What is Computer?

  • The term computer (PC) has been borrowed from compute that means- to calculate.
  • Whereas initially computers (PC) were used to perform arithmetic calculations at fast speed, now they are used in nearly every field of our day-to-day life.
  • A computer may be defined as a device that receives some kind of data, analyses it, and then applies a pre-defined set of instructions to it to produce some kind of output.
  • In short, computer is electronic device which can perform any task with high speed and accuracy.
  • The principal of computer is input->process->output.
  • For example: when you go to a railway ticket reservation counter, the operator feeds your request for a ticket reservation into the computer.
  • The computer (PC) then analyses the information (data) fed by the operator and makes a reservation.
  • Then it prints a ticket for you. The ticket is the output generated by the computer based on the reservation request enters by the operator.
  • It may be also said that the computer (PC) is a data processor, because it can receive, store, process and retrieve any kind of information (data).
  • For example: you can store the names and address of all the students of the college.Later, you can ask the computer to print a list of only those students coming from same city.

Computer Knowledge

Full form of Computer

  • C – Commonly
  • O – Operated
  • M – Machine
  • P – Particularly
  • U – Used for
  • T – Technical
  • E – Education
  • R – Research

Characteristics of Computer

  • Speed
  • Accuracy
  • Storage
  • Diligence
  • Versatility
  • Automation
  • No Feeling
  • Power Of Remembering
  • What is Computer?

    Computer: A Computer (PC) may be a General purpose machine, commonly consisting of digital circuitry, that accepts (inputs), stores, manipulates, and generates (outputs) information (data) as numbers, text, graphics, voice, video files, or electrical signals (wave), in accordance with instructions called a program.

    • Father of the computer – Charles Babbage.
    • Father of the modern computer – Alan Turing.
    • Basic Architecture of Computer: John Von Neumann (1947-49).
    • First Programmer: Lady Ada Lovelace (1880).
    • First Electronic Computer: ENIAC (1946) – J.P. Eckert & J.W. Mauchly.
    • The first computer for the home user introduced – IBM (International Business Machines) in 1981.
  • Computer – Basic Things
    • A computer may be a device which will receive process and store data.
    • However, all computers have several parts in common:
    • Input devices allow data and commands to the computer (Printer,Mouse, Keyboard etc.)
    • Memory for storing commands and data.
    • Central Processing Unit which controls the processing.
    • Monitor Process the knowledge within the sort of output.
  • Block Diagram of Computer
    • Computer perform basically five major operation or function
    1. It accepts information (data) or instruction by way of input.
    2. It store data.
    3. It can process data as needed by the user.
    4. It give result in the form of output.
    5. It controls all operation inside a computer.

    Input Unit

    • The processing of data into computer is known as
    • Input devices are keyboard, mouse, floppy disk, hard disk and magnetic tape.
    • Input device perform the following function.
    1. Accept data and instruction from the outside world.
    2. Convert it to a form that the computer (PC) can understand.
    3. Supply the converted data to the computer system for the further processing.

    Storage unit

    • The process of saving data and instruction permanently is known as Storage unit
    • The various storage devices used in computer system are classified into two categories-primary and secondary.

    Primary storage

    • Primary storage also called primary memory, stores and provides information (data) very fast.
    • The primary generally loses its information (data) when user switches off computer.
    • The cost of the primary storage is more compare to secondary storage.

    Secondary Storage

    • It may store several programs, documents, database etc.
    • The secondary storage slower (low) and cheaper than primary storage.
    • It save its information (data) after the computer is switch off.


    • This is process of producing result from the information (data) for getting useful information (data).
    • Output device are monitor and printer


    • The CPU or processor is the brain of the computer (PC).
    • It is the main device which executes an instruction.


    • The task of performing output like arithmetic and logical operation is named (called) processing.


    • It takes care of step by step processing of all operations inside the computer (PC).
  • Generations of Computers

    1st Generation(1940-1956)

    • The early electronic computers, such as ENIAC, EDSAC, EDVAC, UNIVAC I etc. are first generation computers.
    • They used vacuum tubes to control the flow of electronic signals (wave).
    • These computers used thousands of vacuum tubes.
    • Vacuum tubes are big in size (about the size of a small electric lamp) and produce a lot of heat.
    • Because of this, the first generation computers were too bulky in size and used to produce a lot of heat.
    • The vacuum tubes used to burn out frequently resulting in failure of the computer (PC).
    • Therefore, these computers (PC) could not be used continuously and had to be stopped frequently.
    • They were programmed using machine language

    2nd Generation(1956-1963)

    • They were introduced around 1959.
    • These were made of transistors.
    • Transistors are a smaller and more reliable component invented in 1947.
    • A transistor (one type of small chips) is very small compared to the vacuum tube and produces very little heat.
    • The use of transistors in computers made the second generation computers faster, smaller and reliable.
    • Assembly language introduced. This language is easy (basic) to write program than machine language.

    3rd Generation(1964-1971)

    • The introduction of integrated circuits (ICs), also known as chips, opened the door for the development of the third generation computers.
    • A very large number (sizable amount) of circuit elements – transistors, diodes, resistors, etc. could be integrated into a really small surface of silicon.
    • These were based on IC technology.
    • The System/360 introduced by IBM in 1964 was the first third generation computer (PC).
    • They were smaller, faster and more reliable than second-generation computers (PC).
    • Many input/output devices were introduced like mouse and keyboard.

    4th Generation(1971-Present)

    • This computer is based on LSI chips.
    • Because of the very small size of the ICs used in (utilized in) these computers, they’re very small, very powerful, fast and cheap.
    • This is why an ordinary person can own a computer.
    • Use advance input and output devices like optical readers,laser printrs,cd-roms/dvd-rom driver.

    5th Generation(Present and Beyond)

    • Scientists are working on the development of fifth-generation computers.
    • They will have intelligence, ability to reason and learn knowledge of the important world.
    • They will understand and talk in natural language.

    Features of this computer :

    1. Having their own thinking power
    2. Making decisions themselves.
    3. Having capabilities of reasoning
    4. Having large capacity of internal storage
    5. Having extra high processing speed
    6. Having capabilities of parallel processing
  • Types of Computer
    • Computers (PC) can be classified based on information (data) processing speed,amount of data that they can hold(size), application, technology etc.
    • Generally,a computer (PC) with high processing speed and large internal storage is called a big computer (PC).
    • Depending upon their speed and memory size, computers (PC) are classified into following main groups :


    • An analog computer (PC) is one which can perform multiple calculations at once and can cope with infinite fractions of numbers.
    • The term analog does not relate to how the computer (PC) is powered and it is possible to have
      electronic analog computers (PC).
    • The characteristics of an analog computer (PC) mean it can be better than a digital computer (PC) at particular tasks.


    1. Super computer
      • Super computer (PC) is the most powerful and fastest, and also very expensive.
      • It was developed in 1980s.It is used to process large amount of information (data) and to solve the complicated scientific problems.
      • It can perform more than one trillion calculations in per second.
      • It has large number of processors at a time connected parallel.
      • So parallel processing is done in this computer (PC).
      • In a single supercomputer thousands of users are often connected at an equivalent time and therefore the supercomputer handles the work of every user separately.
      • Super computer (PC) are mainly used for:
        • Weather forecasting
        • Nuclear energy research
        • Aircraft design
        • Automotive design
        • Online banking
        • To control industrial units
    2. Minframe computer:
      • Mainframe computers (PC’s) are large-scale computers but supercomputers are larger than mainframe.
      • The mainframe computer (PC) specially requires a very large clean room with air conditioner.
      • It can support a large number of varied equipments.
      • It also has multiple processors. Large mainframe system can handle the I/O(input and output) requirements of several thousands of users. For instance IBM (International Business Machines), s/390 mainframe can support 50000 users simultaneously.
    3. Mini Computer
      • These are smaller in size, have lower (small) processing speed and also have lower cost than mainframe.
      • These computers (PCs) are known as minicomputers because of their small size as compared to other computers (PCs)
        at that time.
      • The capabilities of a minicomputer are between mainframe and personal computer (PC).
      • These computers are also known as midrange computers (PCs).
      • The minicomputers are used in business, education (study) and many other government departments.
    4. Micro computer
      • The micro computers (PCs) are also known as personal computers or simply PCs, Microprocessor is a used in this type of computer (PC).
      • These are very small in size and cost. The IBM’s first microcomputers were designed in 1981 and were named as IBM (International Business Machines) – PC.
      • After this many computer (PC) hardware companies copied the design of IBM (International Business Machines) -PC.
      • The term “PC-compatible” refers any personal computer (PC) based on the original IBM (International Business Machines) personal computer (PC) design.
      • The most popular types of personal computers are the PC and therefore the Apple.


    • Hybrid computer (PC) is a digital computer (PC) that accepts analog signals (wave), converts them to digital and processes them in digital form.
    • This integration is obtained by two part digital to analog and analog to digital converter.
    • A hybrid computer (PC) may use or produce analog data or digital information (data).
    • It accepts a continuously varying input, which is then converted into a group of discrete values for digital processing.
    • A hybrid computer (PC) system setup offers a cost effective method of performing complex simulations.
    • A hybrid computer (PC) capable of real time solution has been less expensive than any equivalent digital computer (PC).
    • Hybrid computers (PCs) are necessary for successful system development.
    • An example of a hybrid computer (PC) is the computer (PC) used in hospitals to measure the heartbeat of the patient.
  • Computer Input Devices
    • An input device feeds information (data) to the computer (PC) system for processing.
    • We are going to discuss the most commonly used in input devices in this article.


    • The computer (PC) keyboard is to enter text information (data) into the computer (PC).
    • The main use of the keyboard is to type commands directing the computer (PC) to perform certain actions.


    • A device that controls the change of the cursor or pointer on a monitor.
    • A mouse may be a small object you’ll roll along a tough , flat surface.
    • The invention of the mouse is formed by Douglas Engelbart of Stanford research facility in 1963.


    • Joysticks and similar game controllers can also be connected to a computer (PC) as pointing devices.


    • A scanner may be a device that images a printed page or graphics by digitizing it, producing a picture made of tiny pixels of various brightness and color values which are represented numerically and sent to the computer (PC).
    • Scanners not only scan graphics, but they will also scan pages of text.

    MIDI Devices

    • MIDI (Musical Instrument Digital Interface) may be a system design to transmit information between electronic musical instruments.


    • The trackball is kind of like an upside-down mouse, with the ball located on top.
    • You use your fingers to roll the trackball, and internal rollers (similar to what’s inside a mouse) sense the motion which is transmitted to the computer (PC).
    • Trackballs have the characteristics over mice in that the body of the trackball remains stationary on your desk.

    Graphics Tablet

    • A graphics tablet consists of an electronic writing area and a better“pen” that works with it.
    • A graphics tablet allows creating graphical pictures with motions and actions.
  • Computer Output Devices


    1. Monitors, commonly called as Visual Display Unit (VDU), are the main output device of a computer (PC).
    2. It forms images (picture) from tiny dots, known as pixels that make an arrangement in a form of a rectangular form.
    3. The sharpness of the image (picture) depends upon the number of pixels.


    The printer is an output device, which is to print information (data) on paper.

    There are two types of printers:

    1. Impact Printers
    2. Non-Impact Printers


    1. A plotter is a printer that interprets commands from a computer (PC) to make line drawings on paper with one or more automated pens.
    2. Unlike a regular printer, the plotter can draw continuous point-to-point (P2P) lines directly from vector graphics files or commands.


    • A projector or image (picture) projector is an optical device(or other electromagnetic radiation), which projects an image (or moving images) onto a surface, commonly a projection screen.


    1. Speakers are one of the most common output devices with computer (PC) systems.
    2. Some speakers are designed for work specifically with computers (PCs), while others are often attached to any type of sound system.
  • Memory
    Memory is the storage space in the computer (PC) where data (information) get the process and instructions required for processing get store. The memory is split into a large (an outsized) number of small parts referred to as. Each location or cell features a unique address which varies from zero to memory size minus one.

    Memory is of three types

    • Cache Memory
    • Primary Memory
    • Secondary Memory

    Cache Memory

    Cache memory is (may be) a very high-speed semiconductor memory which which may speed up CPU. It acts as a buffer between the CPU (Central Processing Unit) and main memory.

    Primary Memory (Main Memory)

    1. Primary memory holds only those data (information) and instructions on which computer is currently working.
    2. It has limited capacity and data (information) is lost when power is switched off.
    3. it is generally made from the semiconductor unit.
    4. The data (information) and instruction require being processed reside in main memory.

    There are two sub-categories ROM (Read-Only Memory) and RAM (Random Access Memory) in Primary memory.

    RAM :

    The RAM (random access memory) is the place in a computer (PC) where the operating system, application programs, and data (information) in current use are kept.

    RAM is much faster to read from and write to than the other kinds of storage in a computer (PC), the hard disk, floppy disk, and CD-ROM.

    It has two parts:

    A. SRAM: Static Random Access Memory

    B. DRAM: Dynamic Random Access Memory.


    As the name suggests ROM, stores information (data) that can only be read. Modifying it is impossible or very difficult.

    ROM is also a type of non-volatile storage, which means that the information (data) in it stays even if the computer (PC) loses power.

    This is another type of ROM (Read-Only Memory) that is impossible or difficult to change.

    • PROM – Programmable Read Only Memory.
    • EPROM – Erasable Programmable Read Only Memory.
    • EEPROM – Electrically Erasable Programmable Read Only Memory.

    Secondary memory

    Secondary memory is where programs and data (information) are kept on a long-term beginning. Common secondary storage devices are the hard drive disk  and optical disks drive.

    • The hard drive disk has enormous storage capacity compared to main memory.
    • The hard disk is usually contained inside the case of a computer (PC).
    • The hard disk is used for long-term storage of programs and data (information).
    • Data (information) and programs on the hard disk are organized into files.
    • file is a collection of data (information) on the disk that has a name.