

3 LIRPOT USIBG <str~ ezpress~on>,<string va~ble>

4 LIRPDT <prompt>,USIRG <string express~on>,<string variable>

Where:

See also: INPUT, LINPUT, MAT INPUT, MAT READ, READ, and

READNEXT statements

Purpose:

The LINPUT USING statement allows entry of an entire line of data from the console as a single character string, including spaces and punctuation, with length control and the ability to "modify" an existing field.

COIIIIDe1lt:

The LINPUT USING statement, similar to the LINPUT statement discussed previously, allows entry of an entire line of text, including any embedded quotes and commas, as one string field. Similarly, the LINPUT USING allows a prompting message to be displayed before accepting input.

However, unlike the LINPUT statement, the LINPUT USING statement provides greater control of the terminal display by limiting the number of characters input. The most significant feature of the LINPUT USING statement is that the operator can make corrections to the line being entered without re-entering the entire line.

Formats 1 and 2 of the LINPUT USING statement use a <string literal expression> as the using mask. A <string literal expression> is a string expression that starts with a string literal. For example: ""&SPACE$(lO) is a string literal expression of length 10.

With either of these formats the statement will display the prompting message if specified. The input area is the area from the starting position for a length specified by the length of the string literal expression.

If the first character of the string literal expression is an exclamation mark (1),

BASIC will perform an auto carriage return when the input area if filled. This is generally used on single character input lengths.

Formats 3 and 4 of the LINPUT USING statement use a <string expression> as the using mask. With either of these formats the statement will display the prompting message if specified, then display the string expression in the input area. The input area is the area from the starting position for a length specified by the

LIRPDT USIBG - 138BASIC

CHAPTER 9: STADIIERTS length of the statement will input. string expression. Additionally, these formats of the LINPUT USING copy the string expression into the input variable before accepting

At this point all four formats of the LINPUT USING statement act the same with the difference being that formats 3 and 4 have pre-filled the input area with the using mask and formats 1 and 2 have a null string in the input area. The operator may enter any ASCII character into the input area. A carriage return will cause the contents of the variable to be saved and execution of the program resumes.

Certain keys are available to the operator to make editing changes:

<carriage return> Terminates entry.

<right arrow> Is a non-destructive advance. l~en this key is entered (or its equivalent: CTRL/F) the cursor will be advanced over the next character.

<left arrow> Is a non-destructive back space. When this key is entered (or its equivalent: CTRL/H) the cursor will be backed over the current character.

<rub out> Is a destructive back space. When this key is entered the cursor is backed up one position and that character is replaced with a space.

<CTRL/D> Is a destructive delete. ~en this key is entered the current character is deleted and the remaining characters in the input area are shifted one character to the left.

<CTRL/I> Is a "destructive" insert. When this key is entered (or its equivalent:

<tab» the remaining characters in the input area are shifted one character to the right and a space character is inserted at the current position. If a character shifting to the right would exceed the input area length it will be deleted.

Any other character entered by the operator will replace the current character.

Unfortunately, this statement is difficult to illustrate with a printed example.

Therefore, the following program is provided for you to execute so that you may see its uses. Keep in mind that what you see on the terminal in the input area is what is actually in the field being entered.

Any control character (ASCII value less than 32) will terminate the entry and will set the INP function to that value. This implies that the control characters 4, 6,

8, 9, 13 cannot be used as user defined control keys from a LINPUT USING statement.

This does not apply to the INPUT or LINPUT statements.

BASIC - 139 LIBPOT USIBG

BASIC RD'ERERCE HABtJAL

===================================================================================

0010 OPTION PROMPT 'UI, CASE "M"

0020 PRINT CRT$("CLEAR")

0030 PRINT "The following is a simple illustration of the LINPUT USING"

0040 PRINT "statement in both of its primary forms. The first input request"

0050 PRINT "will use the statement with a string literal expression of"

0060 PRINT "length 30. The second input request will use the statement with"

0070 PRINT "a string expression of length 30. The contents of the string"

0080 PRINT "expression will be the field entered by the first input request,"

0090 PRINT "padded to the proper length."

0100 OPTION CASE ''M'' PRINT AT$ (1,10) ;CRT$ ("EOS");

OllO·PRINT AT$(l,lO);"Input 1: [";SPACE$(30);"]";AT$(11,10);

0120 LINPUT USING ""&SPACE$(30),FIELD$

0130 PRINT AT$(1,12);"Input 2: [";SPACE$(30);"]";AT$(11,12);

0140 LINPUT USING RPAD$(FIELD$,30),FIELD$

0150 PRINT AT$(1,14);"The field you entered contains:"

0160 PRINT"

0170 OPTION CASE "U"

I";FIELD$;" I";

0180 LINPUT ""&AT$(1,16)&"Okay to repeat (yIN)? N"&CRT$("Lff),USING "!",ANSWER$

0190 IF ANSWER$="Y" THEN 100 ELSE END

===================================================================================

LIBPDT USDG - 140 BASIC

CIIAPTEJl. 9: STATIIIEND

9.26 MAT Statement

1 MAT <array n.mae>

:II:

<array name>

2 MAT <array D.8BM!> = (<express1.on»

°

I/O

1=======================================1

CONSOLE

PRINTER[n]

1 TAPE en]

COMM[n]

1 x i i

1 X I x i i

/ READER / X I 1 I

1 PUNCH

DUMMY

1 I x i i

=========================================

Duk l'~le fODl8.t/Hode, Hethod R.eI.at~ODShips

==========================================================================

1 mode method / sequential format / direct format 1 indexed format /

/------------------------------------------------------------------------1

/ INPUT SEQUENTIAL

1 INPUT DIRECT

1 file must exist 1

1 N/A /

/ 1 x i i

/ INPUT INDEXED 1 N/A 1 1 X 1

/ OUTPUT SEQUENTIAL / file recreated

/ OUTPUT DIRECT 1 N/A

I I x i i

1 X 1 / OUTPUT INDEXED / N/A /

1 UPDATE SEQUENTIAL 1 file recreated

/ UPDATE DIRECT 1 N/A

1 1 x i i

1 UPDATE INDEXED / N/A 1 1 X /

==========================================================================

===================================================================================

Examples:

0010 OPEN

0020 OPEN

0030 OPEN

0040 OPEN

0050 OPEN

0060 OPEN

0070 OPEN

0080 OPEN

111: ''MAs T • DATA : A" , INPUT SEQUENTIAL

111: "",INPUT DIRECT

115: "TEST.DATA:C",OUTPUT DIRECT

III: "PRINTER", OUTPUT SEQUENTIAL, FORMAT

118: F$&":S",UPDATE INDEXED,LOCK

1116: "CONSOLE",OUTPUT SEQUENTIAL

1115: "PRINTER", OUTPUT SEQUENTIAL

114:

"PRINTER.FILE:S",OUTPUT SEQUENTIAL,EXTEND,FORMAT

===================================================================================

OPES BASIC 160 -

CHAPTER. 9: STATEMENTS

9.36 OPTION Statement

1 OPTION BASE <base value>

2 OPTION CASE <case mode string expression>

3 OPTION PROMPT <prompt>

4 OPTION usa

<usr-name>

Where:

<base value> ::= 0

::= ''M''

"U"

"L"

::= <string expression>

<usr-name> ::= <string expression>

1------------------------------------------------------I

RUN

Closed

Cleared

CHAIN Closed Cleared Not cleared

1 1 1 I

LINK

Not closed

Cleared

Not cleared

===================================================================================

Examples:

-LOAD TEST

-RUN

-RUN TEST

1000 RUN

1010 RUN "JOE"

Explanation:

Program "TEST" is loaded, then executed.

Same as above.

Re-execute program in memory.

Execute program named "JOE".

Incorrect examples

10 RUN PROGRAM

20 RUN "PROGRAM" LABEL

Explanation

Program name must be an expression.

Line labels not allowed.

===================================================================================

BASIC - 185 ROB

BASIC REFERENCE HANUAL

9.50 SELECT State.ent

1 SELECT

2 SELECT <expression>

See also: CASE, CEND and OTHERWISE statements

Purpose:

The SELECT statement defines the start of a SELECT-CASE-CEND programming structure.

CODllllent:

Format 1 of the SELECT statement specifies that subsequent, matching CASE statements will specify the complete relational expression that must evaluate true for the statements following to be executed.

Format 2 of the SELECT statement specifies the expression that is to be compared with the expression of subsequent, matching CASE statements.

SELECT structures may be nested to any depth.

The SELECT-CASE-CEND programming structure is a powerful aid to the programmer wishing to write structured programs in BASIC, a language that doesn't lend itself to structured programming techniques. (Also see ON ERROR, FOR-NEXT, IF-IFEND, and

WHILE-WEND structures.)

===================================================================================

Examples:

3000

3010

3020

3030

3040

3050

3060

3062

3064

3070

3080

3090

3110

3120

3130

SELECT RADIUS*2.*PI

CASE 0

SELECT

CASE SUBVALUE%=20

CASE 1-14

CASE J

CEND

CASE SUBVALUE%>32

CASE ERROR%

CEND

Expianation:

Define VALUE

Perform only if VAI.,UE=O

Perform only if VALUE=O and SUBVALUE%=20

Perform only if VALUE=O and SUBVALUE%>32

Perform only if VALUE=O and ERROR%<>O

End of nested SELECT structure

Perform only if VALUE=I-14

Perform only if VALUE=J%

End of SELECT structure

===================================================================================

SELECT - 186 BASIC

CIIAP"lER. 9: SrATEIIEln'S

9.51 SLEEP Statement

1 SLEEP <integer expression>

Purpose:

The SLEEP statement causes BASIC to pause for a period of time, allowing the operator time to read a message, etc.

Ccmment:

The value of <integer expression> is rounded up and integerized. The value of this expression must be between 0 and 32767 (approximately 9 hours), inclusive.

The minimum time that the SLEEP statement will pause is one second. Specifying any value less than one will be interpreted as the default, one second.

===================================================================================

Examples

10 SLEEP 10

95 SLEEP X/4

200 SLEEP .5

Explanation

Suspend processing for 10 seconds.

Wait for one fourth of X value.

Wait for one second.

===================================================================================

BASIC - 187 SLEEP

BASIC ItEl'EREllCE HABtJAL

9.52 smp State.ent

1 smp

2 smp <expression>

°

(zero) is interpreted as the current system date.

Example: PRINT DATE$ (10);" ";DATE$ (0);" ";DATE$ (28262)

01/10/00 05/15/78 05/18/77

DTE$(<string-exp» Validates the string expression for a valid date. If the string is valid, the standard date format is created for that date. If the string is invalid, a null string is generated. A date may contain: digits, ., /, -. The standard date format is mm/dd/yy •

The standard date format includes leading zeros.

Example: PRINT DTE$("7/6/76"),DTE$("2/30/76"),DTE$("112154")

07/06/76 11/21/54

EXT$(<String-exp>,<num-expl>,<num-exp2» Returns with the subfield of the string expression whose position in string is indicated by the values of the two numeric expressions. The string returned is the subfield of the string whose position is the <num-exp2> subfield of

<num-exp1> subfield.

Example: B$ =AAAA~BBBB~C1C1C1]C2C2C2]C3C3C3~DDDD

PRINT EXT$(B$,2,0)

BBBB

PRINT EXT$(B$,3,3)

C3C3C3

PRINT EXT$(B$,3,0)

C1C1C1]C2C2C2]C3C3C3

PRINT EXT$(EXT$(B$,3,0),1,2)

C2C2C2

As illustrated, when the second numeric expression is zero the entire field referenced by the first numeric expression is extracted. When the field designated by two numeric expressions does not exist in the string, a null string is returned.

BASIC - 209 STJl.IRG mNCTIOBS

BASIC REFERENCE HARUAL

FORMAT${<n~>,<String-exp» This function has the same capabilies as the PRINT

USING statement in regards to the formating of numeric values.

The two expressions are evaluated and the numeric value is forma ted according to the masking characters in the string expression.

Leading asterisk fill.

Leading floating dollar sign.

Trailing literal of DB for negative values only.

Trailing literal of CR for negative values only.

Number surrounded with angle brackets

«»

for negative values only.

Digit position with leading zero suppression.

Digit position with leading zero fill.

Trailing sign for positive and negative values.

Trailing minus sign for negative values only.

Normalize number with commas every three digits.

Use exponential format with single unsigned digit exponent ••

Use exponential format with signed single digit exponent.

Use exponential format with signed double digit exponent.

----- Use exponential format with signed triple digit exponent.

Example: PRINT FORMAT $ (23, "99999") ; FORMAT $ (23, "1111111111")

00023 23

PRINT FORMAT $ (23, "**111111") ;" "; FORMAT $ (123456.78, "$$11, II

***23 $123,456.78

PRINT FORMAT$ (12345, "11.1111111111"'''''')

1.2345E4

PRINT FORMAT$ (-12345.67, "11,111111111111.1111>")

<12,345.67>

For more information and examples see the chapter "Formatted

Input & Output" in this manual.

HEXOF$

(<n~» The numeric expression is evaluated, integerized and translated into the string of characters representing the value in hexadecimal. A four character string is always generated.

Example: PRINT HEXOF$(94);" ";HEXOF$(23129)

005E 5A59

INS${<string-expl>,<n~I>,<n~2>,<String-exp2» This function inverse of the EXT$ function, that is, it inserts into a string. The substring <string-exp2> will after the subfield designated by the values of the expressions. It is important to note that the field after the one designated. a is the subfielq be inserted two numeric is inserted

Example: B$ = AAAA"'BBBB"'C1C1C1]C2C2C2]C3C3C3"'DDDD

PRINT INS$(B$,2,0,"NEW")

AAAA"'BBBB"'NEW"'C1C1C1]C2C2C2]C3C3C3"'DDDD

STRING FUNCTIONS 210 BASIC

CHAPTER. 10: :rtJBcrIOBS

PRINT INS$(B$,O,O,"NEW")

NEW~AAAA~BBBB~C1C1C1]C2C2C2]C3C3C3~DDDD

PRINT INS$(B$,3,1,"NEW")

AAAA~BBBB~C1C1Cl]NEW]C2C2C2]C3C3C3~DDDD

PRINT INS$(B$,3,-1,INEW")

AAAA~BBBB~EW]C1CIC1]C2C2C2]C3C3C3~DDDD

PRINT INS$(B$,7,2,"NEW")

AAAA~BBBB~C1C1C1]C2C2C2]C3C3C3~DDDD~~~~]]NEW

LEFT$(<string-exp>,<n~» Indicates a substring the first character through the value of the numeric expression. of the string expression from nth character where n is the

Example: PRINT LEFT$(A$,7)

ABCDEFG

LPAD$(<string-exp>,<n~» Adds leading spaces to a string. The two expressions are evaluated and the resulting string expression is expanded to the length indicated by the value of the numeric expression by adding sufficient leading spaces. If the string expression is already greater than or equal to the length indicated no spaces are added and the string is returned, unmodified.

Example: PRINT "1I";LPAD$("1234",6);"II"

II 123411

11123411

"1I";LPAD$("1234",3);"II"

LTREK$(<string-exp» Removes leading spaces from a string. The string expression is evaluated and any leading spaces are removed.

Example: PRINT LTRIM$("

ABC DEF II

ABC DEF ");"11"

HID$(<String-exp>,<n~I>,<n~2» Indicates a substring of the string expression starting with character N1, for N2 characters where

~1 and N2 are the values of the two numeric expressions. The length of the string returned will be at most N2-Nl+1 characters.

Example: PRINT MID$(A$,15,5)

OPQRS

OCTOF$«n~» The numeric expression is evaluated, integerized and translated into the string of characters representing the value of the number in octal. A six character string is always generated.

Example: PRINT OCTOF$(123);" ";OCTOF$(94)

000175 000156

BASIC 211 STRING FUBCTlOBS

BASIC REFERENCE HABUAL

OVR$(<String-expl>,<n~I>,<n~2>,<String-exp2» Truncates or expands the second string expression to exactly N2 characters, where N2 is the value of the second numeric expression. Then the first string expression is overlaid by the second string expression, from position N1 for N2 characters.

Example: PRINT OVR$(A$,2,3,"0123456")

A012EFGHIJKLMNOPQRSTUVWXYZ

REP$(<String-expl>,<n~I>,<n~2>,<String-exp2» This function is similar to the INS$ function except that it replaces a subfield instead of inserting the subfield. The substring <string-exp2> will replace the subfield designated by the values of the two numeric expressions. If there is no subfield to be replaced then the the substring will be inserted in its proper place. If the value of the second numeric expression is zero, the replacement is for the entire field designated by the first numeric expression.

If the first string expression does not have sufficient subfields, sufficient null fields will be added.

The string expression must not contain any characters whose value is greater than 127 or the results will be unpredicatable.

Using the character subfield delimiter: as the field delimiter and

Example: B$ = AAAA~BBBB~C1C1Cl]C2C2C2]C3C3C3~DDDD

PRINT REP$(B$,6,O,"HERE")

AAAA~BBBB~CICICl]C2C2C2]C3C3C3~DDDD~~HERE as the

PRINT REP$(B$,3,2,"NEW")

AAAA~BBBB~CICICl]NEW]C3C3C3~DDDD

PRINT REP$(B$,2,2,"NEW")

AAAA~BBBB]NEW~CICICl]C2C2C2]C3C3C3~DDDD

Note: Field and subfield delimiters cannot be created except with this function or the INS function. The field delimiters are not really the characters ~ and ] because the parity bit is turned on to indicate that the character is a delimiter and not a normal ASCII character.

RIGHT$(<string-exp>,<n~» Returns the substring of the string expression from the nth character through the last character in the string expression where n is the value of the numeric expression.

Example: PRINT RIGHT$(A$,20)

TUVWXYZ

RPAD$(<String-exp>,<n~» Adds trailing spaces to a string. The two expressions are evaluated and the resulting string expression is expanded to the length indicated by the value of the numeric expression by adding sufficient trailing spaces. If the string

STRIBG FUBCTIORS - 212 BASIC

CBAPTBR. 10: FOBCTIOIIS expression is indicated no unmodified. already greater spaces are added than and

'or equal to the length the string is returned,

Example: PRINT "1I"jRPAD$("1234",6)j"II"

111234 II

PRINT "1I"jRPAD$("1234",3)j"II"

11123411

RPT$(<n~>,<string-exp» Generates a string of <num-exp> repetitions of the

<string expression>.

Example: PRINT RPT$(3,"ABCD")

ABCDABCDABCD

RTRIK$(<string-exp» Removes trailing spaces from a string. The string expression is evaluated and any trailing spaces are removed.

Example: PRINT "II" jRTRIM$ ("

II ABC DEFII

ABC DEF

" ) j

"II"

SPACE$(<n~» Returns a string of spaces of <num-exp> length.

STR$(<n~»

Example: PRINT LEFT$(A$,3)&SPACE$(4)&MID$(A$,4,5)

ABC DEFGH

Indicates a string of numeric characters representing the value of the numeric expression. There are no leading or trailing blanks.

Example: PRINT "ABC";STR$(1.23)j"DEF"

ABC1.23DEF

PRINT "ABC"j1~23;"DEF"

ABC 1.23 DEF

Tnm$(<n~» Indicates a string of characters in normalized time format

(i.e., hh:mm:ss) representing the numeric expression interpreted as the number of seconds since midnight of the current day. The value 0 (zero) is interpreted as the current time of day.

Example: PRINT TIME$(7199),TIME$(0)

01:59:59 15:24:32

TRIK$(<string-exp» Removes any leading or trailing spaces and reduces all embedded multiple spaces to a single space.

Example: PRINT

IIABC

"II" jTRIM$ ("

DEF HIJII

ABC DEF HIJ " ) ; "II"

BASIC - 213 SDDTG FOBCTIOBS

BASIC REFERENCE HANUAL

10.4 Input/Output Functions

INP Returns the ASCII, integer value of the first character of the last input, if the first character was a control character or a user defined key. When the first character was not a control character, the value of the function is O. For example: if the last input was a CTRL/D the value of the INP is 4. If the last input was a CTRL/Z the value of INP is 26. If the last input was ABCDEFG the value of INP is O.

Also see the appendix on "User Definable Keys".

LINE (<num-exp»

PAGE (<num-exp»

POS (<num-exp»

Returns the integer value of the ATTACHed line length of device opened on the I/O channel whose value is <num-exp>. I/O channel o may be used to indicate the console device.

Example: PRINT LINE(O)

REM Console terminal

Returns the integer value of the ATTACHed page length of device opened on the I/O channel whose value is <num-exp>. I/O channel o may be used to indicate the console device.

Example: PRINT PAGE(O)

REM Console terminal

Returns the integer count of the number of characters output on the I/O channel indicated by the numeric expression.

Example: PRINT "123456";POS(O)

123456 6

I/O I1JBCTlOBS - 214 BASIC

CHAPTER. 10: I'DRCTIOBS

10.5 Log~cal Funct~ons

The following functions allow value (binary word--16 bits). value will be integerized. the programmer to manipulate the bits of an integer

All of the arguments are numeric expressions whose

LRL{<n~I>,<n~2» If the value for either of the expressions is negative then it is replaced with the value O. If the first exprression is greater than 65535 then it is replaced with the value O. If the second expression is greater than 15 then it is replaced with the value O. A logical rotate left is performed on the first integer for <num-exp2> bit positions.

LRR{<n~I>,<n~2» If the value for either of the expressions is negative then it is replaced with the value o.

If the first expression is greater than 65535 then it is replaced with the value O. If the second expression is greater than 15 then it is replaced with the value 9. A logical rotate right is performed on the value of <num-expl> for <num-exp2> bit positions.

LSL{<n~xpl>,<n~2» If the value for either of the expressions is negative then it is replaced with the value O. If the first expression is greater than 65535 then it is replaced with the value O. If the second expression is greater than 15 then it is replaced with the value 9. A logical shift left is performed on the value of <num-expl> for <num-exp2> bit positions.

LSR{<num-expI>,<n~2» If the value for either of the expressions is negative then it is replaced with the value O. If the first expression is greater than 65535 then it is replaced with the value O. If the second expression is greater than 15 then it is replaced with the value 9. A logical shift right is performed on the value of <num-expl> for <num-exp2> bit positions.

BASIC 215 LOGICAL FUBCTIOBS

BASIC 1lEFERERCE HARUAL

10.6 File Function

EOF ( <nUlll-elqJ> ) The numeric expression is evaluated and the I/O channel corresponding to that value is checked for end-of-file condition. If the channel has not reached end-of-file the value of the function is 0 (false). If the channel has reached end-of-file the value of the function is -1 (true).

Channel zero (console) is never at end-of-file and will cause an error if tested with this function. Use the INP function to test for a CTRL/Z.

FILE P'OBCTIOR - 216 BASIC

CHAPTER. 10: I'IJIICTlORS

10.1 Error Functions

The following two functions do not have any arguments and should only be used in an error handling routine (see ON ERROR and RESUME statments).

Returns the integer line number of the statement causing the error to occur. A value of zero is returned if no error has occured.

Note: When this function is used on the left side of a relational expression and an unsigned integer is used on the right side of the same relational expression the RENUMBER command will assume that the unsigned integer is a line number and adjust it accordingly.

Returns the integer error number of the error that occured. A value of zero is returned if no error has occured. For a list of error numbers, their meanings and what might cause them see the appendix "Error Messages".

This function may be assigned a value with the LET statement in order that error handling routines may be tested.

BASIC 211 ElUWR FDRCTIOBS

BASIC RD'ERERCE HARUAL

10.8 USR Function

The USR function allows the BASIC programmer to interface a assembler language subroutine to the BASIC language program.

When the user requires a procedure to be accomplished that requires real-time processing or can only be done with the features of the CPU that are not available to the BASIC program, he must write an assembler language program. In many cases it is advantageous to only have a part of the procedure written in assembler code with the more routine processes accomplished with a BASIC language program. In order to transfer control and data between the user written subroutine and the

BASIC program the USR function is used.

USR(<addr>,<n~»

USR(<addr>,<String-exp»

<addr> refers to the entry point address, relative to the load address of the assembler subroutine.

<num-exp> when evaluated and rounded to the nearest integer, is the sixteen bits of signed ~nteger data to be transmitted to the assembler subroutine via the HL registers. When the subroutine is ready to return control back to BASIC the numeric value to be assigned to the function should be placed in the HL register pair.

<string-exp> when evaluated, is left in the "string accumulator". The address of this string accumulator is placed in the HL register pair before control is given to the user subroutine. The string accumulator is a 256 byte area that contains a one byte length followed by up to 255 characters. This area may be used by the subroutine as long as care is taken not to exceed the 256 byte limit. When the subroutine is ready to return control back to

BASIC, it should load the HL register pair with the address of the string that is to be returned.

The USR function is a standard function call and may be used in any position of a

BASIC statement that the other functions may be used.

Only one user written assembler language subroutine may be in memory while BASIC is executing, however the one subroutine may in fact be several subroutines concatenated together. Information may be found regarding assembly language programming in the OASIS MACRO Assembler Language Reference Manual.

The subroutine is loaded into memory by specifying i t in an OPTION USR statement.

The OASIS MACRO Assembler Language Reference Manual has an example of a USR routine. un

I'DRCTIOR - 218 BASIC

APPENDIX A

RESERVKD WORDS

The following words are reserved and may not be used for variable names. The notation [ ••• l means that a variable may not even start with the word indicated, if that variable is ever used with an implied LET statement.

===================================================================================

ABS

AND

ASC

ATN

BIN

BINOF

CASE

CEND

CHAIN

CHR

CLEAR

COMMON

COS

CRT

CSI

DATA

DATE

DAY

DEF

DEL

DELETE

DIM

DTE

ELSE

END

EOF

EQV

ERL

ERR

EXP

EXT

FIX

FLOAT

FNEND

FN [ ••• 1

FOR

FORMAT

GET

GOSUB

GOTO

HEX

HEXOF

IFEND

IMP

INP

INPUT

INS

INT

LEFT

LEN

LET

LINE

LINK

LINPUT

LOG

LPAD

LRL

LRR

LSL

LSR

LTRIM

HAT

MATCH

MAX

MID

MIN

MOD

MOUNT

NBR

OCT

OCTOF

OPEN

OPTION

OTHERWISE

OUTPUT

OVR

PAGE

POS

PROMPT

PUT

QUIT

QUOTE

RANDOMIZE

READ

READNEXT

REM

REM [ ••• 1

REP

RESTORE

RESUME

RETURN

RIGHT

RND

ROUND

RPAD

RPT

RTRIM

RUN

SCH

SEC

SELECT

SGN

SIN

SLEEP

SPACE

SQR

STEP

STOP

STR

TAN

THEN

TIME

TRIM

UNLOCK

USR

VAL

WAIT

WEND

WHILE

WRITE

XOR

===================================================================================

All "variables" that start with the letters FN will always be treated as a reference to a user defined function. (See DEF statement.)

BASIC - 219 RESERVED WRDS

APPENDIX B

USER. DEFINABLE KEYS

OASIS BASIC allows the programmer to code programs in such a manner that he can test whether certain keys were entered and then take whatever action he has programmed. These certain keys are the control keys, usually refered to by CTRL/x where x is one of the standard alphabetic keys modified by the control key.

When a program asks for keyboard input (MAT INPUT, INPUT, LINPUT, or LINPUT USING,) and the operator responds with a control key, program control will return to the

BASIC program. The operator need not type a carriage return after the control key.

No characters will be displayed on the console device when the operator types a control key.

The program can test which control key, if any, was entered by using the INP function. Only input f.rom the console keyboard (I/O channel 0) may be tested with the INP function. The programmer may specify whatever action he wishes when the correct control key is entered.

This can be a very useful feature if the programmer is consistent in defining the meanings of the control keys. For instance he may define the CTRL/D to mean the current date. This is obviously easier for the operator to enter than typing the current date. It is also safer than programming a carriage return only to mean the current date or some other default value.

Some terminals have additional keys available to the operator. These are generally called function or program keys. If these keys generate an 8 bit code that is not one of the displayable ASCII characters then these keys may also be used as user definable keys by BASIC. The displayable ASCII characters have decimal values between 32 and 127, inclusive. To determine the exact values generated by these keys refer to the operators or users manual for the specific terminal.

Example:

The following is a simple program that shows the user definable key feature of

OASIS BASIC.

10 OPTION PROMPT CHR$(O)

20 LOOP: PRINT "Please type a control key: If;

30 LINPUT USING "!",KEY$\PRINT

IF INP=O THEN IF KEY$<>"" THEN GOTO ERROR

PRINT "The key you typed has a value of";INP;

PRINT "and was the key "; CRR$ (INP+64)

70 GOTO LOOP

80 ERROR: PRINT "You don't follow directions very well."

90 GOTO LOOP

USER. DEFINABLE KEYS - 220 BASIC

APPENDIX B: USER DD'IRABLE KEYS

B.l Control Key Values

Key Value Key Value Key Value Key Value

===================================================================================

P 16

Q 17

R 18

X y

[ 27

\ 28

] 29

***

===================================================================================

These key values are used for editing by LINPUT USING, and/or INPUT statments.

This is the escape code. Because the system control keys are escape sequences entry of this key once is an indication to OASIS that the next character may be a system request. To get a value 27 passed to the INP function the operator must type this key twice. When this is done one escape character is passed to BASIC which, if it is the first character of an input field, will set the INP function to

27.

***

This value may also bew generated by some terminals by a CTRL/DEL or CTRL/RUB.

Some systems have other keys that may be tested by this function. If this situation is possible then you should use the above program to detect and determine the value of the specific keys.

It is possible that a particular system may have other or different keys that are trapped by the operating system and never passed to the BASIC program. It is also possible that some keys may generate different values than those listed here. Both of these situations are dependent upon the SET values for: RUB OUT , LEFT, RIGHT, UP,

DOWN, CANCEL and ESCAPE. For more information see the chapter "SET COMMAND" in the

OASIS System Reference Manual.

BASIC - 221 USER. DEFDiABLE IEYS

BASIC B.EFERENCE HANDA!.

USER. DEPD1ABLE KEYS - 222 BASIC

APPENDIX C

CmtHAND SDHHARY

===================================================================================

AUTO

AUTO [<start line>[,<increment value>]]

BOTTOM

BOTTOM

BREAK

BREAK [AT <line reference> [AFTER <count>]]

BREAK [ON <variable> [CHANGE] [AFTER <count>]]

BREAK [ON <variable> <relation> <value>]

CHANGE

CHANGE /from string/to string/ [<range>]

CONTINUE

CONTINUE

DELETE

DELETE [<range>]

DOWN

<line-feed>

HELP

INDENT

INDENT [<indent value>]

LENGTH

LENGTH

LIST

LIST [<range>]

LOAD

LOAD <program name> [<program type>]

LOCATE

LOCATE /<string>/ [<range>]

LPLIST

LK[n]LIST [<range>]

LPXREF

LP[n]XREF

MODIFY

MODIFY [<range>]

BASIC - 223 COHHABD SlJIIIWlY

BASIC 1lD'ERERCE HARUAL

NAME [<program name>[.<program type>[:<program disk>]]]

QUIT

BENUHBER.

QUIT

[<number>]

[<unquoted string>]

RENUMBER [<first> [<incr> [<start> [<end>]]]]

~~ [<program name>] [<starting line>]

SAVE

STEP

SAVE [<program name> [<program type> [<program disk>]]]

STEP [<count>]

TOP

TOP

TRACE

'XRACE

.'KRACE VARS

UNBREAK [AT <line reference>]

UNBREAK [ON <variable>]

URTRACE

U~TRACE

<up-arrow key>

VARS

VARS [<variable list>]

XREF

===================================================================================

COIDfAIID SUHHAIlY - 224 BASIC

APPDlDIX D

===================================================================================

CASE

[<line-no>] [<label>] CASE <expression>

CERD

[<line-no>] [<label>] CEND

CHAIR

[<line-no>] [<label>] CHAIN <string expression>[,<line-no>]

CLEAR.

[<line-no>] [<label>] CLEAR [<variable list>]

CLOSE

[<line-no>] [<label>] CLOSE II<channel>

COHHOB

[<line-no>] [<label>] COMMON <variable list>

CSI

[<line-no>] [<label>] CSI <string expression>

DATA

[<line-no>] [<label>] DATA <literal>[,<literal>] •••

I ' "

"-~/

DEI"

[<line-no>] [<label>] DEF FN<simple variable>[«arg list»] [= <expression>]

DELETE

[<line-no>] [<label>] DELETE #<channel>,<key>

DIH

[<line-no>] [<label>] DIM <simple var>«numeric expr>[,<numeric expr>]» •••

ELSE

[<line-no> ]

[ <line-no>]

ELSE

[<line-no>] [<label>] END

I'NEND

[<line-no>] [<label>] FNEND

FOR.

[<line-no>] [<label>]

FOR <num var>=<num exp> TO <num exp>[ STEP <num exp>]

FOR <var> = <literal list>

GET

[<line-no>] [<label>] GET <device> <numeric expr>,<variable list>

GOSUB

[<line-no>] [<label>]

GOSUB <line reference>

GO SUB <line reference>

BASIC - 225 S"lATDfEBT S1JHHAIlY

BASIC REFERENCE MANUAL

COTO

[<line-no>] [<label>] GOTO <line reference>

[<line-no>] [<label>] GO TO <line reference>

[<line-no>] [<label>] IF <relation> THEN <statement> [ELSE <statement>]

[<line-no>] [<label>] IF <relation> THEN <line-ref> [ELSE <line-ref>]

[<line-no>] [<label>] IF <reI>

IFEND

[<line-no>] [<label>] IFEND

INPUT

[<line-no>] [<label>] INPUT [<prompt expression>,]<variable list>

[<line-no>] [<label>] INPUT #<channel>:<variable list>

[<line-no>] [<label>] INPUT #<channel>,<key>:<variable list>

LET

[<line-no>] [<label>] [LET] <string variable>

[<line-no>] [<label>] [LET] <numeric var> =

= <string expression>

[<line-no>] [<label>] [LET] <string variable><substring>

[<line-no>] [<label>] [LET] <user defined function>

[<line-no>] [<label>] [LET] ERR = <numeric expression>

= <string expr>

= <expression>

LINK

[<line-no>] [<label>] LINK <string expression>[,<line-no>]

LINPUT

[<line-no>] [<label>] LINPUT [<prompt expression>,]<string variable>

[<line-no>] [<label>] LINPUT #<channel>:<string variable>

[<line-no>] [<label>] LINPUT #<channel>,<key>:<string variable>

[<line-no>] [<label>] LINPUT [<prompt expr>,]USING<string expr>,<string var>

HAT

[<line-no>] [<label>] MAT <array name> = <array name>

[<line-no>] [<label>] MAT <array name> = «expression»

HAT INPUT

[<line-no>] [<label>] MAT INPUT <array name>

[<line-no>] [<label>] MAT INPUT #<channel>: <array name>

[<line-no>] [<label>] MAT INPUT #<channel>,<key>: <array name>

HAT PRINT

[<line-no>] [<label>] MAT PRINT <array name list> <punct>

[<line-no>] [<label>] MAT PRINT #<channel>: <array name list> <punct>

[<line-no>] [<label>] MAT PRINT #<channel>,<key>: <array name list> <punct>

HAT READ

[<line-no>] [<label>] MAT READ <array name>

[<line-no>] [<label>] MAT READ #<channel>: <array name>

[<line-no>] [<label>] MAT READ #<channel>,<key>: <array name>

HAT WR.I.TE

[<line-no>] [<label>] MAT WRITE #<channel>: <array name>

[<line-no>] [<label>] MAT WRITE #<channel>,<key>: <array name>

STATEHERT S1JHHA1lY - 226 BASIC

APPENDIX D: STATEHERT SUHHAIlY

HOUNT

[<line-no>] [<label>] MOUNT <string expression>

<line-no> NEXT [<variable>]

ON ERROR

[<line-no>] [<label>] ON ERROR GOTO <line reference>

[<line-no>] [<label>] ON ERROR GO TO 0

[<line-no>] [<label>] ON <numeric expression> GOTO <line reference list>

[<line-no>] [<label>] ON <numeric expression> GOSUB <line reference list>

OPEN

[<line-no>] [<label>] OPEN #<channel>: <string expr>,<mode> <method>[<options>]

OPTION

[<line-no>] [<label>] OPTION <option lis t>

OTHERWISE

[<line-no>] [<label>] OTHERWISE

PRINT

[<line-no>] [<label>] PRINT [<expression list><punct>]

[<line-no>] [<label>] PRINT #<channel>[:<expression list><punct>]

[<line-no>] [<label>] PRINT #<channel>,<key>[:<expression list><punct>]

PRINT USING

[<line-no>] [<label>] PRINT USING <mask>,<expression list><punct>

[<line-no>] [<label>] PRINT USING #<channel>: <mask>,<expr list><punct>

[<line-no>] [<label>] PRINT USING #<channel>,<key>: <mask>,<expr list><punct>

PUT

[<line-no>] [<label>] PUT <device> <numeric expression>,<expression list>

QUIT

[ <line-no>] [<label>] QUIT [<expression>]

RANDOHIZE

[<line-no>] [<label>] RANDOMIZE

[<line-no>] [<label>] READ <variable list>

[<line-no>] [<label>] READ #<channel>: <variable list>

[<line-no>] [<label>] READ #<channel>,<key>: <variable list>

READNEXT

[<line-no>] [<label>] READNEXT #<channel>,<string key>: <variable list>

[<line-no>] [<label>] REM <any characters>

RESTORE

[<line-no>] [<label>] RESTORE [<line reference>]

BASIC 227 -

S"I.ATEHEIrr SUHHAIlY

BASIC JlEI'ERERCE JWmAL

IlESUHE

[<line-no>] [<label>] RESUME <line reference>

[<line-no>] [<label>] RESUME 0

JlETOD

[<line-no>] [<label>] RETURN [<line ref>]

RUB

[<line-no>] [<label>] RUN [<string expression>] [,<line number>]

SELECT

[<line-no>] [<label>] SELECT [<variable>]

SLEEP

[<line-no>] [<label>] SLEEP <numeric expression>

STOP

[<line-no>] [<label>] STOP [<expression>]

[<line-no> ]

THEN <statement>

THEN <line number>

WAIT

[<line-no>] [<label>] WAIT

[<line-no>] [<label>] WAIT DEVICE <numeric expression>

[<line-no>] [<label>] WAIT PORT <numeric expr>,<numeric expr>[,<numeric expr>]

[<line-no>] [<label>] WAIT MEMORY <numeric exp>,<numeric exp>[,<numeric exp>]

[<line-no>] [<label>] WEND

WHILE

[<line-no>] [<label>] WHILE <numeric expression>

WJl.ITE

[<line-no>] [<label>] WRITE #<channel>: <expression list>

[<line-no>] [<label>] WRITE #<channel>,<key>: <expression list>

===================================================================================

STATEMENT SUHHAB.Y - 228 BASIC

APPENDIX E

FUNCTION SUHHARY

In the following summary the arguments N, Nl, and N2 all represent numeric expressions; the arguments A$ and B$ all represent string expressions.

ABS(B) Returns the absolute value of N.

Returns the ASCII value of the first character in A$. ASC(A$)

AT$(Nl,N2) Returns the string of characters that, if printed, would position the cursor at Nl,N2. (Nl is horizontal, N2 is vertical.)

ATH(N)

BIN (A$)

BINOF$(N)

Returns the arctangent of N (N in radians).

Returns a decimal value for the binary A$.

Returns a string representing the binary value of N.

CHR$(N)

COS(N)

CRT$(A$)

DATE$(N)

ERL

EXP(N)

EXT $ (A$,RI,N2)

Returns the character having the ASCII value of N.

Returns the cosine of N (N in radians).

Performs non x/y console output control.

Internal date to external date.

DAY (A$) External date to internal date.

DKL$(A$,NI,N2,B$) Returns the string of A$ with field designated by Nl and N2 removed.

DTE$(A$)

EOF(R)

Test A$ for valid date. When valid converts to normalized format, else returns null string.

Returns End-of-File flag for I/O channel N.

Returns line number of statement causing error.

Returns number of error.

Returns the value of e~N.

Returns the substring ~f A$ for field Nl of A$ and subfield N2 of field Nl.

FIX(R)

FLOAT(R)

FOItHAT$(R,A$)

BEX(A$)

BEXOF$(R)

Returns the integerized value of N.

Converts integer N to floating point.

Formats N according to mask A$.

Returns a decimal value for the hexadecimal A$.

Returns a string representing the hexadecimal value of N.

BASIC - 229 FOBCTIOB SDIIHAIl.Y

BASIC :REFERENCE MANUAL

IRP

INT(R)

Returns the numeric value of the confrol character input to console.

INS$(A$,NI,R2,B$) Returns the string of A$ with string B$ inserted after the substring of A$ for field Nl of A$ and subfield N2 of field Nl.

Returns the greatest integer which is less than or equal to N.

LEFT $ (A$,N)

LER(A$)

LIBE(N)

Returns the substring of A$ from the first character to the Nth character.

Returns the length of string A$.

Returns line length of device opened on channel N.

LOG (B)

LPAD$(A$,R)

LRL(BI,R2)

LRR(Rl,N2)

LSL(Rl,B2)

LSR(BI,B2)

Returns the natural logarithm of N.

Adds leading spaces to A$ to make string of length N.

Logical rotate left Nl for N2 bit positions.

Logical rotate right N1 for N2 bit positions.

Logical shift left N1 for N2 bit positions.

Logical shift right N1 for N2 bit positions.

LTRIH$(A$)

MATCH(A$,B$)

HAX(BI,B2)

KID$ (A$,BI,B2)

Remove leading spaces from string A$.

Tests string A$ against mask B$; returns true/false (-1/0).

Returns the greater value of N1 and N2.

Returns the substring of A$ from the N1th character for N2 characters.

MIB(BI,N2)

MOD (BI,B2)

Returns the lessor value of N1 and N2.

Returns remainder of N1 divided by N2.

BBI.(A$) Test A$ for numerics. Returns 0 if any non-numeric characters in

A$, else returns -1.

Returns a decimal value for the octal A$. OCT (A$) ocml' $ (B) Returns a string representing the octal value of N.

OVR$(A$,RI,B2,B$) Returns A$ with B$ overlaid, starting at N1th character for N2 characters.

PAGE (B)

Returns page length of device opened on channel N.

Returns the constant value 3.141592653590.

POS(B) Returns the current character position of output channel N.

FOBcnOB SUHllAR.Y - 230BASIC

APPENDIX It: FDBCTIOR SlJIMA1l.Y

SEC (A$)

SGN(R)

SIN(R)

SPACE$(N)

SQR(N)

STR$(N)

TAN(N)

TIHE$(N)

TRIH$(A$)

USR(NI,N2)

REP$(A$,NI,N2,B$) Returns the string of A$ with string B$ replacing the substring of A$ for field N1 of A$ and subfield N2 of field N1.

RIGHT $ (A$,N)

RND

ROUND (NI ,N2)

Returns the substring of A$ from the Nth character to the end.

Returns a random number between 0 and 1, exclusive.

Rounds N1 to number of positions indicated by N2.

RPAD$(A$,N)

RPT$(NI,A$)

RTRDI$(A$)

SCH(NI,A$,B$)

Adds trailing spaces to A$ to make string of length N.

Returns the string of N1 repetitions of A$.

Removes trailing spaces from string A$.

Returns the character position of the string B$ within A$ with the search starting at character position N1.

USR$(N,A$)

VAL (A$)

External time to internal time.

Returns the algebraic sign of N (+ or -).

Returns the sine of N (N in radians).

Returns the string of N blanks.

Returns the square root of N.

Returns the string of characters representing the number N.

Returns the tangent of N (N in radians).

Internal time to external time.

Remove leading and trailing spaces from string A$.

Calls assembly subroutine at relative location N1, passing N2 to the routine.

Cals assembly subroutine at relative location N, passing A$ to the routine.

Returns the numeric value of A$.

BASIC - 231 FOJICTIOR SUHlWtY

BASIC RD'ERERCE HANUAL

FURCTIOB S1JHHAB.Y 232 -

BASIC

APPENDIX F

ERIlOR HESSAGES

F.l Co..and Errors

AUTO cannot replace or merge lines

Indicates that the AUTO command attempted to use a line number already in use or that there was a line whose line number was between the last auto line number and the next auto line number to be used.

Disk Full

Indicates that the disk used by the SAVE command is full. Remember that saving an existing file causes the previous version of the file to be renamed BACKUP.

Insufficient IleJmry

An attempt was made to add another line to the program in memory that could not fit into the available memory.

Invalid cOJlllllal1d syntax

Indicates that the command was recognized but a syntax error was detected.

Invalid Prograa Hame

An attempt was made to NAME, SAVE, LOAD, or COMPILE a program using an invalid name. The program name must be at least two characters in length and start with a letter.

Invalid Statement Humber

An attempt was made to enter or display a line with an invalid line number. Line numbers must be between 1 and 9999.

Renumber Range Error

Indicates that the command would cause program. line numbers lines to that would be generated by the RENUMBER change their relative location in the

String missing or invalid

Occurs on a CHANGE or LOCATE command when no previous CHANGE or LOCATE command has been executed and no valid string arguments were specified.

Unrecognized command

Indicates that the command name was abbreviated too much or misspelled to an extent that the command desired could not be discerned.

BASIC - 233 EJUlOR :MESSAGES

BASIC REFERERCE MARUAL

F.2 Edit Errors

Comma Required

Colon Required

End of Line Required

Equal Sign Required

ExpresSion Required

File Mark Required

Keyword M1ssing or mis-spelled

M1ssing Parenthesis

Numeric Expression Required

Numeric Variable Required

Statement Bumber Required

String Expression Required

String Variable Required

Terminating Quote Required

Too Many Subscripts

Unbalanced Parenthesis

Unrecognized Statement

F.3 Compi1e Errors

Undefined Line

The compiler detected a reference to a line number that was never used in the program. The reference will be adjusted to the first line number used that is greater than the line referenced.

Undefined Label

The compiler detected a reference to a line label that was never defined in the program. The reference will be adjusted to the first line number used in the program.

ERROR KESSAGES - 234 BASIC

APPENDIX F: ERIlOB. MESSAGES

F.4 Execution Errors

The following errors may occur during the execution of a program. They are all trappable by user written error routines unless stated otherwise. In general, the non-trappable errors indicate a programming logic error that could not be corrected at run time anyway.

1 ESC-C

Operator typed an ESC,C during execution of the program.

2 Divide by Zero

Occurs during expression analysis if an attempt is made to divide by zero.

3 Overflow

An integer expression resulted in a value outside the range -32767 to

+32767 or a floating point exprression resulted in a value outside the range of -lO~126 to +lO~126.

4 Underflow

A floating point expression resulted in a value outside the range of

-lO~-126 to +lO~-126.

5 Illegal Number

Occurs on input type statements or string to numeric conversion type functions when the string of characters contains characters that are not allowed in numeric fields.

6 SQR of Negative

7 LOG of Zero

8 LOG of Negative

9 Insufficient Memory (non-trappable)

Occurs during execution when a statement attempts to define additional working storage that exceeds the amount of memory available.

10 Line not Found (non-trappable)

Occurs on the statements: CHAIN, ELSE, GOSUB, GOTO, LINK, ON ERROR, ON,

RESTORE, RESUME, RETURN, RUN, or THEN when the line number specified is not used in the program.

11 Label not Found (non-trappable)

Occurs on the statements: ELSE, GOSUB, GOTO, ON ERROR, ON, RESUME, and

RETURN, when the line label specified is not defined in the program.

BASIC - 235 EllROB. HESSAGES

BASIC REI'EIlERCE HANUAL

12 Return StaCk Empty (non-trappable)

Occurs on the RETURN statement when there is no GOSUB in effect.

13 Vend without Whi1e (non-trappable)

Occurs on the WEND statement without a statement when there is no

WEND is okay because encountered.)

WHILE in effect. (A WHILE the end of the program is

14 Next without For (non-trappable)

Occurs on the NEXT statement without a encountered.) statement when

NEXT is okay there is because no FOR in effect. (A FOR the end of the program is

15 Insufficient Data

Occurs on the INPUT statement when multiple fields are to be input and fewer fields are actually entered.

16 Inva1id Fi1e Humber (non-trappable)

Can occur on any of the file I/O statements expression is less than 1 or greater than 16. the file functions. when the channel number

Can also occur on any of

17 Resume without Error (non-trappable)

Occurs on the RESUME statement when there is no error in effect.

18 Inva1id Address (non-trappable)

Can occur on any of the statements or functions that access memory when the address is out of range.

19 Inva1id Separator

Occurs on input statements.

20 ON Range Error

Occurs in the ON GOSUB or ON GOTO statement when the numeric expression is less than one or greater than the number of line references specified.

21 Cend without Se1ect (non-trappable)

Occurs on the CEND statement when there is no SELECT in effect. (A SELECT statement without a CEND is okay because the end of the program is encountered.)

22 Type Mismatch (non-trappable)

23 Inva1id Zero Dimension (non-trappable)

Occurs if an OPTION BASE 1 has been executed and a reference is made to

DROR MESSAGES - 236 ~IC

APPENDIX 1': ER1lOR. MESSAGES the zero subscript of an array.

24 Inconsistent Usage (non-trappab1e)

Occurs when a DIM or COMMON attempts to dimension a name as a varib1e already defined or after an array reference is made to the same name in a variable. array with the same is dimension and a

25 Subscript Range (non-trappab1e)

Occurs on any reference to a subscripted array less than or greater than the number of elements dimensioned in the array.

26 Inva1id Using (non-trappab1e)

Indicates that a expression field was string.

PRINT USING statement mask specified string when the was numeric or the mask specified numeric when the field

27 Fi1e is not Open

Occurs on an attempt to CLOSE an I/O channel that is not currently open.

28 Fi1e is Open

Occurs on an attempt to OPEN an I/O channel that is currently in use by another file.

29 Inva1id File Bame

Occurs on the OPEN, CHAIN, RUN, or LINK statement when the file or program name is invalid. File and program names must be at least two characters in length and start with a letter. Program file types must be BASIC or

BASICOBJ. Can also occur on the OPEN statement when the device name is mis-spelled.

30 File not Found

31 Disk Fu11

Indicates an attempt was made to add wasn't sufficient space available on more data to the disk when there the disk. Can only occur on sequential file format output.

32 Directory Fu11

33 Protected Fi1e

Indicates an attempt was made to OPEN a file that was read protected, or an attempt was made to re-create a file that was delete protected, or an attempt was made to output to a file that was write protected.

BASIC - 237 EJUlOR. MESSAGES

BASIC REP'ERDlCE lfARUAL

34 Invalid Key

Indicates that an input or output type statement used a key on a sequential format file or did not use the proper type of key for a direct or indexed format file.

3S Wrong Access

Occurs on input type statements when the file was opened'for output or on an output type statement when the file was opened for input.

36 Out of Data

Occurs on the READ statement when there are no more DATA elements in the program.

37 Option Must be First (non-trappable)

Occurs on the OPTION BASE statement when there are variables defined.

Should perform a CLEAR first.

38 80 USR Program (non-trappable)

Indicates a reference to a USR function when there is not a USR program loaded.

39 Invalid Drive Code (non-trappable)

Occurs on the MOUNT statement when the drive is invalid or not attached.

40 Program not Found (non-trappable)

Occurs on a CHAIN, LINK, or RUN statement if the specified program cannot be found.

41 Invalid File Format (non-trappable)

Occurs on any attempt to input from a file created prior to version 5.31

OASIS and not converted with the FILECONV program; using READ on a record that was output with a PRINT; or using INPUT on a record that was output with a WRITE.

42 FNEND without DEF (non-trappable)

Occurs when an FNEND statement is encountered outside of a user defined function definition.

43 DEl not found (non-trappable)

Occurs on any reference to a user defined function that is not defined in the current program.

ERROR MESSAGES - 238 BASIC

APPENDIX G

PROGRAM EXAMPLES

G.l Example One

-10 INPUT IIRadius of circlell,R

-20 PRINT IIDiameter =11; 2. *R

-30 PRINT IIArea =";PI*R ..... 2.

-40 PRINT IICircumference =1I;2.*PI*R

-50 END

-RUN

Radius of circle? 2.5

Diameter = 5

Area = 19.63495408493

Circumference = 15.70796326795

G.2 Example TWo - String Conversion

The following example illustrates a method of translating the individual characters of a string into the decimal equivalents.

-AUTO

100

-RUN

DIM X(3)

LET STRING$ = "CATII

X(O) = LEN(STRING$)

FOR 1% = 1 TO X(O)

X(I%) = ASC(MID$(STRING$,I%,l»

NEXT 1%

PRINT IISTRING$ = ";STRING$,"Length of STRING$ =";X(O)

PRINT X(0),X(1),X(2),X(3)

END

STRING$

CAT Length of STRING$

65 84

BASIC - 239 -

BASIC :REFKRKRCE MANUAL

G.3 Example Three - Sine Wave

This example will produce a sine wave on the console terminal.

10 MAGNITUDE%

20 MIDDLE%

= LINE(0)*3./8.

LINE(0)/2.

30 FREQUENCY

40 FOR J

= .175

= 0 TO 100 STEP FREQUENCY

50 SINE = INT(MAGNITUDE%*SIN(J))

60 PRINT SINE;TAB(MIDDLE%+SINE);"*"

70 NEXT

EXAHPLES - 240 BASIC

APPENDIX G: P1WGB.AH EXAIIPLES

G.4 Example Four B~ll of Materials

-AUTO

10 REM Accept Bill of Materials

20 PRINT "How many items";

30 INPUT ITEM.COUNT%

FOR 1% = 1 TO ITEM.COUNT%

INPUT Q(I%),P(I%)

60 NEXT

70 PRINT

80 REM Display Bill of Materials, extension, and total

90 PRINT "Item Quantity Price Amount"

100

11 0

120

130

140

150

MAS K 1 $ = " 1111"

& S P AC E $ ( 11 ) &"

1111111111"

& S PAC E $ (9 ) &" $ 111111 • 1111" &

&" $ II , 111111 .11

FOR 1% = 1 TO ITEM.COUNT%

PRINT USING MASKl$,I%,Q(I%),P(I%),Q(I%)*P(I%)

LET TOTAL = TOTAL+Q(I%)*P(I%)

160

170

180

190 END

200

-RUN

LET MASK2$ =" TOTAL "&SPACE$ (35) &" $11,111111.1111"

PRINT USING MASK2$,TOTAL

How many items? 5

? 2,750

? 25,23.50

? 10,85.35

? 145,.08

? 75,2.35

Item Quantity

TOTAL

145

Price

$750.00

$ 23.50

$ 85.35

$ 0.08

$ 2.35

Amount

$1,500.00

$ 587.50

$ 853.50

$ 11.60

$ 176.25

$3,128.85

BASIC 241 EXAHPLES

BASIC REFERERCE MANUAL

G.5 Examp1e Five

The following sample illustrates the use of three functions (INP, INS, REP) and uses a disk file.

-AUTO

10 OPEN Ill: rrNAME.DATA:A",OUTPUT SEQUENTIAL\REM Create file

20 PRINT CRT$(IIC II );

30 PRINT AT$(1,6); "Name";

\REM Clear screen

\REM Display all the input fields

40 PRINT AT$(1,7);"Address";

50 PRINT AT$(1,8);"City";

60 PRINT AT$(33,8);"State l l

;

70 PRINT AT$(53,8);"Zip";

80 PRINT AT$(1,9);"SSN";

90 OPTION PROMPT II:"

100 R$ = II"

110 PRINT AT$(5,6);

120 LINPUT USING II

130 IF INP

140 R$

= 26 THEN 999

= INS$(R$,O,O,A$)

150 PRINT AT$(8,7);

160 LINPUT USING II

170 R$ = INS$(R$,l,O,A$)

180 PRINT AT$(5,8);

190 LINPUT USING "

200 R$ = INS$(R$,2,0,A$)

210 PRINT AT$(38,8);

\REM Initialize record

\REM Position for first input field

II, A$

\REM Entry of CTRL/Z means end

\REM A$ is first field

\REM Position for second input field

II, A$

\REM A$ is second field

\REM Position for third field

I f ,

\REM A$ is third field

\REM Position for fourth field

220 LINPUT USING"

I f ,

230 R$ = INS$(R$,3,1,A$)

240 PRINT AT$(56,8);

250 LINPUT USING"

260 R$

I f ,

REP$(R$,3,3,A$)

270 PRINT AT$(4,9);

280 LINPUT USING "

290 R$ = REP$(R$,4,0,A$)

300 PRINT III :R$

310 GOTO 20

320 END

330

I f ,

\REM A$ is second subfield of third

\REM Position for fifth field

\REM A$ is subfield 3 of third

\REM Position for sixth field

\REM A$ is fourth field

\REM Create new record in file

\REM Start over field

Lines 20 through 80, when executed, will display the field names:

Name

Address

City

SSN

State Zip

EXAMPLES - 242 BASIC

APPENDIX G: PlWGRAH EXAHPLES

Lines 110 through 280, when executed, position the cursor after each field name and allow input. Each field input is saved in the string R$ with appropriate field delimiters. For instance:

Name: JOSEPH E. BROWN

Address: 1234 S.E. MAIN STREET

City: SAN FRANCISCO

SSN: 123-45-6789

State: CA Zip: 99999

The above entry will produce a record that looks like this:

JOSEPH E. BROWN~1234 S.E. MAIN STREET~SAN FRANCISCO]CA]99999~123-45-6789

The characters ~ and] are the field delimiters. They differ from the normal ASCII character by having the parity bit turned on.

BASIC - 243 EXAHPLES

BASIC REFERERCE HABUAL

G.6 Exa.p1e Six - Sequential Pile I/O

The following example illustrates file input and formatted output using the AT function.

-AUTO

10 OPEN Ill: "NAME.DATA",INPUT SEQUENTIAL

20 LOOP: PRINT CRT$("C");

30 1% = 0

INPUT: LINPUT Ill: A$

IF EOF(l) THEN GOTO EXIT

PRINT AT$(6,I%+3);EXT$(A$,1,0);

100

PRINT AT$(6,I%+4);EXT$(A$,2,0);

PRINT AT$(6,I%+5);EXT$(A$,3,1);\L = LEN(EXT$(A$,3,1»

PRINT AT$(8+L,I%+5);EXT$(A$,3,2);\L = L+LEN(EXT$(A$,3,2»

PRINT AT$(10+L,I%+5);EXT$(A$,3,3);

110

120

130

140

150 EXIT: END

PRINT AT$(6,I%+6);EXT$(A$,4,0);

1% = 1%+5 \ IF 1%+5 < 23 THEN GOTO INPUT

WAIT

GOTO LOOP

160

Assuming that the file "NAME" contains the record from Example 5 the display will be as follows:

JOSEPH E. BROWN

1234 S.E. MAIN STREET

SAN FRANCISCO CA 99999

123-45-6789

There will be four names per page with two blank lines separating each name from the next.

EXAMPLES - 244 BASIC

APPENDIX G: PIlOGllAH EXAMPLES

G. 7 Example Seven - Indexed File I/O - Sequential Access

The following example illustrates a simple sequential list to the primary printer of a name and address file, printing in label format.

The format of the file being read is: Key name, last name first, separated by a comma, space from first name; record = address, city, state, zip, etc.

-AUTO 1000

1000 OPEN Ill: "NAMES.ADDRESS", INPUT INDEXED

1010 OPEN 112: "PRINTER1", OUTPUT SEQUENTIAL, FORMAT

1020 READ: READNEXT 1I1,KEY$: ADDR$,CITY$,STATE$,ZIP$ \REM Get next record

1030

1040

1050

1060

1070

1080

1090

1100

1110

1120

1130

1140

IF EOF(l) THEN 1170

C=SCH(KEY$,l,", ")

IF NOT C THEN 1070

\REM At end?

\REM Find end of last name

\REM Not found - assume okay

KEY$=RIGHT$(KEY$,C+2)&LEFT$(KEY$,C-1) \REM Restructure name

PRINT 112: " ";KEY$ \REM Print the name

IF LEN(ADDR$)=O THEN 1100 \REM If no address skip

PRINT /12: " ";ADDR$

PRINT /12: " ";CITY$;" ";STATE$;" "; \REM Print city and state

IF LEN(ZIP$)=5 THEN 1130 \REM If zip full then skip

ZIP$=FORMAT$(ZIP$,"99999") \REM Format Zip

PRINT 112: ZIP$ \REM Print the zip code

IF LEN(ADDR$)=O THEN PRINT /12: " " \REM Account for lost line

1150

1160

PRINT /12: "-"

GO TO READ

1170 REM End of file - clean up

1180

1190 END

CLOSE III CLOSE 112 \QUIT

\REM Triple space for next ' label'

\REM Get another record

In addition to illustrating the primary use of the READNEXT statement the above program shows a method of formating a number with leading zeroes printing (see line

1120).

BASIC

245 -

BASIC REFERENCE HANDA!.

G.8 Example Eight -,Indexed File Create

The following example illustrates a method of creating a new indexed file from a

BASIC program when the programmer is unsure of the amount of contiguous disk space available. This routine allows the operator to specify the number of records desired in the file or allows the operator to specify that the file is to be allocated for the largest record count that will fit in the available space.

3770

3779

3780

3790

3800

3810

3820

3830

3840

3850

3855

3860

3870

3880

3890

3900

3550 Cl$=AT$(I,PAGE(O»&CRT$("EOS")

3552 C2$=AT$(I,PAGE(0»&CRT$("EOS")

3554 C5$=CHR$(7) REM Bell code

3560 REM Create new file

3561

3562

3563

REM SI = record length

REM S2 = file size in records

REM Keylen = 30

3564

3565

3566

3570

3580

3590

3600

3630

3640

3650

3660

3670

3680

3690

3700

3710

3720

3730

3740

3750

3760

REM S is number of bytes to be used for record+key+overhead storage

REM SO is number of bytes to be used for sequential record pointers

REM VI is number of contiguous bytes available on disk

OPTION CASE "U"

PRINT Cl$;"Please mount the disk to contain the file";F$

PRINT "in the appropriate drive (Y /N) ,? ";R V$="N"

SI=158 \ REM SI=RECLEN

LINPUT USING V$,V$

IF INP=17 OR INP=26 OR V$="" OR V$="N" THEN 3940

PRINT Cl$;"How many records do you wish allocated? If;

LINPUT USING" ",V$

IF V$="" THEN S2=999999 \ GOTO 3700

IF NBR(V$)=O THEN PRINT C5$; \ GOTO 3650 ELSE S2=VAL(V$)+3

IF S2<=0 THEN S2=999999

PRINT C2$;"What is the largest area on the disk?-

LINPUT USING" ",Vl$

S3=SI+32 \ REM KEYLEN=30, overhead=2, S3=KEYLEN+RECLEN+2

IF S2>Vl/S3 THEN S2=INT(Vl/S3) \ REM S2 must be realistic

IF MOD(S2,4)<>3 THEN S2=S2-1 \ GOTO 3760

If;

IF Vl$="" OR NBR(Vl$)=O THEN PRINT C5$; \ GOTO 3700

Vl=VAL(Vl$)*1024 \ REM Convert to bytes

IF S3*S2+S2*2>Vl THEN S2=S2-4 \ GOTO 3770\REM Make more realistic

REM Take into account the overhead of rounding up to nearest 1024

S=S2*S3 \ IF MOD(S,1024»0 THEN S=S+1024-MOD(S,1024)

SO=S2*2 \ IF MOD(SO,512»0 THEN SO=SO+512-MOD(SO,512)

IF S+SO>Vl THEN S2=S2-4 \ GOTO 3780\REM Make sure it will fit!

REM Make S2 a prime number

FOR I=S2 TO 3 STEP -4

FOR J=3 TO SQR(I) STEP 2

Jl=I/J

'IF INT(Jl)=Jl THEN 3870

GOTO 3880

S2=I

CLOSE #1

CSI "CREATE "&F$&" (IND KEY 30 REC "&STR(SI)&" FILE "&STR$(S2)

Note that line 3570 will force input to be upper case only. Line 3640 validates the yiN input--default to NO--and checks for exit (CTRL/Q or CTRL/Z indicate exit).

Lines 3680 and 3720 validate the input for a numeric value.

EXAMPLES - 246 BASIC

APPENDIX G: PllOGRAH EXAHPLES

Line 3750 forces S2 to be a value that is close to the value to be used. Line 3760 then forces S2 to be the next lowest value whose remainder is 3 when divided by 4

(a requirement for indexed file sizes). Line 3770 then forces S2 to be a value that would fit in the available space but does not take into account any rounding to the nearest 1K boundary. Lines 3780 through 3800 then adjust S2 to account for rounding, keeping modulo 4 of S2 = 3.

Lines 3810 through indexed file sizes).

3880 then force S2 to be a prime number (another requirement of

The STEP value of -4 keeps the modulo 4 of S2 = 3.

BASIC 247 EXAHPLES

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