Computer Science

Computer Knowledge For All Competitive Exams PDF

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Computer Knowledge For All Competitive Exams

This blog contains computer knowledge for all competitive exams and recruitment test where computer is mandatory.For your ease,handouts in PDF form can be downloaded here.

Parts Of A Computer:
The computer is composed of two parts:
1) Hardware
2) Software
1) Hardware:
All physical components of computer, to which we can touch,can be
measured, also have weight and occupy some space, are collectively called
computer hardware viz;
i) Keyboard
ii) Mouse
iii) Joy stick
iv) Scanners
v) Monitor
vi) Printer
vii) Central Processing unit etc.
2) Software:
Software is defined as a set of instructions or codes written in a
defined manner. In other words software are prewritten programs,
which control the operations of computer.
All the programs and data stored on a floppy disk, a Hard disk, CD-ROM are collectively called software.
Examples are;
i) DOS
ii) Window
iii) UNIX
v) Linus
vi) Java
vii) MS Office
Devices OR Components Of A Computer:
The computer is a well designed combination of many parts, each of which performs
specific task independently. The major devices of a computer are as
1) Input Devices
The input devices are the devices which send information to
the Central Processing Unit. The main input devices are:
i) KEYBOARD: It is used to enter text. It contains alphabetic, numeric
and other keys for entering data.
ii) MOUSE:It is a pointing device. It controls the pointer on the screen.
iii) MICROPHONE: It is used to enter voice into the computer.
iv) SCANNER: It can read printed text and graphics and then translates the result into digital form.
v) DIGITAL CAMERA:It is used to take photos.
vi) PC CAMERA: We use it to create movie and to take photos on the
A hardware component is used to display piece of information to the user’s
output device.
i) MONITER: It is used to display text, graphics and video output.
ii) PRINTER: It can be used to display printed output on paper.
iii) SPEAKER:It is used to utter sound.
The hardware components are used to store instructions,data and
information permanently are called storage devices. For example
floppy disk drive, zip drive, hard disk drive, CD-ROM drives etc.
These Devices are used to communicate and also exchange data, instructions and
information with other computers. For example Modem.
ALU is a part of CPU. Actual execution of instructions takes place in
this part. Arithmetic and logical operations are always performed in ALU.
It consists of two units:

  1. Arithmetic Unit
    It performs all basic arithmetic functions such as addition of numbers, subtraction,
  2. Logical Unit
    It performs logical operations like comparing two data items to find out amongst all
    which data item is greater , equal to, or less than the other.
    It acts like a supervisor of the computer. It does not execute program
    instruction by itself. It controls and coordinates all activities of
    computer system.
    • Memory Unit (MU)
    It is responsible for the storage of data and information. The memory unit is comprised of
    two types of memory are RAM and ROM.
    Some Important Definitions And Short Notes:
    RAM stands for random access memory. It is that part of CPU where
    temporary information is stored.
    A group comprised of 8 bits is called a byte.
    Pictorial objects which appear on the desktop or user’s screen are called Icons.
    It is an input device, usually called a “Pointing device”. This device is used for pointing anything on monitor through a blinking cursor.
    Any set of instructions or codes written in a defined manner or
    pre-written programs which control the operations of computer.
    Control Unit:
    The unit of CPU which is responsible for all automatic operations carried out by the digital computers is called CU. The CU directs and
    coordinates all activities of a computer.
    LAN stands for local area network. It is privately owned
    communication network that serves users within a confirmed
    geographical area. The range is usually within a mile-perhaps one
    office, one building or a group of buildings.
    It stands for wide area network. It is a communication network that
    covers a wide geographical area. The range is usually a state or a
    country. Examples are Telenet, Uninet etc.
    Modem is abbreviation of Modulate-de-Modulate. Modulation is a
    process that converts digital signals into Analog form and
    Demodulation is a process of converting Analog signals into digital
    form. The device which performs modulation and demodulation is
    called a MODEM. In simple words it is a device that converts the
    digital signals into Analog and then reverse from Analog to digital form.
    The unit of CPU that performs arithmetic and logical operations is called
    Registers are high-speed staging memory locations that temporarily store data
    during processing and provide working areas for computation.
    Registers are contained in control unit and arithmetic Logic Unit.
    Following are the major types of registers:
    i) Address Register
    ii) Instructions Register
    iii) Storage Register
    iv) Accumulator Register
    Soft Copy:
    It displays the data on screen of monitor. It can be carried in a floppy
    disk. Any change can be made in a soft copy.
    Hard Copy:
    The data is printed on paper card etc. with the help of printer. It
    cannot be carried in a floppy disk. No change can be made in hard

Computer Knowledge For All Competitive Exams

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