Define computers? Why computer is known as data processing

Define computers? Why computer is known as data processing
Introduction to Computer Systems; Data representation: Number systems, character representation
codes, Binary, hex, octal codes and their inter conversions. Binary arithmetic, Floating point arithmetic,
signed and unsigned numbers IEEE standards, CPU organization, ALU, registers, memory, the idea of
program execution at micro level. Concept of computing, contemporary Operating Systems such as DOS,
Windows, UNIX etc. (only brief user level description). Introduction to organization and architecture of
mainframe, mini and micro systems.
Concept of flow chart and algorithm; Algorithms to programs: specification, top-down development and
stepwise refinement ,Introduction to the design and implementation of correct, efficient and
maintainable programs, structured Programming,,Use of high level programming language for the
systematic development of programs, programmability and programming languages, Object codes,
compilers. Introduction to the Editing tools such as vi or MS-VC editors.
(Possible Theoritical Questions and Answers From Unit 1 & 2)
Question No: (1) Define computers? Why computer is known as data processing system?
What are the basic operations of Computer?
Answer: Computer: A computer is a programmable machine or device that performs pre-defined
or programmed computations or controls operations that are expressible in numerical or logical
terms at high speed and with great accuracy.
Computer is a fast operating electronic device, which automatically accepts and store input data,
processes them and produces results under the direction of step by step program.
Any Process that uses a computer program will enter data and summarize, analyze or otherwise
convert data into usable information. The process may be automated and run on a computer.
It involves recording, analyzing, sorting, summarizing, calculating, disseminating and storing data. Thus
Computer is known as data processing system.
Its various operations are:
1) It accepts data or instructions by way of input.
2) It stores data.
3) It can process data as required by the user.
4) It gives results in the form of output.
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5) It controls all operations inside a computer.
Question No: (2). What is Data and Information? Give the applications of computer? What are
the characteristics of computers?
Answer: Data -Data is the fact or raw material for the information processing.
Information – The processed data is called information.
Applications of computer
· Word Processing
· Internet
· Desktop publishing
· Digital video or audio composition
· Mathematical Calculations
· Robotics
· Weather analysis
Characteristics of computers
· Speed
· Accuracy.
· Automation.
· Endurance.
· Versatility.
· Storage.
· Cost Reduction.
Question No: (3). How will you classify computer systems?
Answer: Based on physical size, performance and application areas, we can generally divide computers
into four major categories:
1. Micro computer
2. Mini Computer
3. Mainframe computer and
4. Super Computer
Personal computers/Micro computers: A small, relatively inexpensive computer designed for an
individual user. In price, personal computers range anywhere from a few hundred dollars to thousands
of dollars. All are based on the microprocessor technology that enables manufacturers to put an
entire CPU on one chip.
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· Businesses use personal computers forward processing, accounting, desktop publishing, and for
running spreadsheet and database management applications. At home, the most popular use for
personal computers is for playing games.
Mainframe computer
Mainframes arecomputers used mainly by large organizations for critical applications, typically
bulk data processing such as census, industry and consumer statistics, enterprise resource planning,
and financial processing.
The term probably had originated from the early mainframes, as they were housed in enormous,
room-sized metal boxes or frames.
Mini computers:
A mini computer is a multi-user or time-sharing system. It is used for medium scale data processing such
as Bank account processing, Payroll processing etc., Mini computer process greater storage capacity and
larger memories as compared to micro computer.
Super computer
The fastest type ofcomputer. Supercomputers are very expensive and are employed for
specializedapplications that require immense amounts of mathematical calculations.
For example, weather forecasting requires a supercomputer. Other uses of supercomputers
include animated graphics, fluid dynamic calculations, nuclear energy research, and petroleum
Question No: (4). Explain the fundamental units of a computer with a block diagram? Explain
the basic computer organization in detail?
Answer: A computer can process data, pictures, sound and graphics. They can solve highly
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Input Unit:
Computers need to receive data and instruction in order to solve any problem. Therefore we need to
input the data and instructions into the computers. The input unit consists of one or more input
devices. Keyboard is the one of the most commonly used input device. Other commonly used
input devices are the mouse, floppy disk drive, magnetic tape, etc. All the input devices perform
the following functions.
· Accept the data and instructions from the outside world.
· Convert it to a form that the computer can understand.
· Supply the converted data to the computer system for further processing.
e.g. Keyboard, Scanner, Mouse, Joystick, Mike etc
Storage Unit:
The storage unit of the computer holds data and instructions that are entered through the
input unit, before they are processed. It preserves the intermediate and final results before these
are sent to the output devices. It also saves the data for the later use.
Types of Storage Devices:
(A) Primary Storage:
1. Stores and provides very fast.
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2. This memory is generally used to hold the program being currently executed in the computer,
the data being received from the input unit, the intermediate and final results of the program.
3. The primary memory is temporary in nature. The data is lost, when the computer is switched
4. In order to store the data permanently, the data has to be transferred to the secondary
memory. The cost of the primary storage is more compared to the secondary storage.
e.g. RAM, ROM etc
(B) Secondary Storage:
1. It stores several programs, documents, data bases etc.
2. The programs that run on the computer are first transferred to the primary memory
before it is actually run.
3. Whenever the results are saved, again they get stored in the secondary memory.
4. The secondary memory is slower and cheaper than the primary memory. Some of the
commonly used secondary memory devices are Hard disk, CD, etc.,
Memory Size:
All digital computers use the binary system, i.e. 0’s and 1’s. Each character or a number
is represented by an 8 bit code. The set of 8 bits is called a byte. A Character occupies 1
byte space. A numeric occupies 2 byte space. Byte is the space occupied in the memory. The
size of the primary storage is specified in KB (Kilobytes) or MB (Megabyte). One KB is
equal to 1024 bytes and one MB is equal to 1000KB. The size of the primary storage in a typical PC
usually starts at 16MB. PCs having 32 MB, 48MB, 128 MB, 256MB memory are quite common.
Output Unit:
The output unit of a computer provides the information and results of a computation to outside world.
Printers, Visual Display Unit (VDU) are the commonly used output devices. Other commonly used output
devices are floppy disk drive, hard disk drive, and magnetic tape drive.
Arithmetic Logical Unit:
All calculations are performed in the Arithmetic Logic Unit (ALU) of the computer. It also does
comparison and takes decision. The ALU can perform basic operations such as addition,
subtraction, multiplication, division, etc and does logic operations viz, >, <, =, ‘etc. Whenever
calculations are required, the control unit transfers the data from storage unit to ALU once the
computations are done, the results are transferred to the storage unit by the control unit and then it is
send to the output unit for displaying results.
Control Unit:
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It controls all other units in the computer. The control unit instructs the input unit, where to store the
data after receiving it from the user. It controls the flow of data and instructions from the storage unit to
ALU. It also controls the flow of results from the ALU to the storage unit. The control unit is generally
referred as the central nervous system of the computer that control and synchronizes its working.
Central Processing Unit:
The control unit and ALU of the computer are together known as the Central Processing Unit (CPU). The
CPU is like brain performs the following functions:
• It performs all calculations.
• It takes all decisions.
• It controls all units of the computer.
A PC may have CPU-IC such as Intel 8088, 80286, 80386, 80486, Celeron, Pentium, Pentium Pro, Pentium
II, Pentium III, Pentium IV, Dual Core, and AMD etc.
Question No: (5). With suitable examples, explain about Number systems?
Answer: A number system is a set of rules and symbols used to represent a number. There are
several different number systems. Some examples of number systems are as follows:
· Binary (base 2)
· Octal (base 8)
· Decimal (base 10)
· Hexadecimal (base 16)
Decimal and Hexadecimal numbers can each be represented using binary values. This enables
decimal, hexadecimal, and other number systems to be represented on a computer which is based
around binary (0 or 1 / off or on). The base (or radix) of a number system is the number of units that is
equivalent to a single unit in the next higher counting space. In the decimal number system, the
symbols 0-9 are used in combination to represent a number of any sizes.
For example, the number 423 can be viewed as the following string of calculations:
(4 x 100) + (2 x 10) + (3 x 1) = 400 + 20 + 3 = 423
Question No: (6). Explain various generations of computers with features?
Answer: Generation of Computers:
Each phase of computer development is known as a separate generation of computers. The
computer can be classified into four generations according to their type of electronic circuits such
as vacuum tube, transistor, IC etc.
(a) The First Generation Computers (1949-55)
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Main Features:
1) The computers of this generation used vacuum tubes.
2) These computers used machine language for giving instructions.
3) They used the concept of stored program.
4) These computers were 5000 times faster than the MARK-I.
5) The first generation computers were welcomed by Government and Universities.
1)These computers were very big in size. The ENIAC machine was 30 x 50 feet in size and
30 tons in weight. So, these machines required very large space for their workings.
2)Their power consumption was very high.
3)These computers had slow operating speed and small computing capacity.
4)These computers had a very small memory.
(b) The Second Generation Computers (1956-65)
Main Features:
1) The computers of this generation replaced vacuum tubes with transistors.
2) Magnetic cores were invented for storage.
3) Different magnetic storage devices were developed in this generation.
4) Commercial applications were developed during this period. Eighty percent of these computers
were used in business and industries.
(c) Third Generation Computers (1966-75)
Main Features:
· The third generation computers replaced transistors with’ Integrated Circuits’. These Integrated
Circuits are also known as chips.
· The size of main memory was increased and reached about 4 megabytes.
· Magnetic disk technology had been improved and drive having capacity upto 100
MBPS came into existence.
· The CPU becomes more powerful with the capacity of carrying out 1 million instructions per
· This generation computers were relatively inexpensive and faster.
· The application area also increased in this generation. The computers were used in other areas like
education, small businesses survey, analysis along with their previous usage areas.
(d) The Fourth Generation Computers (1976-Present)
Main Features:
i.The fourth generation computers replaced small scale integrated circuits and medium scale
integrated circuits with the microprocessors chip.
ii. Semiconductor memories replaced magnetic core memories.
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iii. The hard-disks are available of the sizes upto 200 GB. The RAID technology (Redundant Array
of Inexpensive Disks) gives storage upto thousands of GB.
iv. Computer cost came down rapidly in this generation.
v. Application of computers is increased in various areas like visualization, parallel computing,
multimedia etc.
(e) The Fifth Generation Computers
Mankind along with the advancement in science and technology is working hard to bring the Vth
Generation of computer. These computers will have the capability of thinking on their own like
an man with the help of Artificial Intelligence (AI). the 21st century will be better, faster, smaller
and smarter computers.
Question No: (6). Explain the classification of computers?
Personal Computers:
A personal computer (PC) is a self-contained computer capable of input, processing, output, and
storage. A personal computer is designed to be a single-user computer and must have at least one input
device, one output device, a processor, and memory. The three major groups of PCs are desktop
computers, portable computers, and handheld computers. Desktop Computers: A desktop computer is
a PC designed to allow the system unit, input devices, output devices, and other connected
devices to fit on top of, beside, or under a user’s desk or table. This type of computer may be used in the
home, a home office, a library, or a corporate setting.
Portable Computers:
A portable computer is a PC small enough to be moved around easily. As the name suggests, a laptop
computer fits comfortably on the lap. As laptop computers have decreased in size, this type of
computer is now more commonly referred to as a notebook computer. Manufacturers recently
began introducing a new type of computer called the tablet PC, which has a liquid crystal display
(LCD) screen on which the user can write using a special-purpose pen, or stylus. Tablet PCs rely on
digital ink technology that allows the user to write on the screen. Another type of portable
computer, called a wearable computer, is worn somewhere on the body, thereby providing a user with
access to mobile computing capabilities and information via the Internet.
Handheld Computers:
An even smaller type of personal computer that can fit into the hand is known as a handheld computer
(also called simply handheld, pocket PC, or Palmtop). In recent years, a type of handheld
computer called a personal digital assistant (PDA) has become widely used for performing
calculations, keeping track of schedules, making appointments, and writing memos. Some
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handheld computers are Internet-enabled, meaning they can access the Internet without wire
connections. For example, a smart phone is a cell phone that connects to the Internet to allow
users to transmit and receive e-mail messages, send text messages and pictures, and browse through
Web sites on the phone display screen.
A workstation is a high-performance single-user computer with advanced input, output, and storage
components that can be networked with other workstations and larger computers. Workstations
are typically used for complex applications that require considerable computing power and highquality graphics resolution, such as computer-aided design (CAD), computer-assisted manufacturing
(CAM), desktop publishing, and software development.
Midrange Servers/Minicomputers:
Linked computers and terminals are typically connected to a larger and more powerful computer
called a network server, sometimes referred to as a host computer. Although the size and
capacity of network servers vary considerably, most are midrange rather than large mainframe
(i) Midrange server – formerly known as a minicomputer, a midrange server is a powerful
computer capable of accommodating hundreds of client computers or terminals (users) at the
same time.
(ii) Terminal – a device consisting of only a monitor and keyboard, with no processing
capability of its own.
Mainframe Computers:
Larger, more powerful, and more expensive than midrange servers, a mainframe computer is capable of
accommodating hundreds of network users performing different computing tasks. These computers
are useful for dealing with large, ever-changing collections of data that can be accessed by many users
simultaneously. Government agencies, banks, universities, and insurance companies use mainframes to
handle millions of transactions each day.
A supercomputer is the fastest, most powerful, and most expensive of all computers. Many are
capable of performing trillions of calculations in a single second. Primary applications include
weather forecasting, comparing DNA sequences, creating artificially intelligent robots, and
performing financial analyses.
Question No: (7). Explain Second Memory in detail?
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Answer: Secondary storage devices, as indicated by the name, save data after it has been saved by the
primary storage device, usually referred to as RAM (Random Access Memory). From the moment
we start typing a letter in Microsoft Word, for example, and until we click on "Save," your entire
work is stored in RAM. However, once you power off your machine, that work is completely
erased, and the only copy remaining is on the secondary storage device where we saved it, such
as internal or external hard disk drive, optical drives for CDs or DVDs, or USB flash drive.
Internal Hard Disk Drive
The internal hard disk drive is the main secondary storage device that stores all of your data
magnetically, including operating system files and folders, documents, music and video. The
hard disk drive is a stack of disks mounted one on top of the other and placed in a sturdy case. They are
spinning at high speeds to provide easy and fast access to stored data anywhere on a disk.
External Hard Disk Drive
External hard disk drives are used when the internal drive does not have any free space and you need to
store more data. In addition, it is recommended to always back up all of our data and an external hard
drive can be very useful, as they can safely store large amounts of information. They can be connected
by either USB connection to a computer and can even be connected with each other in case you need
several additional hard drives at the same time.
Optical Drive
An optical drive uses lasers to store and read data on CDs and DVDs. It basically burns a series
of bumps and dips on a disc, which are associated with ones and zeros. Then, this same drive
can interpret the series of ones and zeros into data that can be displayed on your monitors. There are a
few different types of both CD and DVD disks, but the main two types include R and RW, which stand for
Recordable (but you can write information on it just once) and Rewritable (meaning you can record data
on it over and over again).
USB Flash Drive
USB flash memory storage device is also portable and can be carried around on a key chain. This type of
a secondary storage device has become incredibly popular due to the very small size of device compared
to the amount of data it can store (in most cases, more than CDs or DVDs). Data can be easily read using
the USB (Universal Serial Bus) interface that now comes standard
with most of the computers.
Question No: (8). Explain about memory in Computer System?(or) Write short notes on
memory of a computer?
Answer: The Role of Memory: The term "memory" applies to any electronic component capable of
temporarily storing data.
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There are two main categories of memories:
Internal memory that temporarily memorizes data while programs are running. Internal memory uses
micro conductors, i.e. fast specialized electronic circuits. Internal memory corresponds to what we
call random access memory (RAM).
Auxiliary memory (also called physical memory or external memory) that stores information over
the long term, including after the computer is turned off. Auxiliary memory corresponds to magnetic
storage devices such as the hard drive, optical storage devices such as CD-ROMs and DVD-ROMs, as well
as read-only memories.
Technical Characteristics
(a) Capacity, representing the global volume of information (in bits) that the memory can
(b) Access time, corresponding to the time interval between the read/write request and the
availability of the data
(c) Cycle time, representing the minimum time interval between two successive accesses
(d) Throughput, which defines the volume of information exchanged per unit of time,
expressed in bits per second
(e) Non-volatility, which characterizes the ability of a memory to store data when it is not
being supplied with electricity
The ideal memory has a large capacity with restricted access time and cycle time, a high
throughput and is non-volatile. However, fast memories are also the most expensive. This is why
memories that use different technologies are used in a computer, interfaced with each other and
organized hierarchically. The fastest memories are located in small numbers close to the
processor. Auxiliary memories, which are not as fast, are used to store information permanently.
Types of Memories
Random Access Memory
Random access memory, generally called RAM is the system's main memory, i.e. it is a space
that allows you to temporarily store data when a program is running. Unlike data storage on an
auxiliary memory such as a hard drive, RAM is volatile, meaning that it only stores data as long
as it supplied with electricity. Thus, each time the computer is turned off, all the data in the memory
are irremediably erased.
Read-Only Memory
Read-only memory, called ROM, is a type of memory that allows you to keep the information
contained on it even when the memory is no longer receiving electricity. Basically, this type of
memory only has read-only access. However, it is possible to save information in some types of
ROM memory.
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Flash Memory
Flash memory is a compromise between RAM-type memories and ROM memories. Flash memory
possesses the non-volatility of ROM memories while providing both read and writes access However,
the access times of flash memories are longer than the access times of RAM.
Question No: (9). Elaborate the various Peripheral (Input and Output) Devices?
Answer: Input/Output devices are required for users to communicate with the computer. In simple
terms, input devices bring information INTO the computer and output devices bring information
OUT of a computer system. These input/output devices are also known as peripherals since they
surround the CPU and memory of a computer system. Some commonly used Input/Output devices are
listed in table below.
It is a text base input device that allows the user to input alphabets, numbers and other characters. It
consists of a set of keys mounted on a board.
Alphanumeric Keypad: It consists of keys for English alphabets, 0 to 9 numbers, and special characters
like + − / * ( ) etc.
Function Keys: There are twelve function keys labeled F1, F2, F3… F12. The functions assigned to these
keys differ from one software package to another. These keys are also user programmable keys.
Special-function Keys
These keys have special functions assigned to them and can be used only for those specific purposes.
Functions of some of the important keys are defined below.
Enter-It is similar to the ‘return’ key of the typewriter and is used to execute a command or program.
Spacebar-It is used to enter a space at the current cursor location.
Backspace-This key is used to move the cursor one position to the left and also delete the
character in that position.
Delete-It is used to delete the character at the cursor position.
Insert-Insert key is used to toggle between insert and overwrite mode during data entry.
Shift-This key is used to type capital letters when pressed along with an alphabet key. Also used to type
the special characters located on the upper-side of a key that has two characters defined on the
same key.
Caps Lock-Cap Lock is used to toggle between the capital lock features. When ‘on’, it locks the
alphanumeric keypad for capital letters input only.
Tab-Tab is used to move the cursor to the next tab position defined in the document. Also,it is used to
insert indentation into a document.
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Ctrl-Control key is used in conjunction with other keys to provide additional functionality on the
Alt-Also like the control key, Alt key is always used in combination with other keys to perform
specific tasks.
Esc-This key is usually used to negate a command. Also used to cancel or abort executing programs.
Numeric Keypad
Numeric keypad is located on the right side of the keyboard and consists of keys having
numbers (0 to 9) and mathematical operators (+ − * /) defined on them. This keypad is provided
to support quick entry for numeric data.
Cursor Movement Keys
These are arrow keys and are used to move the cursor in the direction indicated by the arrow (up, down,
left, right).
(b) Mouse
The mouse is a small device used to point to a particular place on the screen and select in order
to perform one or more actions. It can be used to select menu commands, size windows, start programs
etc. The most conventional kind of mouse has two buttons on top: the left one being used most
Mouse Actions
Left Click :Used to select an item.
Double Click : Used to start a program or open a file.
Right Click : Usually used to display a set of commands.
Drag and Drop : It allows you to select and move an item from one location to another. To achieve this
place the cursor over an item on the screen, click the left
mouse button and while holding the button down move the cursor to where you want to
place the item, and then release it.
(c) Joystick
The joystick is a vertical stick which moves the graphic cursor in a direction the stick is moved. It
typically has a button on top that is used to select the option pointed by the cursor. Joystick is used as
an input device primarily used with video games, training simulators and controlling robots
Scanner is an input device used for direct data entry from the source document into the computer
system. It converts the document image into digital form so that it can be fed into the computer.
Capturing information like this reduces the possibility of errors typically experienced during large
data entry. Hand-held scanners are commonly seen in big stores to scan codes and price information for
each of the items. They are also termed the bar code readers.
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(e) Bar code Reader: A bar code is a set of lines of different thicknesses that represent a
number. Bar Code Readers are used to input data from bar codes. Most products in shops have
bar codes on them. Bar code readers work by shining a beam of light on the lines that make up the bar
code and detecting the amount of light that is reflected back
(f) Light Pen: It is a pen shaped device used to select objects on a display screen. It is quite like the
mouse (in its functionality) but uses a light pen to move the pointer and select any object on the screen
by pointing to the object. Users of Computer Aided Design (CAD) applications commonly use the
light pens to directly draw on screen.
(g) Touch Screen: It allows the user to operate/make selections by simply touching the display screen.
Common examples of touch screen include information kiosks, and bank ATMs.
(h)Digital camera: A digital camera can store many more pictures than an ordinary camera. Pictures
taken using a digital camera are stored inside its memory and can be transferred to a computer
by connecting the camera to it. A digital camera takes pictures by converting the light passing
through the lens at the front into a digital image.
(i) The Speech Input Device
The “Microphones - Speech Recognition” is a speech Input device. To operate it we require using a
microphone to talk to the computer. Also we need to add a sound card to the computer. The Sound
card digitizes audio input into 0/1s .A speech recognition program can process the input and
convert it into machine-recognized commands or input.
Output Devices
(a) Monitor
Monitor is an output device that resembles the television screen and uses a Cathode Ray Tube (CRT) to
display information. The monitor is associated with a keyboard for manual input of characters and
displays the information as it is keyed in. It also displays the program or application output. Like the
television, monitors are also available in different sizes.
(b) Liquid Crystal Display (LCD)
LCD was introduced in the 1970s and is now applied to display terminals also. Its advantages like
low energy consumption, smaller and lighter have paved its way for usage in portable computers
(c) Printer
Printers are used to produce paper (commonly known as hardcopy) output. Based on the technology
used, they can be classified as Impact or Non-impact printers. Impact printers use the typewriting
printing mechanism wherein a hammer strikes the paper through a ribbon in order to produce
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output. Dot-matrix and Character printers fall under this category. Non-impact printers do not touch
the paper while printing. They use chemical, heat or electrical signals to etch the symbols on paper.
Inkjet, Deskjet, Laser, Thermal printers fall under this category of printers. When we talk about printers
we refer to two basic qualities associated with printers: resolution, and speed. Print resolution is
measured in terms of number of dots per inch (dpi). Print speed is measured in terms of number of
characters printed in a unit of time and is represented as characters-per-second (cps), lines-perminute (lpm), or pages-per-minute (ppm).
(d) Plotter
Plotters are used to print graphical
makes line drawings on paper using
graphs, drawings, charts, maps etc.
(Computer Aided Design) and CAM
output on paper. It interprets computer commands and
multicolored automated pens. It is capable of producing
Computer Aided Engineering (CAE) applications like CAD
(Computer Aided Manufacturing) are typical usage areas for
(e) Audio Output: Sound Cards and Speakers:
The Audio output is the ability of the computer to output sound. Two components are needed:
Sound card – Plays contents of digitized recordings, Speakers – Attached to sound card.
Question No(10):Define Software & Hardware? What is an instruction? What are registers?
Answer: (10): Software:- Computer instructions or data, anything that can be stored electronically is
software. Computer software or just software is a general term used to describe the role that
computer programs, procedures and documentation in a computer system.
Hardware - (computer science) the mechanical, magnetic, electronic, and electrical components
making up a computer systemhardware. Hardware includes not only the computer proper but also the
cables, connectors, power supply units, and peripheral devices such as the keyboard, mouse, audio
speakers, and printers.
Instruction: An instruction is a basiccommand. The term instruction is often used to describe the
most rudimentaryprogramming commands. For example, a computer'sinstruction set is the
list of all the basic commands in the computer's machine language.
Register: A special, high-speed storage area within the CPU. All data must be represented in a
register before it can be processed. For example, if two numbers are to be multiplied, both
numbers must be in registers, and the result is also placed in a register.
Question No:- (9): Give the categories of Software with example?
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(A).Application Software:
Application Software is a set of programs for a specific application. Application software is useful for
word processing, accounting, and producing statistical report, Graphics, Excel and Data Base.
Programming languages COBOL, FORTRAN, C++,VB, VC, Java
Types of Application Software
Application software enables users to perform the activities and work that computers were designed
for. The specific type of application used depends on the intended purpose, and there are application
programs for almost every need.
(a) Individual application software refers to programs individuals use at work or at home. Examples
include word processing, spreadsheet, database management, and desktop publishing programs.
(b) Collaboration software (also called groupware) enables people at separate PC workstations to
work together on a single document or project, such as designing a new automobile engine.
(c) Vertical application software is a complete package of programs that work together to perform core
business functions for a large organization. For example, a bank might have a mainframe computer at
its corporate headquarters connected to conventional terminals in branch offices, where they are
used by managers, tellers, loan officers, and other employees. All financial transactions are fed to the
central computer for processing. The system then generates managers’ reports, account statements,
and other essential documents.
Other Application Software Models
Shareware: Shareware is software developed by an individual or software publisher who retains
ownership of the product and makes it available for a small “contribution” fee. The voluntary fee
normally entitles users to receive online or written product documentation and technical help.
Freeware: Freeware is software that is provided free of charge to anyone wanting to use it. Hundreds
of freeware programs are available, many written by college students and professors who create
programs as class projects or as part of their research.
Open Source Software: An open source software program is software whose programming code is
owned by the original developer but made available free to the general public, who is encouraged to
experiment with the software, make improvements, and share the improvements with the user
Question No (10): What do you understand by the compiler? What are various phases of compiler?
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Answer: Compiler: A compiler is a computer program (or set of programs) that transforms source
code written in a programming language (the source language) into another computer language (the
target language, often having a binary form known as object code).
Various Phases of Compiler: Following are various phases of Compiler:
A common division into phases is described below. In some compilers, the ordering of phases may differ
slightly, some phases may be combined or split into several phases or some extra phases may be
inserted between those mentioned below.
Lexical analysis This is the initial part of reading and analysing the program text: The text is read and
divided into tokens, each of which corresponds to a symbol in the programming language, e.g., a
variable name, keyword or number.
Syntax analysis This phase takes the list of tokens produced by the lexical analysis and arranges these in
a tree-structure (called the syntax tree) that reflects the structure of the program. This phase is often
called parsing.
Type checking This phase analyses the syntax tree to determine if the program violates certain
consistency requirements, e.g., if a variable is used but not declared or if it is used in a context that does
not make sense given the type of the variable, such as trying to use a boolean value as a function
Intermediate code generation The program is translated to a simple machine independent intermediate
Register allocation The symbolic variable names used in the intermediate code are translated to
numbers, each of which corresponds to a register in the target machine code.
Machine code generation The intermediate language is translated to assembly language (a textual
representation of machine code) for a specific machine architecture.
Assembly and linking- The assembly-language code is translated into binary representation and
addresses of variables, functions, etc., are determined.
The first three phases are collectively called the frontend of the compiler and the last three phases are
collectively called the backend. The middle part of the compiler is in this context only the intermediate
code generation, but this often includes various optimizations and transformations on the intermediate
Each phase, through checking and transformation, establishes stronger invariants on the things it passes
on to the next, so that writing each subsequent phase is easier than if these have to take all the
preceding into account. For example, the type checker can assume absence of syntax errors and the
code generation can assume absence of type errors. Assembly and linking are typically done by
programs supplied by the machine or operating system vendor,
Question No (11): Explain working of Loader, Linker, Interpreter and Assembler?
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Answer: Loader: In a computer operating system, a loader is a component that locates a given program
(which can be an application or, in some cases, part of the operating system itself) in offline storage
(such as a hard disk), loads it into main storage (in a personal computer, it's called random access
memory), and gives that program control of the computer (allows it to execute its instruction s).
A program that is loaded may itself contain components that are not initially loaded into main storage,
but can be loaded if and when their logic is needed. In a multitasking operating system, a program that
is sometimes called a dispatcher juggles the computer processor's time among different tasks and
calls the loader when a program associated with a task is not already in main storage.
Linker: Also called link editor and binder, a linker is a program tha t combines object modules to form
an executable program. Many programming languages allow you to write different pieces of code,
called modules, separately. This simplifies the programming task because you can break a large program
into small, more manageable pieces. Eventually, though, you need to put all the modules together. This
is the job of the linker. In addition to combining modules, a linker also replaces symbolic addresses with
real addresses. Therefore, you may need to link a program even if it contains only one module.
The linkage editor accepts two major types of input:
• Primary input, consisting of object decks and linkage editor control statements.
• Additional user-specified input, which can contain both object decks and control
statements, or load modules. This input is either specified by you as input, or is incorporated
automatically by the linkage editor from a call library.
Output of the linkage editor is of two types:
• A load module placed in a library (a partitioned data set) as a named member
• Diagnostic output produced as a sequential data set.
• The loader prepares the executable program in storage and passes control to it directly.
Interpreter: An interpreter normally means a computer program that executes, i.e. performs,
instructions written in a programming language. An interpreter may be a program that either
• executes the source code directly
• translates source code into some efficient intermediate representation (code) and
immediately executes this
• explicitly executes stored precompiled code made by a compiler which is part of the
interpreter system
Assembler: An assembler translates an assembly language source program into machine codes.
Though the assembly language is the symbolic representation of machine codes, a computer
cannot understand it. After translating the assembly language program into machine codes by the
assembler, the program becomes ready for the execution.
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Question No (12): Explain in detail the steps involved in Software Development Process?
Answer: Software development life cycle model is also called as waterfall model which is followed by
majority of systems.
This software development life cycle process has the following seven stages in it namely
1. System Requirements Analysis
2. Feasibility study
3. Systems Analysis and Design
4. Code Generation
5. Testing
6. Maintenance
7. Implementation
1. System Requirements Analysis:
The first essential or vital thing required for any software development is system. Also the system
requirement may vary based on the software product that is going to get developed. So a careful
analysis has to be made about the system requirement needed for the development of the product.
After the analysis and design of the system requirement phase the system required for the development
would be complete and the concentration can be on the software development process.
2. Feasibility study:
After making an analysis in the system requirement the next step is to make analysis of the
software requirement. In other words feasibility study is also called as software requirement analysis.
In this phase development team has to make communication with customers and make analysis of
their requirement and analyze the system. By making analysis this way it would be possible to
make a report of identified area of problem. By making a detailed analysis on this area a
detailed document or report is prepared in this phase which has details like project plan or schedule of
the project, the cost estimated for developing and executing the system, target dates for each phase of
delivery of system developed and so on. This phase is the base of software development process
since further steps taken in software development life cycle would be based on the analysis
made on this phase and so careful analysis has to be made in this phase.
3. Systems Analysis and Design:
This is an important phase in system development .Here analysis is made on the design of the system
that is going to be developed. In other words database design, the design of the architecture chosen,
functional specification design, low level design documents, high level design documents and so on
takes place. Care must be taken to prepare these design documents because the next phases
namely the development phase is based on these design documents. If a well structured and analyzed
design document is prepared it would reduce the time taken in the coming steps namely
development and testing phases of the software development life cycle.
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4. Code Generation:
This is the phase where actual development of the system takes place. That is based on the design
documents prepared in the earlier phase code is written in the programming technology chosen. After
the code is developed generation of code also takes place in this phase. In other words the code is
converted into executables in this phase after code generation.
5. Testing:
A software or system which is not tested would be of poor quality. This is because this is the
phase where system developed would be tested and reports are prepared about bugs or errors in
system. To do this testing phase there are different levels and methods of testing like unit testing,
system test and so on. Based on the need the testing methods are chosen and reports are prepared
about bugs. After this process the system again goes to development phase for correction of errors and
again tested. This process continues until the system is found to be error free. To ease the testing
process debuggers or testing tools are also available.
To develop reliable and good quality Program/Software we need to follow the
following 5 steps :
1. Requirement Specification.
2. Analysis.
3. Design.
4. Implementation.
5. Verification and testing.
Question No (13): Explain the steps involved in developing a program? (or) Brief
about planning the computer program?
Answer: The Programming Process – Purpose
1. Understand the problem
• Read the problem statement
• Question users
• Inputs required
• Outputs required
• Special formulas
• Talk to users
2. Plan the logic
(a) Visual Design Tools
• Input record chart
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• Printer spacing chart
• Hierarchy chart
• Flowchart
(b) Verbal Design Tools
• Narrative Description
• Pseudocode
3. Code the program
• Select an appropriate programming language
• Convert flowchart and/or Pseudocode instructions into programming language statements
4. Test the program
1. Syntax errors
2. Runtime errors
3. Logic errors
4. Test Data Set
5. Implement the program
• Buy hardware
• Publish software
• Train users
6. Maintain the program
• Maintenance programmers
• Legacy systems
• Up to 85% of IT department budget
Question No (14): Explain flowchart in detail?
Answer:A flowchart is a schematic representation of an algorithm or a stepwise process, showing the
steps as boxes of various kinds, and their order by connecting these with arrows. Flowcharts are used in
designing or documenting a process or program.
A flow chart, or flow diagram, is a graphical representation of a process or system that details the
sequencing of steps required to create output. A flowchart is a picture of the separate steps of a process
in sequential order.
The benefits of flowcharts are as follows:
a. Communication: Flowcharts are better way of communicating the logic of a system to all concerned.
b. Effective analysis: With the help of flowchart, problem can be analyzed in more effective way.
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c. Proper documentation: Program flowcharts serve as a good program documentation, which is
needed for various purposes.
d. Efficient Coding: The flowcharts act as a guide or blueprint during the systems analysis and program
development phase.
e. Proper Debugging: The flowchart helps in debugging process.
f. Efficient Program Maintenance: The maintenance of operating program becomes easy with the help
of flowchart. It helps the programmer to put efforts more efficiently on that part.
• Logic Flowcharts are easy to understand. They provide a graphical representation of actions to be
• Logic Flowcharts are well suited for representing logic where there is intermingling among many
• Logic Flowcharts may encourage the use of GoTo statements leading to software design that is
unstructured with logic that is difficult to decipher.
• Without an automated tool, it is time-consuming to maintain Logic Flowcharts.
• Logic Flowcharts may be used during detailed logic design to specify a module.
• However, the presence of decision boxes may encourage the use of GoTo statements, resulting in
software that is not structured. For this reason, Logic Flowcharts may be better used during Structural
Complex logic: Sometimes, the program logic is quite complicated. In that case, flowchart becomes
complex and clumsy.
Alterations and Modifications:If alterations are required the flowchart may require re-drawing
Reproduction:As the flowchart symbols cannot be typed, reproduction of flowchart becomes a
The essentials of what is done can easily be lost in the technical details of how it is done.
a. In drawing a proper flowchart, all necessary requirements should be listed out in logical order.
b. The flowchart should be clear, neat and easy to follow. There should not be any room for ambiguity in
understanding the flowchart.
c. The usual direction of the flow of a procedure or system is from left to right or top to
d. Only one flow line should come out from a process symbol.
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e. Only one flow line should enter a decision symbol, but two or three flow lines, one for
each possible answer, should leave the decision symbol.
f. Only one flow line is used in conjunction with terminal symbol.
g. Write within standard symbols briefly. As necessary, you can use the annotation symbol to
describe data or computational steps more clearly.
h. If the flowchart becomes complex, it is better to use connector symbols to reduce the
number of flow lines. Avoid the intersection of flow lines if you want to make it more
effective and better way of communication.
i. Ensure that the flowchart has a logical start and finish.
j. It is useful to test the validity of the flowchart by passing through it with a simple test data.
Question No (15): Describe in detail about algorithm? Give example
Answer: An algorithm is a description of a procedure which terminates with a result. Simple algorithms
can be implemented within a function.
Properties of an algorithm
• No ambiguity
• There should not be any uncertainty about which instruction to execute next.
• The algorithm should conclude after a finite number of steps.
• The algorithm should be general.
• Biggest among two numbers
• Addition of N numbers
• Finding Factorial of a number
• Finding Fibonacci series.
• Statements should be in simple English
• Must produce a solution for the specified problem
• It should be concise
• Each instruction should be written in separate line and express one action.
• Capitalize keywords such as READ, PRINT and so on.
• Instruction should be written from top to bottom, with one entry and one exit.
• Should allow easy transition from design to coding in programming language.
• Language Independent.
• Easy to develop a program from pseudo code than flowchart.
• Easy to translate into programming language.
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• It is compact.
• No visual representation of program logic
• No accepted standards for writing pseudo codes.
• Cannot be compiled or executed.
• No real form or syntax rules.
• Finding a number is prime or not
Question No(16): Define Operating System? What are functions and typesof operating System?
Answer: OPERATING SYSTEM: Operating System is a software that can be defined as:
• An interface between users and hardware - an environment "architecture”
• Allows convenient usage; hides the tedious stuff
• Allows efficient usage; parallel activity, avoids wasted cycles
• Provides information protection
• Gives each user a slice of the resources
• Acts as a control program.
Functions of operating System:
An operting system manages hardware, runs applications, provides an interface for users, and
stores, retrieves, and manipulates files.
It manages the hardware and software resources of the system.
It provides a stable, consistent way for applications to deal with the hardware without having to
know all the details of the hardware.
System tool (programs) used to monitor computer performance,debug,problems, or maintain
parts of the system.
A set of libraries or functions which may use to perform specific tasks especially relating to
interfacing with computer system components.
It avoids the situation of deadlock.
It is responsible for resource and performance optimization.
It manages process management and memory management
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Question No(17): What are various Internal and External DOS Commands?
Answer: Internal Commands: The internal commands reside in COMMAND.COM, which loads into
memory when the computer system is started; these commands do not reside on disk. e.g.
TIME- Displays current time and allows it to be changed.
Syntax: TIME
DATE- Displays current date and allows it to be changed.
Syntax: DATE
CLS- Clears the screen.
Syntax: CLS
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DIR- Shows directory information of a diskette: name, size, and the date and time stamp of
Syntax: DIR [d:][path]
Optional switches:
/p Display dir info and pauses display when the screen is full
/w Display names and extensions only in five columns
To display a file directory listing for D:\LET\ANNUAL
(from D:\LET\ANNUAL)
(from D:\DATA)
COPY- Copies a file. Name of copy may be the same as original, or different.
Syntax: COPY [d:][path][name.ext] [d:][path][name.ext]
Optional switches:
/v Verify, copies the file and compares it with the original
/b Binary file
To copy a file from D:\BATCH to the root of A: drive
(from A: drive)
(from D:\BATCH)
To copy a file from the root of C: to A: drive and change its name
C:\>COPY MSDOS.SYS A:\MSDOSSYS.BAK (from the root of C:)
To copy all of the files from the root of A: to D:\CCV\ENGCOMP
(from A:)
TYPE-Displays the contents of a file.
Syntax: TYPE [d:][path][name.ext]
To display the contents of the file MY.LET to the screen
DEL- Deletes a file from disk.
Syntax: DEL [d:][path][name.ext]
To delete one file:
To del all files in current directory
A:\>DEL *.*
REN- Renames a file.
Syntax: REN [d:][path][name.ext] [d:][path][newname.ext]
To change the name of the file D:\LET\ANNUAL\99.DOC to 1999.DOC
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(from D:\LET)
(from D:\DATA)
MD- Makes (creates) a new directory.
Syntax: MD [d:][path][dirname]
To create a directory named HERMIT in the root of D: drive
(from D:\)
(from C:\)
RD- Removes an existing directory
Syntax: RD [d:][path][dirname]
To remove the HERMIT sub-directory
(from D:\)
(from C:\)
CD- Changes the current directory.
Syntax: CD [path][dirname]
To make D:\HERMIT the current directory
(from D:\)
(from D:\DATA)
(directory must be empty).
PATH-The PATH command is used to help the command interpreter find external commands
which are not in the current directory. The command interpretter looks into the DOS
environment for "PATH=" and then searches the paths (each separated from the next by a
semicolon) that follow.
Syntax: PATH=[path;path;...]
To set the DOS PATH:
To display the current path:
SET PROMPT- Used to specify the appearance of the DOS prompt.
(from the command line)
(in a batch file)
To display current drive & current path followed by ">" as prompt
To display the current date, time, and drive on separate lines
To redefine F9 to CD\Windows\Start Menu\Programs\Startup
SET PROMPT $e[0,67;"'CD\Windows\Start Menu\Programs\Startup'";13p
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External Commands:-The external commands are files that do reside on disk and have an extension of
.COM, .EXE, or .BAT. Both command types are executed from the MS-DOS prompt. Instructions for
external commands are disk-based. This means the file with the name of the command must be loaded
into RAM at the moment when the command is given. Application programs are external commands
and some DOS programs are external. The syntax for some of the more useful DOS external commands,
including their parameters and switches follow:
(a) FORMAT -Prepares a diskette for use by DOS.
Syntax: FORMAT [d:]
Parameters: [d:] = Drive which is to receive the format.
Optional switches:
/s Include all system files necessary to make disk "bootable"
/b Reserve space for system files on diskette. (Formats 320k instead of 360k).
/v Volume label of 11 characters
Some examples:
• To format a diskette in drive B: without system files: FORMAT B:
• To format a diskette in drive A: with system files: FORMAT A: /s
• To give the formatted diskette a volume name, include the /v switch: FORMAT A: /V
Combine switches to format a boot diskette with a volume label:FORMAT A: /S /V
(b) CHKDSK -Analyzes disk or diskette (first and only parameter) and displays disk and memory
status report.
Syntax: CHKDSK [d:] [/f] [/v]
Parameters: [d:] = Drive upon which to perform the checkdisk.
Optional switches:
/f Fix. Writes lost clusters to a disk file and corrects file allocation table.
/v Verbose. Lists all files on a disk.
• To display statistics about the diskette in drive A: CHKSDK A:
To display statistics about the first hard disk and fix any lost clusters: CHKSDK A: /f
(c) DISKCOPY-Makes an exact copy of a diskette, including hidden system files if they are present.
Syntax: DISKCOPY [d1:] [d2:]
Parameters:[d1:] = Drive for source diskette, [d2:] = Drive for target diskette.
Example: To make an exact copy of a diskette in drive A: to a diskette in B:DISKCOPY A: B:
To make an exact copy of a diskette using only drive A: DISKCOPY A: A:
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DISKCOPY asks for a SOURCE diskette (the diskette being copied) and a TARGET diskette (the diskette
being copied to). The TARGET diskette need not be formatted, DOS will format it while doing the
DISKCOPY. If the SOURCE diskette is bootable, the system will be transferred to the TARGET as well. The
two disk drives must always use the same media.
Question No:(19): Explain Architecture of Unix? What are various Unix Commands?
Answer:- UNIXS is named after UNICS (UNiplexed Information and Computing Service). Its architecture
can be shown as below:
(1)UNIX Shell- Shell is an ordinary user program – needs the ability to read from and write to the
terminal, and execute other programs, Commands may take arguments, which are passed to the
called program as character strings
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Shell does not have to open terminal, but it has access automatically to a file ‘standard input’
(for reading), file ‘standard output’ (for writing normal output), and file ‘standard error’ (for
writing error messages)
Shell can redirect standard input/output to files
It can also use Pipe symbol
Example: grep ter *.t | sort >out
Possible pipeline – sequence of pipe symbols
Single user can run several programs at once
Shell syntax for running a program in the background – use &
Example: wc –l <a >b &
Shell scripts refers to the files containing shell command
UNIX Utility Programs- refers to standard application available with UNIX.
Large number of utility programs
Divided into six categories
File and directory manipulation commands
Example: cp a b | ls *.*
Example: grep (extracts lines containing patterns), cut, paste,
Program development tools such as editors/compilers
Example: cc (C compiler), make (maintain large programs whose source code
consists of multiple files)
Text processing
Example: vi
System administration
Example: mount (mount file system)
Example: kill 1325 (kill a process), chmod (change privileges of a file)
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UNIX Kernel- is the heart of the operating system with following structure:
All UNIX drivers are classified as either character device drivers (mouse, keyboard) or block
device drivers (disk)
Network device drivers (possible character devices, but handled very differently)
Process dispatching – when interrupt happens, context switch happens between processes
Editors such as vi/emacs need raw tty
Shell is line oriented, hence uses cooked mode and line disciplines
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Networking software is layered with MAC/Routing/Transport layers and Socket interface
On top of buffer cache sits file system
Most UNIX systems support multiple file systems
Berkeley fast file system
Log-structured file system
Various System V file systems
On top of file system comes file naming, directory management, hard link and symbolic link
management, etc
On top page cache sits virtual memory (VM)
All paging logic is here, such as replacement algorithm
On top of VM is mapping files onto VM and high level page fault management code
Figure out what to do when a page fault occurs
On top of process dispatching is process management
Process scheduler to choose which process to run next
If threads are managed in the kernel, thread management is also here
Note in some UNIX systems, threads are managed in user space
On top of scheduling we have signal processing and process creation and termination
Top layer has the system call interface
All system calls are directed to one of the lower modules, depending on the nature of
the call
Top layer also has entrance to interrupts and traps Entrance to signals, page faults,
processor exceptions of all kinds, I/O interrupts
Various Commands Of Unix:Directories:File and directory paths in UNIX use the forward slash "/"
to separate directory names in a path.
"root" directory
directory usr (sub-directory of / "root" directory)
/usr/STRIM100 STRIM100 is a subdirectory of /usr
Moving around the file system:
Show the "present working directory", or current directory.
Change current directory to your HOME directory.
cd .. Change current directory to the parent directory of the current directory.
cd $STRMWORK: Change current directory to the directory defined by the environment variable
cd ~bob:Change the current directory to the user bob's home directory (if you have permission).
Listing directory contents:
list a directory
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ls -l list a directory in long ( detailed ) format
for example:
$ ls -l
drwxr-xr-x 4 cliff user
1024 Jun 18 09:40 WAITRON_EARNINGS
-rw-r--r-- 1 cliff user 767392 Jun 6 14:28 scanlib.tar.gz
^^ ^ ^ ^ ^
^ ^ ^ ^
|| | | | |
| | | |
| | | | | owner group
size date time name
| | | | number of links to file or directory contents
| | | permissions for world
| | permissions for members of group
| permissions for owner of file: r = read, w = write, x = execute -=no permission
type of file: - = normal file, d=directory, l = symbolic link, and others...
ls -a
List the current directory including hidden files. Hidden files start
with "."
ls -ld * List all the file and directory names in the current directory using long format. Without the "d"
option, ls would list the contents
of any sub-directory of the current. With the "d" option, ls
just lists them like regular files.
Changing file permissions and attributes
chmod 755 file
Changes the permissions of file to be rwx for the owner, and rx for the group and the
world. (7 = rwx = 111 binary. 5 = r-x = 101 binary)
chgrp user file Makes file belong to the group user.
chown cliff file Makes cliff the owner of file.
chown -R cliff dir Makes cliff the owner of dir and everything in its directory tree.
You must be the owner of the file/directory or be root before you can do any of these things.
Moving, renaming, and copying files:
cp file1 file2
copy a file
mv file1 newname
move or rename a file
mv file1 ~/AAA/
move file1 into sub-directory AAA in your home directory.
rm file1 [file2 ...] remove or delete a file
rm -r dir1 [dir2...] recursively remove a directory and its contents BE CAREFUL!
mkdir dir1 [dir2...] create directories
mkdir -p dirpath
create the directory dirpath, including all implied directories in the path.
rmdir dir1 [dir2...] remove an empty directory
Viewing and editing files:
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cat filename Dump a file to the screen in ascii.
more filename Progressively dump a file to the screen: ENTER = one line down
SPACEBAR = page down q=quit
less filename Like more, but you can use Page-Up too. Not on all systems.
vi filename
Edit a file using the vi editor. All UNIX systems will have
head filename Show the first few lines of a file.
head -n filename Show the first n lines of a file.
tail filename Show the last few lines of a file.
tail -n filename Show the last n lines of a file.
Shells :The behavior of the command line interface will differ slightly depending on the shell program
that is being used.Depending on the shell used, some extra behaviors can be quite nifty.You can find out
what shell you are using by the command:
echo $SHELL
Of course you can create a file with a list of shell commands and execute it like a program to perform a
task. This is called a shell script. This is in fact the primary purpose of most shells, not the interactive
command line behavior.
Environment variables
You can teach your shell to remember things for later using environment variables.For example under
the bash shell:
export CASROOT=/usr/local/CAS3.0 Defines the variable CASROOT with the value
export LD_LIBRARY_PATH=$CASROOT/Linux/lib Defines the variable LD_LIBRARY_PATH with the
value of CASROOT with /Linux/lib appended,
or /usr/local/CAS3.0/Linux/lib
By prefixing $ to the variable name, you can evaluate it in any command:
Changes your present working directory to the value of CASROOT
Prints out the value of CASROOT, or /usr/local/CAS3.0
printenv CASROOT Does the same thing in bash and some other shells.
Interactive History: A feature of bash and tcsh (and sometimes others) you can use the up-arrow keys to
access your previous commands, edit
them, and re-execute them.
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grep string filename > newfile
Redirects the output of the above grep
command to a file 'newfile'.
grep string filename >> existfile
Appends the output of the grep command to the end of 'existfile'.
The redirection directives, > and >> can be used on the output of most commands to direct their output
to a file.
The pipe symbol "|" is used to direct the output of one command to the input
of another.
For example:
ls -l | more This commands takes the output of the long format directory list command
"ls -l" and pipes it through the more command (also known as a filter).
In this case a very long list of files can be viewed a page at a time.
du -sc * | sort -n | tail
The command "du -sc" lists the sizes of all files and directories in the
current working directory. That is piped through "sort -n" which orders the
output from smallest to largest size. Finally, that output is piped through "tail"
which displays only the last few (which just happen to be the largest) results.
Command Substitution
You can use the output of one command as an input to another command in another way called
command substitution. Command substitution is invoked when by enclosing the substituted command
in backwards single quotes. For example:
cat `find . -name aaa.txt`
which will cat ( dump to the screen ) all the files named aaa.txt that exist in the current directory or in
any subdirectory tree.
Searching for strings in files: The grep command
grep string filename prints all the lines in a file that contain the string
Searching for files : The find command
find search_path -name filename
find . -name aaa.txt Finds all the files named aaa.txt in the current directory or
any subdirectory tree.
find / -name vimrc Find all the files named 'vimrc' anywhere on the system.
find /usr/local/games -name "*xpilot*"
Find all files whose names contain the string 'xpilot' which
exist within the '/usr/local/games' directory tree.
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Reading and writing tapes, backups, and archives: The tar command
The tar command stands for "tape archive". It is the "standard" way to read
and write archives (collections of files and whole directory trees).
Often you will find archives of stuff with names like stuff.tar, or stuff.tar.gz. This
is stuff in a tar archive, and stuff in a tar archive which has been compressed using the
gzip compression program respectivly.
Chances are that if someone gives you a tape written on a UNIX system, it will be in tar format,
and you will use tar (and your tape drive) to read it.
Likewise, if you want to write a tape to give to someone else, you should probably use
tar as well.
Tar examples:
tar xv
Extracts (x) files from the default tape drive while listing (v = verbose)
the file names to the screen.
tar tv Lists the files from the default tape device without extracting them.
tar cv file1 file2
Write files 'file1' and 'file2' to the default tape device.
tar cvf archive.tar file1 [file2...]
Create a tar archive as a file "archive.tar" containing file1,
tar xvf archive.tar extract from the archive file
tar cvfz archive.tar.gz dname
Create a gzip compressed tar archive containing everything in the directory
'dname'. This does not work with all versions of tar.
tar xvfz archive.tar.gz
Extract a gzip compressed tar archive. Does not work with all versions of tar.
tar cvfI archive.tar.bz2 dname
Create a bz2 compressed tar archive. Does not work with all versions of tar
File compression: compress, gzip, and bzip2
The standard UNIX compression commands are compress and uncompress. Compressed files have
a suffix .Z added to their name. For example:
compress part.igs Creates a compressed file part.igs.Z
uncompress part.igs Uncompresseis part.igs from the compressed file part.igs.Z.
is not required.
Note the .Z
Another common compression utility is gzip (and gunzip). These are the GNU compress and
uncompress utilities. gzip usually gives better compression than standard compress,
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but may not be installed on all systems. The suffix for gzipped files is .gz
gzip part.igs Creates a compressed file part.igs.gz
gunzip part.igs Extracts the original file from part.igs.gz
The bzip2 utility has (in general) even better compression than gzip, but at the cost of longer
times to compress and uncompress the files. It is not as common a utility as gzip, but is
becoming more generally available.
bzip2 part.igs
Create a compressed Iges file part.igs.bz2
bunzip2 part.igs.bz2 Uncompress the compressed iges file.
Looking for help: The man and apropos commands
Most of the commands have a manual page which give sometimes useful, often more or less detailed,
sometimes cryptic and unfathomable discriptions of their usage. Some say they
are called man pages because they are only for real men.
man ls Shows the manual page for the ls command
You can search through the man pages using apropos
apropos build
Shows a list of all the man pages whose discriptions contain the word "build"
Do a man apropos for detailed help on apropos.
Basics of the vi editor
Opening a file
vi filename
Creating text
Edit modes: These keys enter editing modes and type in the text
of your document.
i Insert before current cursor position
I Insert at beginning of current line
a Insert (append) after current cursor position
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A Append to end of line
r Replace 1 character
R Replace mode
<ESC> Terminate insertion or overwrite mode
Deletion of text
x Delete single character
dd Delete current line and put in buffer
ndd Delete n lines (n is a number) and put them in buffer
J Attaches the next line to the end of the current line (deletes carriage return).
Undo last command
cut and paste
yy Yank current line into buffer
nyy Yank n lines into buffer
p Put the contents of the buffer after the current line
P Put the contents of the buffer before the current line
cursor positioning
^d Page down
^u Page up
:n Position cursor at line n
:$ Position cursor at end of file
^g Display current line number
h,j,k,l Left,Down,Up, and Right respectivly. Your arrow keys should also work if
if your keyboard mappings are anywhere near sane.
string substitution
Substitute string2 for string1 on lines
n1 to n2. If g is included (meaning global),
all instances of string1 on each line
are substituted. If g is not included,
only the first instance per matching line is
^ matches start of line
. matches any single character
$ matches end of line
These and other "special characters" (like the forward slash) can be "escaped" with \
i.e to match the string "/usr/STRIM100/SOFT" say "\/usr\/STRIM100\/SOFT"
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Substitute 'cat' for 'dog', every instance
for the entire file - lines 1 to $ (end of file)
Substitute 'bird' for 'frog' on lines
23 through 25. Only the first instance
on each line is substituted.
Saving and quitting and other "ex" commands
These commands are all prefixed by pressing colon (:) and then entered in the lower
left corner of the window. They are called "ex" commands because they are commands
of the ex text editor - the precursor line editor to the screen editor
vi. You cannot enter an "ex" command when you are in an edit mode (typing text onto the screen)
Press <ESC> to exit from an editing mode.
Write the current file.
:w new.file
Write the file to the name 'new.file'.
:w! existing.file Overwrite an existing file with the file currently being edited.
Write the file and quit.
Quit with no changes.
:e filename
Open the file 'filename' for editing.
:set number
Turns on line numbering
:set nonumber Turns off line numbering
Question No:(20) What are the characteristics of structure programming?
Answer:-Structured programming (sometimes known as modular programming) is a subset of
procedural programming that enforces a logical structure on the program being written to make it more
efficient and easier to understand and modify.
Certain languages such as Ada, Pascal, and dBASE are designed with features that encourage or enforce
a logical program structure.
Structured programming frequently employs a top-down design model, in which developers map out
the overall program structure into separate subsections. A defined function or set of similar functions is
coded in a separate module or submodule, which means that code can be loaded into memory
more efficiently and that modules can be reused in other programs. After a module has been tested
individually, it is then integrated with other modules into the overall program structure.
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Program flow follows a simple hierarchical model that employs looping constructs such as "for,"
"repeat," and "while." Use of the "Go To" statement is discouraged.
Structured programming was first suggested by Corrado Bohm and Guiseppe Jacopini. The two
mathematicians demonstrated that any computer program can be written with just three structures:
decisions, sequences, and loops.
Question No:(21) What is Top-Down and bottom up approach of programming?
Answer:-Top-down and bottom-up are strategies of information processing and knowledge ordering,
mostly involving software, but also other humanistic and scientific theories. In practice, they can be seen
as a style of thinking and teaching. In many cases top-down is used as a synonym of analysis or
decomposition, and bottom-up of synthesis.
A top-down approach (also known as stepwise design) is essentially the breaking down of a system to
gain insight into its compositional sub-systems. In a top-down approach an overview of the system is
formulated, specifying but not detailing any first-level subsystems. Each subsystem is then refined in yet
greater detail, sometimes in many additional subsystem levels, until the entire specification is reduced
to base elements. A top-down model is often specified with the assistance of "black boxes", these make
it easier to manipulate. However, black boxes may fail to elucidate elementary mechanisms or be
detailed enough to realistically validate the model.
A bottom-up approach is the piecing together of systems to give rise to grander systems, thus making
the original systems sub-systems of the emergent system. Bottom-up processing is a type of information
processing based on incoming data from the environment to form a perception. Information enters the
eyes in one direction (input), and is then turned into an image by the brain that can be interpreted and
recognized as a perception (output). In a bottom-up approach the individual base elements of the
system are first specified in great detail. These elements are then linked together to form larger
subsystems, which then in turn are linked, sometimes in many levels, until a complete top-level system
is formed. This strategy often resembles a "seed" model, whereby the beginnings are small but
eventually grow in complexity and completeness. However, "organic strategies" may result in a tangle of
elements and subsystems, developed in isolation and subject to local optimization as opposed to
meeting a global purpose.
Question No:(22) What is IEEE- floating point notation?
Answer:-The IEEE standard for floating point arithmetic:The IEEE (Institute of Electrical and Electronics
Engineers) has produced a standard for floating point arithmetic. This standard specifies how single
precision (32 bit) and double precision (64 bit) floating point numbers are to be represented, as well as
how arithmetic should be carried out on them.
The differences in the formats also affect the accuracy of floating point computations.
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Single Precision:
The IEEE single precision floating point standard representation requires a 32 bit word, which may be
represented as numbered from 0 to 31, left to right. The first bit is the sign bit, S, the next eight bits are
the exponent bits, 'E', and the final 23 bits are the fraction 'F':
01 89
The value V represented by the word may be determined as follows:
If E=255 and F is nonzero, then V=NaN ("Not a number")
If E=255 and F is zero and S is 1, then V=-Infinity
If E=255 and F is zero and S is 0, then V=Infinity
If 0<E<255 then V=(-1)**S * 2 ** (E-127) * (1.F) where "1.F" is intended to represent the binary
number created by prefixing F with an implicit leading 1 and a binary point.
If E=0 and F is nonzero, then V=(-1)**S * 2 ** (-126) * (0.F) These are "unnormalized" values.
If E=0 and F is zero and S is 1, then V=-0
If E=0 and F is zero and S is 0, then V=0
In particular,
0 00000000 00000000000000000000000 = 0
1 00000000 00000000000000000000000 = -0
0 11111111 00000000000000000000000 = Infinity
1 11111111 00000000000000000000000 = -Infinity
0 11111111 00000100000000000000000 = NaN
1 11111111 00100010001001010101010 = NaN
0 10000000 00000000000000000000000 = +1 * 2**(128-127) * 1.0 = 2
0 10000001 10100000000000000000000 = +1 * 2**(129-127) * 1.101 = 6.5
1 10000001 10100000000000000000000 = -1 * 2**(129-127) * 1.101 = -6.5
0 00000001 00000000000000000000000 = +1 * 2**(1-127) * 1.0 = 2**(-126)
0 00000000 10000000000000000000000 = +1 * 2**(-126) * 0.1 = 2**(-127)
0 00000000 00000000000000000000001 = +1 * 2**(-126) *
0.00000000000000000000001 =
2**(-149) (Smallest positive value)
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Double Precision
The IEEE double precision floating point standard representation requires a 64 bit word, which may be
represented as numbered from 0 to 63, left to right. The first bit is the sign bit, S, the next eleven bits
are the exponent bits, 'E', and the final 52 bits are the fraction 'F':
11 12
The value V represented by the word may be determined as follows:
If E=2047 and F is nonzero, then V=NaN ("Not a number")
If E=2047 and F is zero and S is 1, then V=-Infinity
If E=2047 and F is zero and S is 0, then V=Infinity
If 0<E<2047 then V=(-1)**S * 2 ** (E-1023) * (1.F) where "1.F" is intended to represent the
binary number created by prefixing F with an implicit leading 1 and a binary point.
If E=0 and F is nonzero, then V=(-1)**S * 2 ** (-1022) * (0.F) These are "unnormalized" values.
If E=0 and F is zero and S is 1, then V=-0
If E=0 and F is zero and S is 0, then V=0
Question No:(18): Explain working of MS-VC editor? How you may run C program in MSVC?
Answer:-Microsoft Visual Studio C/C++ (MSVC), which has an integrated, colour coded editor, in the IDE
(Integrated Development Environment). This is editor-of-choice for generating C/C++ code ... since one
can make quick changes in the code, compile, and link the result, and quickly load it back into the
debugger for testing ... recently, it even allows code changes, while still in the debugger, and MSVC will
re-compile the particular module, and re-link the application.
There are two methods to write and compile a C program in MSVC.
You can compile a C program using command line or you can compile a C program using the Integrated
Development Environment (IDE) from Microsoft Visual C++.
Using Command Line to Compile C Program
1. Select [Start >> All Programs >> Microsoft Visual C++ 2010 Express Edition >> Visual Studio Tools >>
Visual Studio 2010 Command Prompt]. Run with administrator privileges.
2. Once you are in the command line, you can use any editor such as edit to write a C program.
C:> edit myprogram.c
3. After written the program, to compile it, issue the command cl
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C:> cl myprogram.c
4. During the compilation and linking, myprogram.obj and myprogram.exe will be created.To run the
C:> myprogram
Using Visual C++ 2010 IDE
1. Create an empty project by select [File >> New >> Project]. Select [General >> Empty Project] and type
in the project name. Alternatively, you can select [File >> New >> Project], follow by [Win32 >> Win32
Console Application]. Type in the project name.
2. If you use Win32 Console Application, you can skip this step. Under [Solution Explorer], right click the
project name, and select [Properties]. Select [Configuration Properties >> Linker >> System]. Under
[SubSystem], select [Console (/SUBSYSTEM:CONSOLE)].
3. Under [Solution Explorer, Source File], right-click and select [Add >> New Item].
4. Under Code, Select C++ File (.cpp), however, when you type in the name use a program name with
extension .c, such as myprog.c and click [Add].
5. You can proceed to type your C program. Click [Save] icon to save your file.
6. To compile the program, under [Solution Explorer, Source File], right click the source file and select
[Compile or (Ctrl+F7)].
7. Please note that you cannot run the program until you have build solution.
8. To build solution select [Debug >> Build Solution or (F7)]
9. To run the program without debugging, select [Debug >> Start without debugging or (Ctrl+F5)]. (Note:
If you do not have this option, you need to add the command manually under Tools >> Customize. You
may add a menu option or a button in the Debug toolbar.)
10. For any runtime error, you can debug the program as follows; Select [Debug >> Start debugging
11. Please note that during debugging, the program will show and close the console display
12. To see the console display, you must run without debugging.
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The problem using Visual Studio is that many files will be created even for a very simple program. All
files are created inside the project folder.
Under the project name of your program, the source code and object file is located at sub folder similar
to your project name, the executable file is under sub folder <Debug>.
It is simpler to use the command line to compile and run a C program, however, you could use the IDE
for writing a properly formatted C program.
[In addition to above students must exhaustively practice on the
Exercises given in the classroom on Flow Charts, Algorithms and
Number Conversions]
[Also practice first 2 questions from all FCP question papers of last
three years of UTU]
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