Engineering CP unit I

8/13/2019 Engineering CP unit I

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C ProgrammingLecture NotesUnit 1

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UNIT1

INTRODUCTION

1.1.INTRODUCTION TO COMPUTER1.1.1. OVERVIEW OF COMPUTERS

The term Computer is derived from the Latin word Computare which means to

Compute or to Calculate, so it is considered to be a calculating device.

In fact, the main objective of inventing computer was to create a fast calculating machine.

But now-a-days more than 75% of non-mathematical or non-numerical work is carried

out by the computers.

1.1.1.1.Definition

Computer is a fast operating electronic device which automatically accepts and stores

input data, processes them and produces the desired output.

(Or)

Computer is an electronic device which processes information based on the instructions

provided, to generate the desired output. It, therefore, requires two types of input raw

data, and the set of instructions to process or act upon the data.

Figure: Processing Information

Data can be of any type text, numeric, alpha-numeric, image, picture, sound etc. The

instructions that act upon this data are also called the programor softwarein computer

terminology.

1.1.1.2.Data & Information

Data: It is the facts about anything

Information: The processed data or collection of data is called information.

Computer can store, process and retrieve such data or information as and when required.

Process

Instructions

Data

Out ut

Input


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1.1.1.3. Basic operations of a computer:

The computer has the following five basic operations to carry out any task.

i. Input: It is the process of capturing data for the processing.

ii. Process: It is the transformation and manipulation process to convert the input in

to output.

iii. Output: It is the result, which comes from the transformation process or it is the

outcome of the process.

iv. Storing: It is the process of saving the data, instructions, and information, so that

they can be retained and retrieved whenever required.

v. Controlling: It is the process of directing the manner and sequence in which all

the operations are to be performed.

1.1.1.4.Comparison of using computer with human being and calculator

A) Comparison of using computer with human being The computer can perform any arithmetic task with high speed which a man cannot

perform. The advantage of using computer is that it can execute tasks with more accuracy

and speed than human being.

Human being is not restricted by any limits, but computer is restricted by limited step-by-

step instructions called program. Human being can think reason and discover, but the

computer can simply compare, calculate and manipulate.

S.No Characteristic Human Computer

1. Speed Very slow Fast and excellent

2. Accuracy Possibility for error Makes no error

3. Performance Poor Very good

4. Instructions Chances for imperfect Follow perfect

5. Remember Inaccurate Accurate and exact

6. Diligency Human High

B) Comparison of using computer with calculator Unlike a man who is bound to commit mistake, the calculator can do long calculation

with 100% accuracy. The calculator is perfect and it is free from mistake.


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S.No Characteristic Calculator Computer

1. Speed Fast Much faster

2.Performance

Simple calculations and

numeric processing

Complex problem and non-

numeric processing

3.Memory

Less internal memory and nopermanent storage, temporary

storage only

Large internal memory andlarge permanent storage

available

4. Machine Electronic device Electronic device

5. Operation Arithmetic Arithmetic and logical

1.1.2.CHARACTERISTICS OF COMPUTERSThe characteristics of computers that have made them so powerful and universally useful

are speed, accuracy, diligence, versatility and storage capacity.

Speed

Computers work at an incredible speed. The speed with which it performs is way beyond

human capabilities. As a comparison, it can do in one minute what a human being would

probably take year!

The following are the measurements by which the speed of a computer is measured.

1 millisecond = 110-3

second

1 microsecond= 110-6

second

1 nanosecond =110-9

second

1 picoseconds = 110-12

second

We do not measure speed in seconds or in milli seconds today, we measure speed in nano

second and pico second. A powerful computer is capable of adding together two 20-digit

numbers in 300 nano seconds.

Accuracy

In addition to being fast, computers are also accurate. Errors that may occur can almost

always be attributed to human error (inaccurate data, poorly designed system or faulty

instructions/programs written by the programmer) rather than technological weaknesses.

In fact, a special term GIGO (Garbage In Garbage Out) has been coined to represent a

scenario where faulty results are got due to inaccurate instructions or faulty data.


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Automatic

A computer works automatically, once programs are stored and data are given to it,

constant supervision is not required.

Diligence

Unlike human beings, computers are highly consistent. They do not suffer from human

traits of boredom and tiredness resulting in lack of concentration. Computers, therefore,

score high over human beings in performing voluminous and repetitive jobs.

If three million calculations have to be performed, it will perform the third millionth

instruction with exactly the same accuracy and speed as the first instruction.

Versatility

A computer canbe put to work in various fields. As is evident, in todays fast developing

technology-world, it is almost inconceivable to find an area where computers are not

being used. The presence of computers can be seen in every sphere Railway/Air

reservation, Banks, Hotels, Weather forecasting and many more.

Storage Capacity

Todays computers can store volumes of data. Unlike human memory where unimportant

information is relegated to the back of the mind and forgotten as time progresses, a piece

of information once recorded (or stored) in the computer, can never be forgotten and can

be retrieved almost instantaneously! Information can, therefore, be retained as long as

desired (using secondary storagea type of detachable memory).

Reduction of cost

Though initial investment may be high, computer substantially reduces the cost of

transaction.

No intelligent quotient

The computer cannot think of its own and it can duly perform the instructions given by

the human being.

1.1.3.APPLICATIONS OF COMPUTER Following list demonstrates the various applications of Computers in today's arena.

Business

The computer's characteristic as high speed of calculation, diligence, accuracy, reliability,

or versatility has made it an integrated part in all business organisations.


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Computer used in business organisation for:

Payroll Calculations

Budgeting

Sales Analysis

Financial forecasting

Managing employees database

Maintenance of stocks etc.

Banking

Today Banking is almost totally dependent on computer.

Banks provide following facilities:

Banks on-line accounting facility, which include current

balances, deposits, overdrafts, interest charges, shares

and trustee records.

ATM machines are making it even easier for customers to

deal with banks.

Insurance

Insurance companies are keeping all records up to date with the help of computer. The

Insurance Companies, Finance houses and Stock broking firms are widely using

computers for their concerns.

Insurance Companies are maintaining a database of all clients with information showing

how to continue with policies

starting date of the policies

next due installment of a policy

maturity date

interests due

survival benefits

bonus


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Education

The computer has provided a lot of facilities in the Education System.

The uses of computer provide a tool in the Education system is known as CBE

(Computer Based Education).

CBE involves Control, Delivery and Evaluation of learning.

The computer education is very familiar and rapidly increasing

the graph of computer students.

There are number of methods in which educational institutions

can use computer to educate the students.

It is used for prepare a database about student performance and analysis are carried out.

Marketing

In Marketing uses of computer are following:

Advertising:With computers, advertising professionals create art and graphics, write and

revise copy, and print and disseminate ads with the goal of selling more products.

At Home Shopping:At home shopping has been made possible through use of

computerised catalogues that provide access to product information and permit direct

entry of orders to be filled by the customers.

Health Care

Computers have become important part in all Medical Systems.

The computers are being used in hospitals to keep the record of patients and medicines. It

is also used in scanning and diagnosing different diseases. ECG, EEG, Ultrasounds and

CT Scans etc. are also done by computerised machines.

Some of major fields of health care in which computer are used:


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Diagnostic System:Computers are used to collect data and identify cause of

illness.

Lab-diagnostic System:All tests can be done and reports are prepared by

computer.

Patient Monitoring System:These are used to check patient's signs for

abnormality such as in Cardiac Arrest, ECG etc.

Pharma Information System:Computer checks Drug-Labels, Expiry dates,

harmful drug side effects etc.

Nowadays, computers are also used in performing surgery.

Engineering Design

Computers are widely used in Engineering purposes.

One of major areas is CAD(Computer aided design).CAD provides creation,edition, and

modification of image. Some fields are:

Structural Engineering:Requires stress and strain analysis required for

design of Ships, Buildings, Budgets, Airplanes etc.

Industrial Engineering:Computers deals with design, implementation

and improvement of Integrated systems of people, materials and

equipments.

Architectural Engineering:Computers help in planning towns, designing

buildings, determining a range of buildings on a site using both 2D and 3D

drawings.


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Military

Computers are largely used in defence.Modern tanks, missiles, weapons etc.employ

computerised control systems.Some military areas where a computer has been used are:

Missile Control

Military Communication

Military operation and planning

Smart Weapons

Communication

Communication means to convey a message, an idea, a picture or speech that is received

and understood clearly and correctly by the person for whom it is meant.Some main areas

in this category are:

E-mail

Chatting

Usenet

FTP

Telnet

Video-conferencing


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Government Applications

Computers play an important role in government applications. Some major fields in this

category are:

Budgets

Sales tax department

Income tax department

Male/Female ratio

Computerization of voters lists

Computerization of Driving Licensing system

Computerization of PAN card

Weather Forecasting.

1.1.4.EVOLUTION OF COMPUTERS The history of computers can be traced back to almost 2000 years ago, with the advent of

abacus, a wooden rack holding two horizontal wires with beads strung on them.

Numbers are represented using the position of beads on the rack. Fast and simple

calculations can be carried out by appropriately placing the beads.

In 1620, an English mathematician by the name Wil liam Oughtredinvented the slide rule

a calculating device based on the principle of logarithms. It consisted of two graduated

scales devised in such a manner that suitable alignment of one scale against the other,

made it possible to perform additions, compute products etc. just by inspection.

Figure: The Abacus

Blaise Pascal, a French mathematician, is usually credited for building the first digital

computer in 1642. He invented the mechanical calculating machine. Numbers were


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entered in this machine by dialing a series of numbered wheels. Another series of toothed

wheels transferred the movements to a dial, which showed the results.

In 1671, Gottfried von Leibnitz, a German mathematician, invented a calculating

machine which was able to add and perform multiplications. He invented a special

stepped gear mechanism for introducing the addend digits, which is still being used.

The prototypes made by Pascaland Leibnitzwere not used in many places. It was only

about a century later that Thomas of Colmar created the first successful mechanical

calculator which could add, subtract, multiply, and divide. A lot of improved desktop

calculators by various inventors followed, such that by 1890 a range of improvements

like accumulation of partial results, storage of past results, and printing of results were

not uncommon.

The First Computer

Charles Babbage, a professor of mathematics at Cambridge University, England,

realized that many long calculations usually consisted of a series of actions that were

constantly repeated and hence could possibly be automated. By 1822, he designed an

automatic calculating machine that he called the Difference Engine. It was intended to

be steam powered and fully automatic (including printing of result tables), commanded

by a fixed instruction program. In short, he developed a prototype of a computer which

was 100 years ahead of time and is, therefore, considered as the father of modern day

computers.

A step towards automated computing was the development of punched cards which were

first successfully used by Herman Holleri th, who worked in the US Census Bureauin

1890. He along with James Powersdeveloped devices that could read information that

had been punched into cards, without any human help. This resulted in reduced readingerrors, increased workflow and availability of unlimited memory (punched cards could be

used as easily accessible memory of unlimited size).

These advantages were seen by various commercial companies and soon led to the

development of improved punch-card using computers by companies like International

Business Machines (IBM) and Remington.

Some Well Known Early Computers

Mark I

After World War II there was a need felt for advanced calculations. By that time, many

reliable mechanical desk calculators had been developed. Howard A. Aikenof Harvard

University, while working on his doctorate in physics, in the year 1937, designed a

machine that could automatically perform a sequence of arithmetic operations. He

completed this in 1944 and named it Mark I. This machine performed a multiplication

and division at an average of about four and eleven seconds respectively. The results

were printed at a rate of one result per five seconds.


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ENIAC

The World War II also produced a large need for computer capacity especially for the

military. New weapons were made for which trajectory tables and other essential data

were needed. In 1942, Professors

John P. Eckert and John W. Mauchly at the Moore School of Engineering of the

University of Pennsylvania, USA, decoded to build a high speed computer to do the job.This was called the Electronic Numeric Integrator and Calculator (ENIAC).

It used 18,000 vacuum tubes, about 1,800 square feet of floor space, and consumed about

180,000 watts of electrical power. It had punched cards I/O and its programs were wired

on boards.

ENIAC is accepted as the first successful high-speed electronic digital computer and was

used from 1946 to 1955.

EDVAC

Fascinated by the success of ENIAC, John Von Neumann, a mathematician, undertookan abstract study of computation in 1945. In this he aimed to show that a computer

should be able to execute any kind of computation by means of a proper programmed

control. His ideas, referred to as stored program technique, became essential for

future generations of high-speed digital computers and were universally accepted. The

basic idea behind the stored program concept was that data as well as instructions can be

stored in the computers memory to enable automatic flow of operations.

Between 1947 and 1950, the More School personnel and the Ballistics Research

Laboratory of the US army built a computer named Electronic Discrete Variable

Automatic Computer (EDVAC), which was based on Von Neumanns concept of storedprogram.

UNIVAC

The Universal Automatic Computer (UNIVAC), developed in 1951, was the first digital

computer to be produced and was installed in the Census Bureau.

The first-generation stored-program computers needed a lot of maintenance, reached 70%

to 80% reliability of operations and were used for almost 10 years. EDVAC and

UNIVAC fell into this group of computers and were the first commercially available

computers.

1.1.5.GENERATIONS OF COMPUTERS Generation in computer terminology is a step ahead in technology. As you go through

the history of evolution of computers, you will find that the earliest computers were big

in size, consumed a lot of power and heated up quickly, due to which it had to be shut


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down, frequently to be cooled. They were very expensive in terms of development and

maintenance.

As technology improved, computers became compact, faster and more powerful. From a

users perspective, they become user friendly and more affordable. This has largely

contributed towards the popularity that computers have gained these days.

The term generation was earlier used only to distinguish between varying hardware

technologies but was later extended to include both hardware and software. A

comparison of generations is made below.

First Generation Computers (1940 to 1956)

The first generation of computers was characterized by vacuum tubes in the circuitry

and magnetic drums for memory.

These computers were enormous in size, used great deal of electricity and were expensive

to operate. They also had limited storage capacity.

Figure : Vacuum Tube

First generation computers relied on machine language (binary-coded program) to

perform operations and could solve only one problem at a time. Punched cards and paper

tapes were used to input data and instructions, and output was displayed on printouts.

Early computers like ENIAC, EDVAC and UNIVAC can all be classified as first

generation computers.

Second Generation Computers (1956 to 1963)

In the early 1950s, the discoveries of Transistorand Magnetic corememory changed

the image of computers from unreliable to highly reliable machines with increased

capability, and higher storage capacity.

The transistor was far superior to the vacuum tube, allowing computers to become

smaller in size, cheaper, reliable and more energy efficient. Though transistor still

generated a great deal of heat, it was a substantial improvement over the vacuum tube.

Second generation of computers was also characterized by allowing programmers to

specify instructions in symbolic (or assembly) language rather than cryptic binary


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machine language. High level programming languages like COmmon Business Oriented

Language (COBOL) and FORmula TRANslation (FORTRAN) were also being

developed at this time.

Due to the increase in the cost of expanding programming, these machines were

expensive to purchase and operate. Such computers were, therefore, mostly found in

large computer centres or government/private laboratories with many programmers andsupport professionals.

Third Generation Computers (1964 to 1971)

The development of Integrated Circuitby Jack Kilby, an engineer with Texas

Instruments, in 1958, was the hallmark of the third generation of computers. Punched

cards and printouts gave way to devices like keyboards and monitors making it easier for

the user to interact with the computer. Computer manufacturers could provide a range of

accessories like the cathode ray tube display devices, page printers, consoles etc.

Existence of an operating systemallowed the device to run various applications at one

time with the central program monitoring the memory.

For the first time, computers were being widely used in business for areas like :

Accounting

Payroll

Billing

Tracking Inventory, etc.

Third generation computers were substantially smaller and cheaper than their

predecessors.

Fourth Generation Computers (1971 to present)

The trend in 1970s was to move from single-purpose but powerful computers towards

cheaper computer systems that could support a large range of applications.

A new revolution in computer hardware came about which could shrink the computer

logic circuitry and its components using the Large Scale Integration (LSI) technology.

Hundreds of components could now fit onto a single chip!

Figure : IC Chips Figure : Intel Pentium Microprocessor Chip


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In the 1980s, Very Large Scale Integration (VLSI) squeezed hundreds of thousands of

components onto a single chip. This shrinking trend continued and led to the introduction

of personal computers (PCs) programmable machines that are small enough and

inexpensive so that these can be purchased and used by individuals. Companies like

Apple Computers and IBM introduced very successful PCs.

The IC technology was not only used to construct the processor, but also for theconstruction of memory. The first memory chip was constructed in 1970 and could hold

256 bits.

Fifth Generation Computers (the Road Ahead)

The fifth generation of computers characterized by artificial intelligence is in the process

of development. The goal here is to develop devices that are capable of learning and

responding to natural language input. This generation of computers is using new

technologies in very large scale integration, along with new programming languages and

will be capable of amazing feats, in the area of artificial intelligence, such as voice

recognition.

Computer

Generation

Technology

Used

Speed Storage

Capacity

Programming

Language

First Vacuum tubes Slow Limited Symbolic language

Second Transistors Relatively

faster

Increased

storage

capacity

High Level Languages

(e.g. COBOL,

FORTRAN)

Third IntegratedCircuits (ICs)

Betterperformance,

Remote

processing and

time sharing

Increasedstorage

Extensive use of HighLevel Languages

Fourth Large scale and

very large scale

integrated

circuits (LSI,

VLSI)

Considerably

faster

Increased

storage

Sophisticated

programs and

languages for special

applications

Fifth Use of ICs with

ultra large scale

integration

technology

(ULSI)

Extremely fast Larger

capacity

storage

(RAID,

optical

disks)

Based on Artificial

Intelligence


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1.1.6.CLASSIFICATION OF COMPUTERSi) On the basis of working principle

a) Analog Computer

An analog computer is a form of computer that uses continuous physical phenomena such as

electrical, mechanical, or hydraulic quantities to model the problem being solved.Eg: Thermometer, Speedometer, Petrol pump indicator, Multimeter

b) Digital Computer

A computer that performs calculations and logical operations with quantities represented as

digits, usually in the binary number system.

c) Hybrid Computer (Analog + Digital)

A combination of computers those are capable of inputting and outputting in both digital andanalog signals. A hybrid computer system setup offers a cost effective method of performing

complex simulations. The instruments used in medical science lies in this category.

ii) On the basis of Size

a) Super ComputerThe fastest type of computer. Supercomputers are very expensive and are employed for

specialized applications 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

exploration. PARAM, Pace & Flosolver are the supercomputer made in india.


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b)Mainframe Computer

A very large and expensive computer capable of supporting hundreds, or even thousands, of

users simultaneously. In the hierarchy that starts with a simple microprocessor (in watches, for

example) at the bottom and moves to supercomputers at the top, mainframes are just below

supercomputers. In some ways, mainframes are more powerful than supercomputers because

they support more simultaneous programs. But supercomputers can execute a single program

faster than a mainframe.

c) Mini Computer

A midsized computer. In size and power, minicomputers lie between workstations and

mainframes. In the past decade, the distinction between large minicomputers and small

mainframes has blurred, however, as has the distinction between small minicomputers and

workstations. But in general, a minicomputer is a multiprocessing system capable of supporting

from 4 to about 200 users simultaneously. Generally, servers are comes in this category.

d) Micro Computer

i. Desktop Computer:a personal or micro-mini computer sufficient to fit on a desk.

ii. Laptop Computer: a portable computer complete with an integrated screen andkeyboard. It is generally smaller in size than a desktop computer and larger than a

notebook computer.

iii. Palmtop Computer/Digital Diary /Notebook /PDAs: a hand-sized computer.

Palmtops have no keyboard but the screen serves both as an input and output device.


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e) Workstations

A terminal or desktop computer in a network. In this context, workstation is just a generic term

for a user's machine (client machine) in contrast to a "server" or "mainframe."

1.1.7.BASIC COMPUTER ORGANIZATION The computer system essentially comprises three important parts input device, central

processing unit (CPU) and the output device. The CPU itself is made of three

components namely, the arithmetic logic unit (ALU), memory unit, and the control unit.

In addition to these, auxiliary storage/secondary storage devices are used to store data and

instructions on a long-term basis.

Figure: Basic Computer Organization

Input Unit

Data and instructions must be entered into the computer system for processing, and

results obtained from computations must be displayed or recorded for the user. The input

device serves the purpose of receiving data and instructions in a form that can be

understood by the computer.

Secondary

Storage

Input Unit Output Unit

Central Processing Unit

Arithmetic

Logic Unit

Main

Memory

Control Unit


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Central Processing Unit

Data and instructions (programs) are stored in the computers memory after which all the

major calculations and computations are carried out within the CPU. The CPU is also

responsible for controlling the operations of various units of the computer system.

a) Arithmetic Logic Unit (ALU) All calculations and comparisons, based on the instructions provided, are carried out

within the ALU. It performs arithmetic functions like addition, subtraction,

multiplication, division and also logical operations like greater than, less than and equal

to.

b) Main Memory The main memory holds data and instructions after input, till they are needed. It also

holds the processed results that are awaiting output.

c) Control Unit The function of the control unit is to execute the instructions of a program, one by one, in

the desired sequence. It interprets each instruction and then prompts its execution by one

of the units like input, output, ALU, storage.

For example, a comparison of two numbers (a logical operation) to be performed by the

ALU may require loading the two numbers into the main memory which is a function

performed by the control unit. It will then pass on the execution of the compare function

to the ALU.

Output Unit

The processed data, stored in the memory of the computer is sent to the output unit,

which then converts it into a form that can be understood by the user. The output is

usually produced in one of the two wayson the display device, or on paper (hard copy).

Secondary Storage

Also termed as auxiliary or backup storage, it is typically used as a supplement to

main storage. It is much cheaper than the main storage and stores large amount of data

and instructions permanently. Hardware devices like magnetic tapes and disks fall under

this category.

1.1.8.COMPONENTS OF COMPUTERSINPUT AND OUTPUT DEVICES

The computer will be of no use unless it is able to communicate with the outside world.

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


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information OUT of a computer system. These input/output devices are also known as

peripheralssince they surround the CPU and memory of a computer system.

Some commonly used Input/Output devices are listed in table below.

Input Devices Output Devices

Keyboard

Mouse

Joystick

Scanner

Light Pen

Touch Screen

Monitor

LCD

Printer

Plotter

Input Devices

Keyboard

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.

Figure : Qwerty Keyboard Layout

Alphanumer ic 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 tothese keys differ from one software package to another. These keys are also user

programmable keys.

Special-f unction 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.

Function Keys

Numeric Keypad

Cursor Movement

Keys

Alphanumeric Keypad/

Special-function Keys


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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 feature. 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.

Ctrl: Control key is used in conjunction with other keys to provide additional

functionality on the keyboard.

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 onthem. 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).

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 frequently.

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.


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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.

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.

Figure : Mouse Figure : Joystick

Scanner

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.

Figure : A Flat-bed Scanner

Hand-held scanners are commonly seen in big stores to scan codes and price informationfor each of the items.

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.


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Users of Computer Aided Design (CAD) applications commonly use the light pens to

directly draw on screen.

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.

Output Devices

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.

Figure : Monitor

L iquid 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 (laptops).

Printer

Printers are used to produce paper (commonly known as hardcopy) output. Based on the

technology used, they can be classified as Impactor Non-impactprinters.

Impact printersuse the typewriting printing mechanism wherein a hammer strikes the

paper through a ribbon in order to produce output. Dot-matrix and Character printers fall

under this category.


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Non-impactprinters 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 resolutionis measured in terms of number of dots per

inch (dpi). Print speedis measured in terms of number of characters printed in aunit of time and is represented as characters-per-second (cps), lines-per-minute

(lpm), or pages-per-minute (ppm).

Plotter

Plotters are used to print graphical output on paper. It interprets computer commands

and makes line drawings on paper using multicoloured automated pens. It is capable

of producing graphs, drawings, charts, maps etc.

Figure : An Inkjet Printer Figure : A Flatbed Plotter

Computer Aided Engineering (CAE) applications like CAD (Computer Aided Design)

and CAM (Computer Aided Manufacturing) are typical usage areas for plotters.

RAM/ROM

Computers memory can be classified into two types RAM and ROM.

RAMor Random Access Memory is the central storage unit in a computer system. It is

the place in a computer where the operating system, application programs and the data in

current use are kept temporarily so that they can be accessed by the computers

processor. The more RAM a computer has, the more data a computer can manipulate.

Random access memory, also called the Read/Write memory, is the temporary memory

of a computer. It is said to be volatile since its contents are accessible only as long asthe computer is on. The contents of RAM are cleared once the computer is turned off.

ROMor Read Only Memory is a special type of memory which can only be read and

contents of which are not lost even when the computer is switched off. It typically

contains manufacturers instructions. Among other things, ROM also stores an initial

program called the bootstrap loader whose function is to start the computer software

operating, once the power is turned on.


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Read-only memories can be manufacturer-programmedor user-programmed. While

manufacturer-programmed ROMs have data burnt into the circuitry, user-programmed

ROMs can have the user load and then store read-only programs. PROM or

Programmable ROM is the name given to such ROMs.

Information once stored on the ROM or PROM chip cannot be altered. However, another

type of memory called EPROM (Erasable PROM) allows a user to erase the informationstored on the chip and reprogram it with new information. EEPROM (Electrically

EPROM) and UVEPROM (Ultra Violet EPROM) are two types of EPROMs.

SECONDARY STORAGE DEVICES

RAM is volatile memory having a limited storage capacity. Secondary/auxiliary storage

is storage other than the RAM. These include devices that are peripheral and are

connected and controlled by the computer to enable permanent storage of programs and

data.

Magnetic medium was found to be fairly inexpensive and long lasting medium and,

therefore, became the preferred choice for auxiliary storage. Floppy disks and hard disks

fall under this category. The newer forms of storage devices are optical storage devices

like CDs, DVDs, Pen drive, Zip drive etc.

Floppy Disk

These are small removable disks that are plastic coated with magnetic recording material.

Floppy disks are typically 3.5 in size (diameter) and can hold 1.44 MB of data. This

portable storage device is a rewritable media and can be reused a number of times.

Floppy disks are commonly used to move files between different computers. The main

disadvantage of floppy disks is that they can be damaged easily and, therefore, are not

very reliable.

Hard Disk

Hard disks are made up of rigid material and are usually a stack of metal disks sealed in a

box. The hard disk and the hard disk drive exist together as a unit and are a permanent

part of the computer where data and programs are saved. These disks have storage

capacities ranging from 1GB to 80 GB and more. Hard disks are also rewritable and are

more reliable when compared with floppies.

Figure : A Floppy Disk Figure : A Winchester Disk


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Depending on the way they are packaged, hard disks can be classified as Disk packsor

Winchester disks. Disk packs are removable, in the sense that they can be removed and

kept offline when not in use. They must be mounted on the disk drive before use.

Winchester disks on the other hand, consist of disk platters sealed in a contamination-free

container and form a permanent component of the computer.

CD

Compact Disk (CD) is portable disk having data storage capacity between 650-700 MB.

It can hold large amount of information such as music,

full-motion videos, and text etc. It contains digital information that can be read, but

cannot be rewritten. Separate drives exist for reading and writing CDs.

Since it is a very reliable storage media, it is very often used as a medium for distributing

large amount of information to large number of users. In fact today most of the software

is distributed through CDs.

DVD

Digital Versatile Disk (DVD) is similar to a CD but has larger storage capacity and

enormous clarity. Depending upon the disk type it can store several Gigabytes of data (as

opposed to around 650MB of a CD). DVDs are primarily used to store music or movies

and can be played back on your television or the computer too. They are not rewritable

media.

1.2.COMPUTER SOFTWARE:

Software is a set of programs, which is designed to perform a well defined function. A programis a sequence of instruction written to solve a particular problem.

TYPES OF SOFTWARE:

1. System software

2.Application software

SYSTEM SOFTWARE

System software directly controls the computers hardware, whereas application software

is one level removed from hardware. System software manages the computers resources,

enables the various components of the computer to communicate, runs application software, and

makes the hardware respond to the users needs. When the system software operates efficiently,

the difficult operations of controlling the hardware are transparent to the user. System software

includes four main types:


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The operating systemprovides an interface between the computer hardware and the user

or the application software. Because of its central importance, the operating system will

be discussed in more detail below.

Language translators convert application programs and any other software programs

into the machine language that actually controls the computer's operations.

assemblers translates the program in assembly-languageinto machine-language

compilers translates high-levellanguage program into machine-languageall at once

interpreters translates high-levellanguage into machine-languagea line at a time

Network and communications software operates the communications hardware in a

computer so that it can transmit and receive information from other computers. Network

and communications software requires two types of software: software for the PC

operating system and software for the network operating system. In some cases, the latter

comes built-in the former. Utility programs perform various specialized "housekeeping" tasks, such as file

management, virus protection, disk defragmentation, program installation and

uninstallation, file and disk back up, disk formatting, and providing screen saver

programs. This list is far from exhaustive. The user directly controls most utility

programs, although some utility programs can be set to run automatically (e.g.; screen

savers and anti-virus scanning).

APPLICATION SOFTWARE

Application software can be written for a specific users application (custom software), or

it can be mass-produced for general use (commercial or packaged software).Word processingprograms allow the user to quickly and easily create and revise texts

on the computer screen. By using word processing applications, the user can format documents

with ease, changing font size, margins, color, etc. Different types of documentse.g., letters,

memos, and reportsare often preformatted in the application. PC-based word processingsoftware is so capable and inexpensive that, in most businesses, it has become the usual tool for

creating documents, even when more powerful mainframes and minicomputers are available.

Spreadsheet programsare especially useful in business and accounting. The electronic

spreadsheet consists of rows and columns of data, which the user can easily edit, copy, move, orprint. Using numeric data entered in the spreadsheet, the computer can perform numerous

mathematical calculations automatically, many of impressive sophistication (e.g., statistical,

logical, and engineering functions). One of the spreadsheet programs most powerful features forbusiness purposes is that it enables the user to do what-if analyses on existing data and to inputdifferent data for various scenarios. Non-numeric data (e.g., names and dates) may also be

entered in a spreadsheet. Spreadsheets can perform some non-mathematical operations (e.g.,

sorting and filtering) on this data, although this type of analysis is not a spreadsheet's strength.

Database software allows the user to enter, store, maintain, retrieve, and manipulate

data. In some ways, databases pickup where spreadsheets leave off, although a fairer assessment

is probably that the relationship between the two types of software is reciprocal. Database


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software is certainly more efficient and effective at handling non-numeric data than isspreadsheet software. Conversely, numeric data is usually easier to manipulate in a spreadsheet.

In most databases, data is entered to tables of rows and columns, similar to spreadsheets. Unlike

spreadsheets, these tables can be connected into relationships that allow users incredibleversatility in what they can do with that data. For example, databoth numeric and non-

numericfrom several individual tables may be retrieved and used together in calculations, with

the results presented in a business-style report.Presentation graphics software enables users to design professional-quality

presentations for business and educational purposes. The presentations usually consist of

formatted slides for projecting onto a screen from a computer projector or overhead projector, orfor display on a large monitor. These presentations may also be used for online meetings and

Web broadcasts. The slides can be designed to include backgrounds, graphic images, charts,

clipart, shading, animation, and audio effectsand, of course, text, which can sometimes get lost

in all of the embellishments.

1.3.SOFTWARE DEVELOPMENT LIFE CYCLE

The systems development life cycle (SDLC), or software development process, or Software

Development Life Cyclein systems engineering, information systems and software engineering,

is a process of creating or altering information systems, and the models and methodologies that

people use to develop these systems. In software engineering, the SDLC concept underpins many

kinds of software development methodologies.

SOFTWARE DEVELOPMENT PHASES:

Preliminary Analysis: The objective of phase 1 is to conduct a preliminary analysis, propose

alternative solutions, describe costs and benefits and submit a preliminary plan with

recommendations.

Systems analysis, requirements definition: Defines project goals into defined functions and

operation of the intended application. Analyzes end-user information needs.

Systems design: Describes desired features and operations in detail, including screen layouts,

business rules, process diagrams, pseudocode and other documentation.

Development: The real code is written here.

Integration and testing: Brings all the pieces together into a special testing environment, then

checks for errors, bugs and interoperability.

Acceptance, installation, deployment: The final stage of initial development, where the

software is put into production and runs actual business.


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Maintenance: During the maintenance stage of the Life-Cycle, the system is assessed to ensure

it does not become obsolete. This is also where changes are made to initial software. It involves

continuous evaluation of the system.

Evaluation: Some companies do not view this as an official stage of the SDLC, but is it an

important part of the life cycle. Evaluation step is an extension of the Maintenance stage, and

may be referred to in some circles as Post-implementation Review. This is where the system that

was developed, as well as the entire process, is evaluated.

Disposal Phase:In this phase, plans are developed for discarding system information, hardware

and software in making the transition to a new system. The purpose here is to properly move,

archive, discard or destroy information, hardware and software that is being replaced, in a matter

that prevents any possibility of unauthorized disclosure of sensitive data.

Software Development life cycle

1.4. NEED FOR STUDYING COMPUTER PROGRAMMING LANGUAGES

PROGRAMMING LANGUAGES:

A programming languageis a formal language designed to communicate instructions to

a machine, particularly a computer. Programming languages can be used to create programs that

control the behavior of a machine and/or to express algorithms precisely.


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TYPES OF PROGRAMMING LANGUAGES:

1. Machine Language

2. Assembly Language

3. High Level Language

1. Machine Language:

It is a native language of computers.It uses only 0s and 1s to represent data and instructions.

2. Assembly Language:An assembly languageis a low-level programming language for a computer, or other

programmable device, in which there is a very strong correspondence between the language and

the architecture's machine code instructions. Assembly language is converted into executable

machine code by a utility program referred to as an assembler; the conversion process is referred

to as assembly, or assemblingthe code.

3. High Level Language:

Aprogramming languagesuch as C, FORTRAN, or Pascalthat enables aprogrammerto

writeprogramsthat are more or less independent of a particular type of computer.Such languagesare considered high-level because they are closer to human languages and

further from machine languages. In contrast, assembly languagesare considered low-level

because they are very close to machine languages.

GENERATIONS OF PROGRAMMING LANGUAGES:

First generation:Machine Language

The first language was binary, also known as machine language, which was used in

earliest computers and machines.

OPCODE(Operation

Code)

OPERAND(Memory

Location)

The first part is an opcode, which tells the computer what functions are to be performed. The

second part is operand which tells the computer where to find or store the data on which the

desired operation is to be performed.

Advantages:

Translation free

High speed

Disadvantages:

Machine dependent Complex Language

Error prone

Tedious

Second Generation: Assembly Language

Developed on early 1950s and its main developer was IBM.

Assembly language allows the programmer to interact directly with the hardware.


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It provides mnemonic instructions usually three letters long corresponding to each

machine instructions.

Eg:ADD which is used to perform addition operation

The general format of assembly instruction is

[Label] [;comment]

Label opcode operands comments

BEGIN ADD A,B ;add B to A

(Source code) (object code)

Advantages:

Easy to understand and use

Less error prone

Faster

More control on hardware

Disadvantages:

Machine Dependent

Harder to learn

Slow development time

Less efficient

No standardization

Third Generation:High Level Language

In computer science, a high-level programming languageis a programming

language with strong abstraction from the details of the computer. In comparison to low-

level programming languages, it may use natural language elements, be easier to use, or

may automate (or even hide entirely) significant areas of computing systems (e.g.

ASSEMBLERAssembly

program

Machine

language

program


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memory management), making the process of developing a program simpler and more

understandable relative to a lower-level language.

Eg: COBOL, FORTRAN,BASIC and C.

Advantages:

Readability

Machine Independent

Easy Debugging

Easier to Maintain

Low development cost

Disadvantages:

Poor control on hardware

Less Efficient

Fourth Generation: 4GL

Commonly used to access databases.

Have minimum number of syntax rules.

Helpful to write application programs.

Three categories of 4GL:

Query Languages

Report Generators

Application Generators

Advantages:

User can create their application in a much shorter time for their development.

It does not require the programmer to provide the logic to perform a task.Disadvantages:

Programs are quite lengthy, since need more disk space and large memory capacity.

Fifth Generation:Very high languages

It is just a conceptual view of what might be the future of programming languages.

These languages will be able to process natural languages.

Need for Studying Computer Programming Languages:

Computer is a machine which cannot understand English.

Usage of Machine language to give instructions to the computer was found very difficult

by human.

Programming languages were invented to make machines easier to use and no need to

give instructions in the form of 0s and 1s.


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1.5. PROBLEM SOLVING TECHNIQUES

Problem solving technique is a set of techniques and graphical tools that helps in providing logic

for solving a problem. These tools are used to express the logic of the problem by specifying the

correct sequence of all instructions to be carried out.

1. Algorithm2. Flowchart

Algorithm

Set of step-by-step instructions that perform a specific task or operation in Natural

language

NOT programming language

Advantages of algorithm

it is a step-by-step representation of a solution to a given problem ,which is very easy to

understand

it has got a definite procedure.

it easy to first develop an algorithm, then convert it into a flowchart &then into a

computer program.

it is independent of programming language.

it is easy to debug as every step is got its own logical sequence.

Disadvantages of algorithms

Not suitable for complex problems

Cannot be updated

It is time consuming & cumbersome as algorithm is developed first which is converted intoflow chart &then into a computer program.

Flowchart

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.

ADVANTAGES OF USING FLOWCHARTS

The benefits of flowcharts are as follows:


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1. Communication: Flowcharts are better way of communicating the logic of a system to

all concerned.

2. Effective analysis: With the help of flowchart, problem can be analyses in more

effective way.

3. Proper documentation: Program flowcharts serve as a good program documentation,

which is needed for various purposes.

4. Efficient Coding: The flowcharts act as a guide or blueprint during the systems

analysis and program development phase.

5. Proper Debugging: The flowchart helps in debugging process.

6. 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

LIMITATIONS OF USING FLOWCHARTS

1. Complex logic: Sometimes, the program logic is quite complicated. In that case,

flowchart becomes complex and clumsy.

2. Alterations and Modifications: If alterations are required the flowchart may require re-drawing completely.

3. Reproduction: As the flowchart symbols cannot be typed, reproduction of flowchart

becomes a problem.

4. The essentials of what is done can easily be lost in the technical details of how it is

done.

GUIDELINES FOR DRAWING A FLOWCHART

The following are some guidelines in flowcharting:

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

bottom.

d. Only one flow line should come out from a process symbol.

or

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.


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SYMBOLS USED IN FLOW CHART

Figure:Start/Stop terminal box

Figure:Input/output box

Figure:Process/Instruction box

Figure:Lines or Arrows

Figure:Decision box

Figure: Connector box
http://3.bp.blogspot.com/-lF6ruaOQHC0/UGyWTq_1EXI/AAAAAAAAAh0/A48lWRxi5Q8/s1600/connector_03.jpghttp://3.bp.blogspot.com/-Ffd5jluyK8Y/UGyVcmhsL5I/AAAAAAAAAhs/YM9BE4o_898/s1600/decision_03.jpghttp://3.bp.blogspot.com/-WxJxEWb6kog/UGyUKDim_3I/AAAAAAAAAhk/tIFW7IKLdHg/s1600/arrows_03.jpghttp://2.bp.blogspot.com/-_9v1CN97nDg/UGyS39rrvrI/AAAAAAAAAhc/Hp_-6eIbRIg/s1600/process_03.jpghttp://3.bp.blogspot.com/-Yid4V_bSR_c/UGyRqbo5VJI/AAAAAAAAAhU/whLrCtdgJ64/s1600/output-input_03.jpghttp://3.bp.blogspot.com/-b6TQd1_QrPw/UGyQt8YViLI/AAAAAAAAAhM/eYSjwtZ_rsI/s1600/terminal+start.jpghttp://3.bp.blogspot.com/-lF6ruaOQHC0/UGyWTq_1EXI/AAAAAAAAAh0/A48lWRxi5Q8/s1600/connector_03.jpghttp://3.bp.blogspot.com/-Ffd5jluyK8Y/UGyVcmhsL5I/AAAAAAAAAhs/YM9BE4o_898/s1600/decision_03.jpghttp://3.bp.blogspot.com/-WxJxEWb6kog/UGyUKDim_3I/AAAAAAAAAhk/tIFW7IKLdHg/s1600/arrows_03.jpghttp://2.bp.blogspot.com/-_9v1CN97nDg/UGyS39rrvrI/AAAAAAAAAhc/Hp_-6eIbRIg/s1600/process_03.jpghttp://3.bp.blogspot.com/-Yid4V_bSR_c/UGyRqbo5VJI/AAAAAAAAAhU/whLrCtdgJ64/s1600/output-input_03.jpghttp://3.bp.blogspot.com/-b6TQd1_QrPw/UGyQt8YViLI/AAAAAAAAAhM/eYSjwtZ_rsI/s1600/terminal+start.jpghttp://3.bp.blogspot.com/-lF6ruaOQHC0/UGyWTq_1EXI/AAAAAAAAAh0/A48lWRxi5Q8/s1600/connector_03.jpghttp://3.bp.blogspot.com/-Ffd5jluyK8Y/UGyVcmhsL5I/AAAAAAAAAhs/YM9BE4o_898/s1600/decision_03.jpghttp://3.bp.blogspot.com/-WxJxEWb6kog/UGyUKDim_3I/AAAAAAAAAhk/tIFW7IKLdHg/s1600/arrows_03.jpghttp://2.bp.blogspot.com/-_9v1CN97nDg/UGyS39rrvrI/AAAAAAAAAhc/Hp_-6eIbRIg/s1600/process_03.jpghttp://3.bp.blogspot.com/-Yid4V_bSR_c/UGyRqbo5VJI/AAAAAAAAAhU/whLrCtdgJ64/s1600/output-input_03.jpghttp://3.bp.blogspot.com/-b6TQd1_QrPw/UGyQt8YViLI/AAAAAAAAAhM/eYSjwtZ_rsI/s1600/terminal+start.jpghttp://3.bp.blogspot.com/-lF6ruaOQHC0/UGyWTq_1EXI/AAAAAAAAAh0/A48lWRxi5Q8/s1600/connector_03.jpghttp://3.bp.blogspot.com/-Ffd5jluyK8Y/UGyVcmhsL5I/AAAAAAAAAhs/YM9BE4o_898/s1600/decision_03.jpghttp://3.bp.blogspot.com/-WxJxEWb6kog/UGyUKDim_3I/AAAAAAAAAhk/tIFW7IKLdHg/s1600/arrows_03.jpghttp://2.bp.blogspot.com/-_9v1CN97nDg/UGyS39rrvrI/AAAAAAAAAhc/Hp_-6eIbRIg/s1600/process_03.jpghttp://3.bp.blogspot.com/-Yid4V_bSR_c/UGyRqbo5VJI/AAAAAAAAAhU/whLrCtdgJ64/s1600/output-input_03.jpghttp://3.bp.blogspot.com/-b6TQd1_QrPw/UGyQt8YViLI/AAAAAAAAAhM/eYSjwtZ_rsI/s1600/terminal+start.jpghttp://3.bp.blogspot.com/-lF6ruaOQHC0/UGyWTq_1EXI/AAAAAAAAAh0/A48lWRxi5Q8/s1600/connector_03.jpghttp://3.bp.blogspot.com/-Ffd5jluyK8Y/UGyVcmhsL5I/AAAAAAAAAhs/YM9BE4o_898/s1600/decision_03.jpghttp://3.bp.blogspot.com/-WxJxEWb6kog/UGyUKDim_3I/AAAAAAAAAhk/tIFW7IKLdHg/s1600/arrows_03.jpghttp://2.bp.blogspot.com/-_9v1CN97nDg/UGyS39rrvrI/AAAAAAAAAhc/Hp_-6eIbRIg/s1600/process_03.jpghttp://3.bp.blogspot.com/-Yid4V_bSR_c/UGyRqbo5VJI/AAAAAAAAAhU/whLrCtdgJ64/s1600/output-input_03.jpghttp://3.bp.blogspot.com/-b6TQd1_QrPw/UGyQt8YViLI/AAAAAAAAAhM/eYSjwtZ_rsI/s1600/terminal+start.jpghttp://3.bp.blogspot.com/-lF6ruaOQHC0/UGyWTq_1EXI/AAAAAAAAAh0/A48lWRxi5Q8/s1600/connector_03.jpghttp://3.bp.blogspot.com/-Ffd5jluyK8Y/UGyVcmhsL5I/AAAAAAAAAhs/YM9BE4o_898/s1600/decision_03.jpghttp://3.bp.blogspot.com/-WxJxEWb6kog/UGyUKDim_3I/AAAAAAAAAhk/tIFW7IKLdHg/s1600/arrows_03.jpghttp://2.bp.blogspot.com/-_9v1CN97nDg/UGyS39rrvrI/AAAAAAAAAhc/Hp_-6eIbRIg/s1600/process_03.jpghttp://3.bp.blogspot.com/-Yid4V_bSR_c/UGyRqbo5VJI/AAAAAAAAAhU/whLrCtdgJ64/s1600/output-input_03.jpghttp://3.bp.blogspot.com/-b6TQd1_QrPw/UGyQt8YViLI/AAAAAAAAAhM/eYSjwtZ_rsI/s1600/terminal+start.jpg


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Sample Flowcharts


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1.6. PROCEDURAL PROGRAMMING

structured programming

a programming technique that splits the program into smaller segments(modules) to decrease program development time

decrease program maintenance cost

improve the quality of software

structured programming achieves these goals by using top-downdesign and use of modules

use of limited control structures (sequence, selection and repetition)

management control

Modular ProgrammingModular programming (also called "top-down design" and "stepwise refinement") is a software

design technique that emphasizes separating the functionality of a program into independent,

interchangeable modules, such that each contains everything necessary to execute only one

aspect of the desired functionality.

Conceptually, modules represent a separation of concerns, and improve maintainability by

enforcing logical boundaries between components. Modules are typically incorporated into the

program through interfaces.

Compiler

A compiler is a piece of code that translates the high level language into machine

language. When a user writes a code in a high level language such as Java and wants it to

execute, a specific compiler which is designed for Java is used before it will be executed.

The compiler scans the entire program first and then translates it into machine code

which will be executed by the computer processor and the corresponding tasks will be

performed.


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Shown in the figure is basic outline of the compilation process, here program written in

higher level language is known as source program and the converted one is called object

program.

Interpreter

Interpreters are not much different than compilers. They also convert the high level

language into machine readable binary equivalents. Each time when an interpreter gets ahigh level language code to be executed, it converts the code into an intermediate code

before converting it into the machine code. Each part of the code is interpreted and then

execute separately in a sequence and an error is found in a part of the code it will stop the

interpretation of the code without translating the next set of the codes.

Outlining the basic working of the interpreter the above figure shows that first a source

code is converted to an intermediate form and then that is executed by the interpreter.

The main differences between compiler and interpreter are listed below:

The interpreter takes one statement then translates it and executes it and then takesanother statement. While the compiler translates the entire program in one go and then

executes it.

Compiler generates the error report after the translation of the entire page while an

interpreter will stop the translation after it gets the first error.


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Compiler takes a larger amount of time in analyzing and processing the high level

language code comparatively interpreter takes lesser time in the same process.

Besides the processing and analyzing time the overall execution time of a code is

faster for compiler relative to the interpreter.

PROGRAM EXECUTION:

Step By Step Execution Of C Program

Step 1 : Edit

1. This is First Step i.e Creating and Editing Program.

2. First Write C Program using Text Editor , such as [ TurboC]

3. Save Program by using [.C] Extension.

4. File Saved with [.C] extension is called Source Program.

Step 2 : Compiling

1. Compiling C Program : C Source code with [.C] Extension is given as input to compiler and

compiler convert it into Equivalent Machine Instruction.

2. In Borland C/C++ 3.0 program can be compiled using key [Alt + F9 ].

3. Compiler Checks for errors. If source code is error-free then Code is converted into Object

File [.Obj ].

Step 3 : Checking Errors

1. During Compilation Compiler will check for error, If compiler finds any error then it will

report it.

2. User have to re-edit the program.

3. After re-editing program , Compiler again check for any error.

4. If program is error-free then program is linked with appropriate libraries.

Step 4 : Linking Libraries

1. Program is linked with included header files.

2. Program is linked with other libraries.

3. This process is executed by Linker.

Step 5 : Error Checking

1. If run time error occurs then Run-time errors are reported to user.

2. Again programmer have to review codeand check for the solution.


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Program execution steps


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Program compilation:

Compilation refers to the processing of Source code files(.c,.cc,.cpp) and the creation of an

object file.The compiler merely produces the machine language instructions that corresponds to

the source code file that was compiled.

The C Compilation Model:

The Preprocessor

The Preprocessor accepts source code as input and is responsible for

removing comments

interpreting special preprocessor dir ectivesdenoted by #.

For example

#include -- includes contents of a named file. Files usually called headerfiles. e.g


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o #include -- standard library maths file.

o #include -- standard library I/O file

C Compiler

The C compiler translates source to assembly code. The source code is received from the

preprocessor.

Assembler

The assembler creates object code. On a UNIX system you may see files with a .o suffix (.OBJ

on MSDOS) to indicate object code files.

Link Editor

If a source file references library functions or functions defined in other source files the l inkeditorcombines these functions (with main()) to create an executable file. External Variable

references resolved here also.

COMPARISION OF TESTING & DEBUGGING:

TESTING DEBUGGING

Program testing is the process

of checking program, to verifythat it satisfies its

requirements and to detect

errors.

Debugging is a methodical

process of finding andreducing the number of bugs

in a computer program making

it behave as expected.

Testing include necessarysteps to detect all possible

errors in the program.

One simple way to find thelocation of the error is to use

print statement to display the

values of the variables.

Testing is conducted by thetesters in testing phase.

Debugging done in thedevelopment phase by the

developers.

In testing phase tester will

finds the bug (i.e)called

testing to improve the quality

of the product

in development phase

developer fixes the bug

(i.e)called debugging

Finding and locating of defect. Fixing the defect.

Intension behind to find as

many defect as possible.

Intension is to remove those

defects.

Engineering CP unit I

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