Computer is an advanced electronic device that performs both numerical (arithmetic) and non-numerical (logical) operations.

  • These operations are helpful in large scale as well as in small-scale industries which in the past were handledby humans.
  • In recent days it is also used in homes, where they are used for things such as browsing information through the internet, listening to music and lot more.
  • This device takes raw data as input and by processing these data under the control of the set of instructions (program) it gives the result (output). We can also save these outputs for future reference.

A computer has four basic functions; they are as input, processing, output and storage which do the below activities:


Input - where the raw information is entered into a computer with help of an input device. This information can be in form of a collection of letters, numbers, images etc.

Process - it is the sequence of operation of any given data as per the instruction.

Output - these are the results which are generated by data processing.

Storage - We can save these results in the storage devices for future reference.

Computer System

The components of a computer can be simplified as shown below:


  • There are three major components of a computer system. Each of the components works hand in hand.
  • Hardware is the Infernal Devices and Peripheral Devices, which are usually the physical parts of the computers that can be touched.
  • The software is the Programs which gives the set of guidelines for the computer to function.
  • The user is the end user, mostly a human who operates the computer.


Generations of computer


First Generation (1940-56):

  • The first generation computers were large in size and programming were a difficult task.
  • These computers used vacuum tubes and machine language for giving the set of instructions.
  • The electricity consumption was also very high.
  • Few of first generation computers: ENIAC, EDVAC, EDSAC & UNIVAC-1.

Second Generation (1956-63):

  • In second generation computers, transistors replaced the vacuum tubes.
  • They required only 1/10 of power compared to the ones by tubes.
  • These computers generated less heat and were also reliable.
  • The first operating system was developed in that generation.

The Third Generation (1964-71):

  • The third generation computers were introduced with an Integrated circuit known as a chip.
  • The technology developed to MSI circuits with 100 transistors per chip from a small integrated circuit which had 10 transistors per chip.
  • These computers were smaller, faster & more reliable.
  • High-level languages were invented in this generation.

The fourth Generation (1972- present):

  • The fourth generation used LSI & VLSI.
  • This brought microprocessors into existence.
  • The computers using this technology are known to be Micro Computers.
  • High capacity hard disk was invented which brought great development in data communication.

The Fifth Generation (Present & Beyond):

  • Fifth generation computing devices are based on artificial intelligence
  • These have the latest applications, such as voice recognition, that is being used today.
  • The use of parallel processing and superconductors is helping to make artificial intelligence a reality. 

Architecture of computer

  • Input Devices: these are devices with which the data is entered by the user into the computer system. Eg. Keyboard, Mouse, Touchscreen, Barcode Reader, Scanner, etc.
  • Output Devices: these devices are like the screen which helps by displaying the processed information. Eg. Monitor, Printer, Plotter, Projector
  • CENTRAL PROCESSING UNIT (CPU) - The CPU (Central Processing Unit) is the device that interprets and executes instructions. It performs arithmetic and logic operations.
  • The main component that makes a computer operator is the computer chip or microprocessor.
  • This is referred to as the Central Processing Unit (CPU) which is housed in the computer case. Together, they are also called the CPU. 


  • It is the storage device that facilitates the remembrance power to the computer system.
  • It refers to the physical devices used to store programs (sequences of instructions) or data on a temporary or permanent media in a computer.
  • Any information stored in the computer systems that are fast (i.e. RAM) is the primary memory.
  • Secondary memory is a physical device for program and data storage which are slow to access but offer higher memory capacity.
  • Primary memory stored on secondary memory is called virtual memory.
  • Primary Memory can be categorized as Volatile Memory & Non-Volatile Memory.

Volatile memory (RAM): Volatile memory requires power to maintain the stored information. Most modern semiconductor volatile memory is either Static RAM or dynamic RAM.

Static RAM: until it is connected to the power supply it retains the contents and is easy to interface too but uses six transistors per bit.
Dynamic RAM – complicated to interface to and control and also needs a regular refresh cycle to prevent the contents being lost.

Non Volatile Memory (ROM): Non-volatile memory is computer memory that can retain the stored information even when not connected to power supply. Examples of non-volatile memory are the flash memory and ROM/PROM/EPROM/EEPROM memory (used for firmware such as boot programs).

Cache Memory: It is an auxiliary memory, from which high-speed retrieval is possible.

Types of Computer

Computers are of various types based on their working principle and also the size of the device.

On the basis of the working principle we have the following:
a) Analog Computer – These are forms of a 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 – They perform operations with quantities represented as digits, which are usually in the binary number system that includes 0 and 1. These performances are both calculation and logical operations.

c) Hybrid Computer (Analog + Digital) – A combination of computers those accept input and output in both digital and analog signals. A hybrid computer system is used in the medical science industry as it is expensive and also it performs complex simulations.

On the basis of the size we have the following:

a) Super Computer - Expensive and the fastest type of computer.Used in applications that require immense amounts of mathematical calculations. For example, weather forecasting requires a supercomputer.

b) MainframeComputer - A large and expensive computer capable of supporting thousands, of users simultaneously. They support more simultaneous programs hence superior than a supercomputer. But supercomputers can execute a single program faster than a mainframe.

c) Mini Computer - A midsized computer. Minicomputers lie between workstations and mainframes, in size and power. Example - servers are listed in this category.

d) Micro Computer - 

Desktop Computer: A personal computer sufficient to fit on a desk.
Laptop Computer: A portable computer complete with an integrated screen and keyboard.

Notebook /PDAs: A hand-sized computer. No keyboard but the screen plays both as an input and output device.

e) Workstations - A terminal or desktop computer in a network.


It is the programs that run on a computer.

  • The set of instructions given to the computer in the form of a program is called Software.

  • The software is the set of programs, which are used for different purposes to perform a specific task.

    There are mainly two types of software, they are: System software and  Application software

System software - These are software that is designed to provide a platform for other software.

a) Operating System Software - examples are DOS, Windows XP, Unix/Linux, MAC/OS X etc.

b) Utility Software - examples are Windows Explorer (File/Folder Management), Compression Tool, Anti-Virus Utilities, Disk Clean, BackUp, WinZip, etc...

c) Language Processors - examples are Compiler, Interpreter and Assembler

Application software - These are designed to perform a group of functions, tasks, or activities for the benefit of the user.

a) Package Software - examples are Ms. Office 2003, Ms. Office 2007, Macromedia (Dreamweaver, Flash, Freehand), Adobe (PageMaker, PhotoShop)

b) Tailored or Custom Software such as School Management system, Inventory Management System, Payroll system, financial system etc.


A computer has four basic functions they are as input, processing, output and storage.

The components of a computer can be simplified as



Generations of computer

  • First Generation: vacuum tubes
  • Second Generation: transistors
  • Third Generation: Integrated circuit
  • The fourth Generation: microprocessors
  • The Fifth Generation: artificial intelligence


Architecture of computer

  • Input device - Eg. Keyboard, Mouse
  • Output device - Eg. Monitor, Printer
  • CPU - interprets and executes instructions


Memory - storage device that facilitates the remembrance power to a computer system.


Types of Computer

  • Computers are of various types based on their working principle and also the size of the device.