Computer - Quick Guide


Computer - Overview

Today's world is an information-rich world and it has become a necessity for everyone to know about computers. Purpose of this tutorial is to introduce you about computer systems and its fundamentals.

Functionalities of a computer

Any digital computer carries out five functions in gross terms:

  • Takes data as input.

  • Stores the data/instructions in its memory and can use them when required.

  • Process the data and convert it into useful information.

  • Output the information.

  • Control all the above four steps.



Computer System is an electronic data processing device, which does the following:

  • Accept and store an input data.

  • Process the data input.

  • And output the processed data in required format.


Following list demonstrates the advantages of Computers in today's arena:

  • Computer is a very fast device.

  • In addition to being very fast, computers are very accurate.

  • The computer has performed calculations 100% error-free.

  • Computers perform all jobs with 100% accuracy.

  • The computer has much more storage capacity than human beings.

  • Unlike human beings, a computer is free from monotony, tiredness and lack of concentration.

  • It can work continuously without creating any error and boredom.

  • It can do repeated work with same speed and accuracy.

  • A computer is a very versatile machine.

  • A computer is very flexible in performing the jobs to be done.

  • Computer is an automatic machine.

  • The use of computers for data processing in an organization leads to reduction in paperwork and speeds up the process.

  • As data in electronic files can be retrieved as and when required, the problem of maintenance of large number of files gets reduced.

  • Though the initial investment for installing a computer is high but it substantially reduces the cost of each of its transaction.


Following list demonstrates the disadvantages of Computers in today's arena:

  • A computer is a machine and has no intelligence of its own to perform any task.

  • Each and every instruction has to be given to computer.

  • A computer can not take any decision on its own.

  • It can perform functions as instructed by user. So it is fully dependent on human being.

  • The operating environment of computer should be dust-free and suitable to it.

  • Computer has no feeling or emotions.

  • It cannot make judgement based on feeling, taste, experience and knowledge unlike a human being.

Computer - Applications

Following list demonstrates the various applications of Computers in today's arena.


The computer's characteristic as high speed of calculation, diligence, accuracy, reliability, or versatility has made it an integrated part in all business organisations.


Today, Banking is almost totally dependent on computers.


Insurance companies are keeping all records up-to-date with the help of computers. The Insurance Companies, Finance houses and Stock broking firms are widely using computers for their concerns.


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


With computers, advertising professionals create art and graphics, write and revise copy, and print and disseminate ads with the goal of selling more products.

Health Care

Computers have become important part in all Medical Systems.

Engineering Design

Computers are widely used in Engineering purposes.


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


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.

Government Applications

Computers play an important role in government applications like sales tax department, income tax department and computerization of voters lists, etc.

Computer - Generations

Generation in computer terminology is a change in technology a computer is/was being used. Initially, the generation term was used to distinguish between varying hardware technologies, but nowadays, generation includes both hardware and software, which together make up an entire computer system.

There are totally five computer generations known till date. Each generation has been discussed in detail along with their time period, characteristics. We've used approximate dates against each generations which are normally accepted.

Following are the main five generations of computers:

S.N.Generation & Description
1First Generation
The period of first generation: 1946-1959. Vacuum tube based.
2Second Generation
The period of second generation: 1959-1965. Transistor based.
3Third Generation
The period of third generation: 1965-1971. Integrated Circuit based.
4Fourth Generation
The period of fourth generation: 1971-1980. VLSI microprocessor based.
5Fifth Generation
The period of fifth generation: 1980-onwards. ULSI microprocessor based

Computer - Types

Computers can be broadly classified by their speed and computing power.

Sr. No.TypeSpecifications
1PC (Personal Computer)Single user computer system. Moderately powerful microprocessor.
2WorkStationSingle user computer system. Similar to Personal Computer but have more powerful microprocessor.
3Mini ComputerMulti-user computer system. Capable of supporting hundreds of users simultaneously.
4Main FrameMulti-user computer system. Capable of supporting hundreds of users simultaneously. Software technology is different from minicomputer.
5SupercomputerAn extremely fast computer which can perform hundreds of millions of instructions per second.

Computer - Components

All types of computers follow a same basic logical structure and perform the following five basic operations for converting raw input data into information useful to their users

Sr. No.OperationDescription
1Take InputThe process of entering data and instructions into the computer system.
2Store Data Saving data and instructions so that they are available for processing as and when required.
3Processing Data Performing arithmetic, logical operations on data in order to convert them into useful information.
4Output Information The process of producing useful information or results for the user,such as a printed report or visual display.
5Control the workflow Direct the manner and sequence in which all of the above operations are performed.
computer architecture

Input Unit

This unit contains devices with the help of which we enter data into computer. This unit makes link between user and computer.

The input devices translate the human being information into the form understandable by computer.

CPU (Central Processing Unit)

CPU is considered as the brain of the computer. CPU perform all types of data processing operations. It stores data, intermediate results and instructions (program). It controls the operation of all parts of computer.

CPU itself has following three components:

  • ALU (Arithmetic Logic Unit)

  • Memory Unit

  • Control Unit

Output Unit

Output unit consists of devices with the help of which we get the information from computer. This unit is a link between computer and users.

Output devices translate the computer's output into the form understandable by users.

Computer - CPU

  • CPU is considered as the brain of the computer.

  • CPU performs all types of data processing operations.

  • It stores data, intermediate results and instructions (program).

  • It controls the operation of all parts of computer.


CPU itself has the following three components.

  • Memory Or Storage Unit:

  • Control Unit

  • ALU (Arithmetic Logic Unit)


Memory Or Storage Unit:

This unit can store instructions, data and intermediate results. This unit supplies information to the other units of the computer when needed. It is also known as internal storage unit or main memory or primary storage or Random access memory (RAM).

Its size affects speed, power and capability. There are two types of memories in the computer: Primary memory and secondary memory. Functions of Memory Unit are:

  • It stores all the data to be processed and the instructions required for processing.

  • It stores intermediate results of processing.

  • It stores final results of processing before these results are released to an output device.

  • All inputs and outputs are transmitted through main memory.

Control Unit

This unit controls the operations of all parts of computer. It does not carry out any actual data processing operations.

Functions of this unit are:

  • It is responsible for controlling the transfer of data and instructions among other units of a computer.

  • It manages and coordinates all the units of the computer.

  • It obtains the instructions from the memory, interprets them and directs the operation of the computer.

  • It communicates with Input/Output devices for transfer of data or results from storage.

  • It does not process or store data.

ALU (Arithmetic Logic Unit)

This unit consists of two subsections namely:

  • Arithmetic section

  • Logic Section

Arithmetic section

Function of Arithmetic section is to perform arithmetic operations like addition, subtraction, multiplication and division. All complex operations are done by making repetitive use of above operations.

Logic Section

Function of logic section is to perform logic operations such as comparing, selecting, matching and merging of data.

Computer - Input Devices

Following are few of the important input devices, which are used in Computer Systems

  • Keyboard

  • Mouse

  • Joystick

  • Light pen

  • Track Ball

  • Scanner

  • Graphic Tablet

  • Microphone

  • Magnetic Ink Card Reader (MICR)

  • Optical Character Reader (OCR)

  • Bar Code Reader

  • Optical Mark Reader

Computer - Output Devices

Following are few of the important output devices, which are used in Computer Systems:

  • Monitors

  • Graphic Plotter

  • Printer

Computer - Memory

A memory is just like a human brain. It is used to store data and instruction. Computer memory is the storage space in computer where data to be processed and instructions required for processing are stored.

The memory is divided into large number of small parts. Each part is called cell. Each location or cell has a unique address, which varies from zero to memory size minus one.

For example, if computer has 64k words, then this memory unit has 64 * 1024 = 65536 memory location. The address of these locations varies from 0 to 65535.

Memory is primarily of three types:

  • Cache Memory

  • Primary Memory/Main Memory

  • Secondary Memory

Computer - RAM

A RAM constitutes the internal memory of the CPU for storing data, program and program result. It is read/write memory. It is called random access memory (RAM).

Since access time in RAM is independent of the address to the word that is, each storage location inside the memory is as easy to reach as other location & takes the same amount of time. We can reach into the memory at random & extremely fast but can also be quite expensive.

RAM is volatile, i.e., data stored in it is lost when we switch off the computer or if there is a power failure. Hence, a backup uninterruptible power system (UPS) is often used with computers. RAM is small , both in terms of its physical size and in the amount of data it can hold.

RAM is of two types:

  • Static RAM (SRAM)

  • Dynamic RAM (DRAM)

Primary Memory

Computer - ROM

ROM stands for Read Only Memory. The memory from which we can only read but cannot write on it. This type of memory is non-volatile. The information is stored permanently in such memories during manufacture.

A ROM stores such instructions as are required to start computer when electricity is first turned on, this operation is referred to as bootstrap. ROM chip are not only used in the computer but also in other electronic items like washing machine and microwave oven.


Computer - Motherboard

The motherboard serves as a single platform to connect all of the parts of a computer together. A motherboard connects CPU, memory, hard drives, optical drives, video card, sound card and other ports and expansion cards directly or via cables. It can be considered as the backbone of a computer.

Mother Board


  • Motherboard varies greatly in supporting various types of components.

  • Normally, a motherboard supports a single type of CPU and few types of memories.

  • Video Cards, Hard disks, Sound Cards have to compatible with motherboard to function properly.

  • Motherboards, cases and power supplies must be compatible to work properly together.

Computer - Memory Units

  • It is the amount of data that can be stored in the storage unit.

  • The storage capacity are expressed in terms of Bytes.

Following are the main memory storage units:

Sr. No.UnitDescription
1Bit (Binary Digit)A binary digit is logical 0 & 1 representing a passive or an active state of a component in an electric circuit.
2NibbleA group of 4 bits is called nibble.
3ByteA group of 8 bits is called byte. A byte is the smallest unit, which can represent a data item or a character.
4WordA computer word like a byte, is a group of fixed number of bits processed as a unit which varies from computer to computer but is fixed for each computer.
The length of a computer word is called word-size or word length and it may be as small as 8 bits or may be as long as 96 bits.
A computer stores the information in the form of the computer words.

Computer - Ports

  • A computer port is a physical docking point using which an external device can be connected to the computer.

  • A computer port can also be programmatic docking point through which information flows from a program to computer or over the internet.


  • External devices are connected to a computer using cables and ports.

  • Ports are slots on the motherboard into which a cable of external device is plugged in.

  • Examples of external devices attached via ports are mouse, keyboard, monitor, microphone, speakers, etc.


Computer - Hardware

Hardware represents the physical and tangible components of the computer, i.e., the components that can be seen and touched.

Examples of Hardware are following.

  • Input devices -- Keyboard, mouse, etc.

  • Output devices -- Printer, monitor, etc.

  • Secondary storage devices -- Hard disk, CD, DVD, etc.

  • Internal components -- CPU, motherboard, RAM, etc.

Computer Hardware

Computer - Software

Software is a set of programs which is designed to perform a well-defined function. A program is a sequence of instructions written to solve a particular problem.

There are two types of softwares:

  • System Software

  • Application Software

System Software

The system software is collection of programs designed to operate, control and extend the processing capabilities of the computer itself. System softwares are generally prepared by computer manufacturers.

These softwares comprise of programs written in low-level languages, which interact with the hardware at a very basic level. System software serves as the interface between hardware and the end users.

Some examples of system software are Operating System, Compilers, Interpreter, Assemblers, etc.

System Software

Application Software

Application software are the software that are designed to satisfy a particular need of a particular environment. All softwares prepared by us in the computer lab can come under the category of Application software.

Application software may consist of a single program, such as a Microsoft's notepad for writing and editing simple text. It may also consist of a collection of programs, often called a software package, which work together to accomplish a task, such as a spreadsheet package.

System Software

Computer - Data & information

What is Data?

Data can be defined as a representation of facts, concepts or instruction in a formalized manner, which should be suitable for communication, interpretation or processing by human or electronic machine.

Data is represented with the help of characters like alphabets (A-Z, a-z), digits (0-9) or special characters(+,-,/,*,<,>,=, etc.).

Computer Data

What is Information?

Information is organised or classified data so that it has some meaningful values to the receiver.

Information is the processed data on which decisions and actions are based.

For the decision to be meaningful, the processed data must qualify for the following characteristics:

  • Timely - Information should be available when required.

  • Accuracy - Information should be accurate.

  • Completeness - Information should be complete.

Computer Information

Computer - Networking

A computer network is a system in which multiple computers are connected to each other to share information and resources.

Computer Networks


  • Share Resources from one computer to another.

  • Create files and store them in one computer, access those files from the other computer(s) connected over the network.

  • Connect a printer, scanner, or a fax machine to one computer within the network and let other computers of the network use the machines available over network.

Computer - Operating System

  • An operating system is a program that acts as an interface between the software and the computer hardware.

  • It is an integration set of specialised programs that are used to manage overall resources and operations of the computer.

  • It is specialised software that controls and monitors the execution of all other programs that reside in the computer, including application programs and other system software.

Objectives of Operating System

  • Making a computer system convenient to use in an efficient manner.

  • To hide the details of the hardware resources from the users.

  • To provide users a convenient interface to use the computer system.

  • To act as an intermediary between the hardware and its users and making it easier for the users to access and use other resources.

  • Manage the resources of a computer system.

  • Keep track of who is using which resource, granting resource requests, according for resource using and mediating conflicting requests from different programs and users.

  • The efficient and fair sharing of resources among users and programs

Operating System

Computer - Internet & Intranet


  • Internet is a world-wide/global system of interconnected computer networks.

  • Internet uses the standard Internet Protocol (TCP/IP)

  • Every computer in internet is identified by a unique IP address.

  • IP Address is a unique set of numbers (such as which identifies a computer location.

  • A special computer DNS (Domain Name Server) is used to give name to the IP Address so that user can locate a computer by a name.

  • For example, a DNS server will resolve a name to a particular IP address to unique identify the computer on which this website is hosted.

  • Internet is accessible to every user all over the world.



  • Intranet is system in which multiple PCs are networked to be connected to each other.

  • PCs in intranet are not available to the world outside of the intranet.

  • Usually, each company or organization has its own Intranet network and members/employees of that company can access the computers in their intranet.

  • Each computer in Intranet is also identified by a IP Address, which is unique among the computers in that Intranet.