The Word Computer comes from the word “compute” which, means to calculate. But now days, computers are also being used for many other purposes else calculating.  

Thus the computer can be defined as:

It is an electronic device which accepts instructions in the form of input and after processing it gives us information in the form of output.”

Brief History of Computer

  1. In 17th Century BLAISE PASCAL a mathematician and scientist of France developed the first mechanical calculator, which he called the “Pascalins”.
  2. CHARLES BABBAGE a mathematician of UK in 1822 designed a special type of calculator called “difference Engine” and in 1833 he developed a machine called “ANALYTICAL ENGINE”.
  1. Later on American Scientists Working at Howard University developed a computer between 1937 and 1943 called “Howard Mark-I”.
  2. First electronic computer was developed in 1946 at the University of Pennsylvania USA.

First Personal computer (PC) was developed in 1981.

Classification of Computers

Computer is classified according to their size, Technology and the working principal into different categories.

  1. Depending upon size

2. Depending upon Working size

3. Depending upon Technology

Depending Upon Their Size:

Super Computer:

Fastest, Most Powerful, Most expensive, Large in size and Memory, Multi –User. The first Cray Super Computer was introduced in 1976.

Mainframe Computer:

Less powerful than Super Computer, Large in size and memory, Multi –user, Expensive.

Mini Computers:

Less powerful than Mainframe, Medium Sized, Multi-user, Expensive.

Personal computer


Single user, Powerful Enough, In expensive, Personal Computer

Depending upon their working Principle

(a) Analog Computer:

 Such a type of computer in which input is given in the form of digits but the output is receiving in graphical form. This output is correct 90% to 95% (i.e. Wall Clock, Thermometer, Magnetic Needle etc.)

(b) Digital Computer

Digital computer that in which input is given in the form of digits and output is also received in form of digits (Digital Watch, Calculator etc.)

(c) Hybrid Computer

These computers have both properties analog and digital. Hybrid Computer given output in both digits and graphs all PC are the Hybrid computers having both properties.

Introduction to Personal Computers

Personal computer is also called Microcomputer. Microcomputer was designed to be one person at a time. These are small in size and mainly used in Accounting, Database, Word Processing and Spread Sheet packages etc.

Intel-Based microcomputer is of two categories; Old Series:          8088, 8086, 80286, 80386, 80486 and 80586

New Series:        Pentium I, Pentium II Pentium III, Celeron, Pentium 4, Pentium Core.

Branded Computer:

These computers are assemble or manufactured a company and marketed them with a special name.  For example IBM, APPLE, ACER, COMPAQ, HEWLLETT PACKARD (HP), DELL and so on. These are high quality, high cost machines.

NON-Branded Computer:

These computers have no special name but these recognize with its technology like Pentium 1 or Pentium 4. They are normally assembled with different companies parts. They are cheap and less reliable machines.

PC’s normally come in four sizes & Shapes;

  • Desk Top PC
  • Tower PC
  • Laptop PC
  • Palm Top PC


Everything that we give to the computer system through input devices is called input.

Input Devices

An input device is any hardware component that allows you to enter data or instruction into a computer. Most commonly used input devices are the keyboard, mouse, microphone, scanner, digital camera, and PC video camera.

1KEYBOARD Computer keyboards are similar to electric-typewriter keyboards but contain additional keys. Keyboard is use to enter data into a computer.2MOUSE A device that controls the movement of the cursor or pointer on a display screen.
3Track Ball A trackball is a specific style of computer mouse. User track the ball with his finger and arrow move the on-screen.4GLIDE PAD A Glide Pad, also called touchpad, track pad is a pointing device consisting of specialized surface that can translate the motion and position of a user’s fingers to a relative position on screen.
5SCANNER Scanners or computer scanners are used to transfer images or text into a computer.6MICROPHONE A microphone used to converts voice or sound into an electrical signal.
7  DIGITAL CAMERA A digital camera is a camera that takes video or still photographs.8WEB CAM A webcam is a video camera which feeds its images in real time to a computer
9BARCODE READER A barcode reader (or barcode scanner) is an electronic device for reading printed barcodes.10JOY STICK A lever that moves in all directions and controls the movement of a pointer. It use for play Games.


Multimedia is a combination of sound and images with text and graphics. This would include movies, animation, music, people talking, sound effects like the roar of a crowd, smashingetc.


Everything that computer display after processing is called output.

Types of Output:-

1: Hard Form: Printed paper or other permanent media that physically exists.

2: Soft Form: Displayed on screen or by other non-permanent means that not keep physically.

OUTPUT DEVICES Computer hardware components that are used to receive processed information from

computer are called output devices.

1Monitor / LCDA monitor or display (sometimes called a visual display unit) is an electronic visual display for computers. It’s like TV
2SpeakersA loudspeaker (or “speaker”) that produces sound in response to an electrical audio signal input.
3PrintersIt takes electrical signals from computer and convert them in to text and make an image on paper.
4PlottersA plotter is a computer printing device for printing Big level graphics.
5ProjectorAn LCD projector is a type of video projector for displaying video, images or computer data on a big screen.

Central Processing Unit (CPU)

The Microprocessor, also called the central processing unit, interprets and carries out all the basic instructions that operate the computer. (See Pictures 1.4)

Input Devices
Output Devices
Storage Devices
Central Processor Unit
Control Unit (CU)
Arithmetic & Logic Unit (ALU)

Processor contains a Control Unit (CU) and an Arithmetic and Logic Unit (ALU). These two components work together to perform processing of operations.

Control Unit (CU)

The control unit is the component of the processor that directs a coordinates most of operations in the computer. The control unit has a rule much like a traffic cops: it interprets each instruction issued by a program and then initiates the appropriate action to carry out the instructions.

Arithmetic Logic Unit (ALU)

The Arithmetic and Logic Unit (ALU) another component of the processor performs arithmetic, comparison, and logical operation. Arithmetic operations include basic calculation such as addition, subtraction, multiplication and division. Logical operation include conditions along with logical operator such as AND, OR, and NOT. For example, if only employees paid hourly can receive overtime pay, the ALU must verify to condition before computing an overtime wage:

  1. The employee is paid hourly AND.
  2. The employee worked more than 40 hours


The mother board sometime called a system board is the main circuit board of the system unit. It is used to connect all kind of hardware devices.

Ports: A ‘port’ serves as an interface between the computer and other computers or peripheral devices. Physically, a port is a specialized outlet on a piece of equipment to which a plug or cable connects.


Storage refers to the media either data are stored temporarily or permanently. There are two main types of storage.

Primary Storage or Main Memory

Secondary Storage

Primary Storage or Main Memory (RAM)

Primary storage, presently known as memory or simply RAM, is the only one directly accessible to the CPU. The CPU continuously reads instructions stored there and executes them as required. Any data actively operated on is also stored there in uniform manner. Memory stores three basic categories of data.

  • Operating system and other system software that control or maintain the computer and its devices
  • Application programs that carry out a specific task such as word processing etc.
  • Data to be processed by the application programs and resulting information.

RAM Stands for Random Access Memory.RAM is also called main memory

or primary storage, it consists of memory chips that can be read from and written to by the processor and other devices.RAM varies in size like 128 MB, 256 MB, and 512 MB to 2 GB.

RAM cannot store data and instruction permanently.

When we switch off the computer, all data and instructions from RAM are washed or vanished. Therefore it is called volatile memory.

ROM stands for Read only Memory. It consists of those instructions that prepare the computer for use. ROM instructions are automatically loaded into the Main Memory. These instructions can only be read but cannot be changed or deleted. It is not possible to write new instructions into the ROM. It stores data and instructions permanently. When we switch off the computer, the instructions stored in the ROM are not lost. Therefore it is called a non-volatile memory.


It has three types:

  • Magnetic Disk
  • Optical Disc
  • Flash Memory

Magnetic Disk

It is most widely used storage media for all type of computer. A magnetic disk is a thin circular metal plate or platter coated with magnetic material. Information can be record on or read from the magnetic surface through magnetism. Magnetic disk is a random access storage media.

Types of Magnetic Disk

There are the following types of the magnetic disk.

  1. Hard Disk
  2. Floppy Disk
  3. Zip Disk

Optical Disc

Optical disk issued laser technology to read or write information. LASER Stands for Light Amplification by Stimulated Emission of Radiation Laser beam is used to make tiny holes on the surface of the disk.

Compact Disc (CD)

CD is the most popular optical medium. It can hold 650 MB to 800 MB of data. The data on the CD cannot be erased like magnetic diskettes.


DVD, also known as “Digital Versatile Disc” or “Digital Video Disc“, is an optical disc storage media format. Its main uses are video and data storage. DVDs are of the same dimensions as compact discs (CDs), but store more than six times as much data.

Blu-Ray Disc

Blu-Ray Disc (official abbreviation BD) is an optical disc storage medium designed to supersede the DVD format. The standard physical medium is a 12 cm plastic optical disc, the same size as DVDs and CDs. Blu-Ray Discs contain 25 GB per layer, with dual layer discs (50 GB) the standard for feature-length video discs and additional layers possible in the future.

Flash memory and Drive

Flash memory is a non-volatile computer storage chip that can be electrically erased and re-programmed. It is primarily used in memory cards, USB flash drives, MP3 players and solid-state drives for general storage and transfer of data between computers and other digital products. It is a specific type of EEPROM (electrically erasable programmable read-only memory) that is erased and programmed in large blocks; in early flash the entire chip had to be erased at once.

USB Drive

A USB flash drive consists of a flash memory data storage device integrated with a USB (Universal Serial Bus) interface. USB flash drives are typically removable and rewritable, and physically much smaller than a floppy disk. Most weight less than 30g. Storage capacities in 2010 can be as large as 256 GB with steady improvements in size and price per capacity expected. (See Pictures 1.8)

What is Data?

A collection of facts and figures that we give to the computer for gathering useful results and information is called data. There is three types of data.

  • Alphabetic Data (A to Z)
  • Numeric Data (0 to 9)
  • Alphanumeric Data (A to Z and 0 to 9)

The Binary System

The binary system of numbers uses the base of 2 (0 and 1). A bit can exist in only two states, ON or OFF.

The Units of Storage

Memory UnitValue
BitSmallest unit of information, shorthand term for binary digit
Nibble4 bits (Half of a byte)
Byte8 bits (Equal to one character)
Word16 bits on most personal computers (longer words possible on larger computers)
Kilobyte (KB)1024 bytes
Megabyte (MB)1,048,576 bytes (Approximately one million bytes or 1024 KB)
Gigabyte (GB)1,073,741,824 bytes (Approximately one billion bytes or 1024 MB)
Terabyte (TB)1024 Gigabyte of data

What is Hertz?

In 1887 German physician Heinrich Hertz demonstrate the effects of electromagnetic radiation through space. In this honor the hertz (Hz) is now the standard unit for the measurement of the frequency (1 Hz equals one complete cycle per second)

Memory UnitValue
1000 Hertz1Kilo HertzKHZ
1000  Kilo Hertz1Mega HertzMHZ
1000 Mega Hertz1Giga HertzGHZ
1000 Giga Hertz1 Tera HertzTHZ
1000  Tera Hertz1 Peta HertzPHZ

Clock Speed:

The frequency of oscillations or clock cycle/sec. It is measured in hertz. Computers today operate in the range 100 MHZ to 3 GHZ and so on.

Power Safety Guidelines

The following are some general guidelines to follow when working around computers:

  • Never wear jewelry or other metal objects when working on a computer. These items pose an electrical threat that can cause shorts, which will destroy components.
  • To avoid spills, never use liquids around electrical equipment.
  • Replace any wrong or damaged power cords or extension immediately.
  • Never allow anything to rest on a power cord.
  • Avoid using extension cords that has lose sockets. These can cause by tripping hazards or short circuits.
  • Keep all electrical covers intact.
  • Make sure all vents are clear and have ample free-air space to allow heat to escape.
  • Some peripheral devices such as laser printers and scanners use high voltages. Before removing any covers or working on any of these devices, be sure to read the manufacturers’ manuals carefully.
  • Make sure the proper lighting and work area.


Fire is not pleasant to think about, but it is a fact of life. A workplace fire can be disastrous both in terms of lost equipment and injury to people. Knowing what to do in the event of a fire can save valuable equipment and, most importantly, lives. Here are a few tips to help prevent fire and protect yourself:

  • Always know the emergency procedures to be carried out in case of fire at your workplace.
  • Know the location of the nearest fire exits.
  • Know the location of the nearest fire extinguishers and how to use them.
  • Don’t overload electrical outlets.

Simply knowing the location of a fire extinguisher is of no value unless you know how to use it. If you don’t, contact your safety department or local fire department. They will be glad to help you get the training you need. Also, remember that using the wrong type of fire extinguisher can be worse than not using one at all.

By admin

2 thoughts on “What is Computer?”
  1. The following time I read a blog, I hope that it doesnt disappoint me as a lot as this one. I mean, I know it was my choice to learn, but I actually thought youd have something fascinating to say. All I hear is a bunch of whining about something that you possibly can fix if you werent too busy on the lookout for attention.

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