Computer overview

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COMPUTER: - Computer is an electronic device which takes some input, perform operation and after processing give output.

CENTRAL PROCESSING UNIT (CPU): - The CPU is the control centre for a computer. It guides, directs and governs its performance. It is the brain of the computer. The CPU has two components which are responsible for different functions. These are Control Unit (CU) and Arithmetic Logic Unit (ALU).

ARITHMETIC LOGIC UNIT (ALU): - It performs all the arithmetic operations (+,-,*, /) and logical operation (<,>, =, <=,>=, <>).

CONTROL UNIT (CU): - The CU controls and guides the interpretation, flow and manipulation of all data and information.

INPUT UNIT: - The input unit is formed by the input devices attached to the computer. An input unit takes the input and converts it into binary form so that it can be understood by the computer. Example: - Keyboard, mouse, mike, joystick etc.

OUTPUT UNIT: - The output unit is formed by the output devices attached to the computer.

Example: - monitor, speaker, printer.

MEMORY: - The memory of computer is often called main memory or primary memory. It is generally the third computer of CPU.

HARDWARE: - Hardware are those mechanical components which can be seen, touch and repairable.

Example: - C.P.U, keyboard, mouse etc.

SOFTWARE: - Software are those components which cannot be feel and touch, we can only seen them.

OPERATING SYSTEM: - An operating system is a program which acts as an interface between a user and the hardware (i.e., all computer resources).

LANGUAGE PROCESSOR: - Language processors are the devices which converts one type of language into other type of language.

ASSEMBLER: - An assembler is a language translator which converts assembly language into low level language.

INTERPRETER: - An interpreter is a language translator which converts high level language into low level language in line by line method and generates error if any.

COMPILER: - A compiler is a language translator which converts high level language into low level language and also generates error if any. It converts the language in one go method.

APPLICATION SOFTWARE: - Application software is that software which is used for general requirements like, Railway reservation, online reservation etc. This is also used for specific application.

COMPUTER PERIPHERALS: - These are the device that surrounded by the system unit or CPU

Example: - keyboard, mouse, speaker etc.


Abacus – Around 3000 B.C. – The Mesopotamious

Napier’s ‘logs’ and ‘Bones’ – John Napier

Pascal’s Adding machine – Blaise Pascal – 1642

Leihnitz’s Calculator – Gottfried Leibnitz – 1671

Jacquard’s loom – Joseph Jacquard – 1801

Babbage’s difference engine – Charles Babbage – 1822

Babbage’s Analytical engine – Charles Babbage – 1833

Hollerith’s Machine – Herman Hollerith – 1887

Mark I – Prof. Howard Aiken – 1943


The term ‘computer generation’ is often used in relation to the hardware of computers. Each phase of computer development is know as a separate generation of computers. Each phase of development is characterized by type of switching circuits it utilizes


Some key features of first generation computers are :

    • Used vacuum tubes

  • Big and clumsy computers

  • Electricity consumption high

  • Electric failure occurred regularly – computer not very reliable

Large air conditioners were necessary because the computer generated heat

  • Programming in machine language


  • Transistor replaced vacuum tube

  • Generated less heat

  • Computer become smaller

  • Core memory developed

  • Magnetic tapes and disks used

  • Electricity consumption lower

  • First operating system developed

  • Faster


Some key features of first generation computers are :

  • Integrated circuits developed

  • Power consumption lower

  • Computer smaller, faster and more reliable

  • High-level language appeared


Some key features of first generation computers are :

  • Integrated circuit, smaller and faster

  • Micro computer series such as IBM and APPLE


  • Portable computers developed

  • Great development in data communication

  • Different type of secondary memory with high storage

capacity and fast access developed


Some key features of first generation computers are :

  • Parallel-processing – many processors are grouped to function as one large group processor.

  • Superconductors – a superconductor is a conductor which electricity can travel without any resistance resulting in faster transfer of information between the components of a computer

Type of computers

The computers have been classified into thee categories. They are given below:

  1. Digital Computer

  2. Analog Computer

  3. Hybrid Computer

DIGITAL COMPUTER: - A computer that performs calculations and logical operations with quantities represented as digits, usually in the binary number system. Every computer has a set of instructions that define the basic functions it can perform. Sequences of these instructions constitute machine-language programs that can be stored in the computer and used to tailor it to an essentially unlimited number of specialized applications.

ANALOG: - A computer or computational device in which the problem variables are represented as continuous, varying physical quantities. An analog computer implements a model of the system being studied. The physical form of the analog may be functionally similar to that of the system, but more often the analogy is based solely upon the mathematical equivalence of the interdependence of the computer variables and the variables in the physical system.

HYBRIDE: - Hybrid computer utilize the best qualities of both the digital and analog computers. In these computers some calculations take place in analog manner and rest of them take place in digital manner. Hybrid computers are best used in hospital where analog part is responsible for measurement of patient’s heart beat, blood pressure, manner and rest of them.

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