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What is Computer?

A computer is an electronic device that takes instructions from humans and converts that information to arithmetic or logical operations called machine language. A basic computer can store, process, and transfer data while an advanced machine makes predictions and decisions based on conditions and information it reads.

What is a Computer?

A computer is a programmable machine designed to perform arithmetic and logical operations automatically and sequentially on the input given by the user and gives the desired output after processing. Computer components are divided into two major categories namely hardware and software. Hardware is the machine itself and its connected devices such as a monitor, keyboard, mouse etc. The software is the set of programs that make use of hardware for performing various functions.

Types of Computer

There are three main kinds of computers.

1. Workstation Computer
2. Personal Computer or PC
3. Server Computer

Types of computers on the basis of application

Digital Computer

Analog Computer

Hybrid Computer

Characteristics of Computers

The characteristics of computers that have made them so powerful and universally useful are speed, accuracy, diligence, versatility and storage capacity. Let us discuss them briefly.

Speed: Computers work at an incredible speed. A powerful computer is capable of performing about 3-4 million simple instructions per second.

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).

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, are better than human beings in performing voluminous and repetitive jobs.

Versatility: Computers are versatile machines and are capable of performing any task as long as it can be broken down into a series of logical steps. The presence of computers can be seen in almost every sphere – Railway/Air reservation, Banks, Hotels, Weather forecasting and many more.

Storage Capacity: Today’s computers can store large volumes of data. A piece of information once recorded (or stored) in the computer, can never be forgotten and can be retrieved almost instantaneously.

Computer Organisation

A computer system consists of mainly four basic units; namely the input unit, the storage unit, the central processing unit and the output unit. Central Processing unit further includes Arithmetic logic unit and control unit. A computer performs five major operations or functions irrespective of its size and make. These are:

  • It accepts data or instructions as input
  • It stores data and instruction
  • It processes data as per the instructions
  • It controls all operations inside a computer, and
  • It gives results in the form of output.

Functional Units of Computer

Input Unit: This unit is used for entering data and programs into the computer system by the user for processing.

Storage Unit: The storage unit is used for storing data and instructions before and after processing.

Output Unit: The output unit is used for storing the result as output produced by the computer after processing.

Processing: The task of performing operations like arithmetic and logical operations is called processing. The Central Processing Unit (CPU) takes data and instructions from the storage unit and makes all sorts of calculations based on the instructions given and the type of data provided. It is then sent back to the storage unit. CPU includes Arithmetic logic unit (ALU) and control unit (CU).

Arithmetic Logic Unit: 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 etc.

Control Unit: Controlling all operations like input, processing and output are performed by the control unit. It takes care of step by step processing of all operations inside the computer.

Computer Memory

Computer’s memory can be classified into two types; primary memory and secondary memory.

Primary Memory

The computer primary memory is also known as main memory. The main memory is directly or indirectly connected to the central processing unit via a memory bus. The CPU continuously reads instructions stored there and executes them as required. It can be further classified as RAM, ROM, and Cache.

Random Access Memory (RAM)

RAM or Random Access Memory is the unit in a computer system. The RAM is a volatile memory having a limited storage capacity. 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 computer’s processor. It is said to be ‘volatile’ since its contents are accessible only as long as the computer is on. The contents of RAM are no more available once the computer is turned off.

There are two types of RAM: DRAM (Dynamic Random Access Memory) and SRAM (Static Random Access Memory)

Read Only Memory (ROM)

ROM or Read Only Memory is a special type of memory which can only be read and the contents of which are not lost even when the computer is switched off. It typically contains the manufacturer’s instructions. Among other things, ROM also stores an initial program called the ‘bootstrap loader’ whose function is to start the operation of a computer system once the power is turned on.


Computer Cache is a high-speed access area that can be either a reserved section of main memory or a storage device.

Secondary Memory

The computer secondary memory is not directly accessible by the CPU. The computer usually uses its input/output channels to access secondary storage and transfers the desired data using intermediate area in primary storage. These include devices that are peripheral and are connected and controlled by the computer to enable permanent storage of programs and data. Secondary storage devices are of two types; magnetic and optical. Magnetic devices include hard disks and optical storage devices are CDs, DVDs, Pen drive, Zip drive etc.

Hard Disk

The computer 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 is a permanent part of the computer where data and programs are saved.

Compact Disk

Compact Disk (CD) is a portable disk having data storage capacity between 650-700 MB. It can hold a large amount of information such as music, full-motion videos, and text etc. CDs can be either read-only or read-write type.

Digital Video Disk

Digital Video 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. DVDs are primarily used to store music or movies and can be played back on your television or the computer too. These are not rewritable.

Input / Output Devices

These devices are used to enter information and instructions into a computer for storage or processing and to deliver the processed data to a user. Input/Output devices are required for users to communicate with the computer. In simple terms, input devices bring information into the computer and output devices bring information OUT of a computer system. These input/output devices are also known as peripherals since they surround the CPU and memory of a computer system.

Examples of computer input devices: Keyboard, Mouse, Trackball, Touchpad, Touch Screen, Light Pen, Magnetic ink character recognition (MICR), Optical mark recognition (OMR), Barcode reader, Scanner etc.

Output Devices

The output device receives information from the CPU and presents it to the user in the desired form. 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 ways – on the display device, or on paper (hard copy).

Examples of computer output devices: Monitor Screen, Printer, Impact Printers, Non-impact printers, Plotter, Facsimile (FAX), Sound cards and Speaker(s) etc.

Computer Software

A computer software is the set of programs that make the hardware perform a set of tasks in particular order. Hardware and software are complementary to each other. Both have to work together to produce meaningful results. Computer software is classified into two broad categories; system software and application software.

Types of application software: Word processing software, Database software, Spreadsheet software, Presentation software, Multimedia software etc.

Computer Language

Computer language or programming language is a coded syntax used by computer programmers to communicate with a computer. Computer language establishes a flow of communication between software programs. The language enables a computer user to dictate what commands the computer must perform to process data. These languages can be classified into the following categories:

1. Machine language
2. Assembly language
3. High-level language

Compiler & Interpreter

These are the programs that execute instructions written in a high-level language. There are two ways to run programs written in a high-level language. The most common is to compile the program; the other method is to pass the program through an interpreter.

Open Source Software

The open source refers to a program or software in which the source code (the form of the program when a programmer writes a program in a particular programming language) is available to the general public for use and/or modification from its original design free of charge.

Operating System (OS)

An operating system is a software component of a computer system that is responsible for the management of various activities of the computer and the sharing of computer resources.

Computer Security

When data takes the shapes of digital form, a different security procedure is required. This branch of security is called computer security.

Computer Virus

A computer virus is a program which has been written to interfere with the normal functioning of the computer. It does this by clogging the memory of the system by making copies of itself or it may destroy critical information used by other computer programs.

Further Related Information

What is a Computer Keyboard? (Basic Information)

What is a Computer Monitor Screen (Basic Information)

Difference Between Digital and Analog Computer

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