Computer Science Notes
Computer Science Notes
“The word Computer is derived from compute which means to calculate. In simple and
technical term it is an automatic electronic calculating machine that processes or
manipulates a given data according to a program or set of instructions and gives a desired
Parts Of A Computer:
The computer is composed of two parts:
All physical components of computer, which can be touched, measured, have weight and occupy
space, are collectively called computer hardware viz;
iii) Joy stick
vii) Central Processing unit etc.
Software can be defined as a set of instructions or codes written in a defined manner. In other
words softwares are prewritten programs, which control the operations of computer.
All programs and data stored on floppy disk, Hard disk, CD-ROM are collectively called
softwares. Examples are;
vii) MS Office
Devices OR Components Of A Computer:
The computer is a combination of many parts, each of which performs specific task
independently. The major devices of a computer are as under.
1) Input Devices
The input devices are those devices which send data or information to the Central Processing
Unit. The main input devices are:
i) KEYBORD: It is used to enter text. It contains alphabetic, numeric and other keys for entering
ii) MOUSE:It is a pointing device. It controls the pointer on the screen.
iii) MICROPHON: It is used to enter voice into the computer.
iv) SCANNER: It reads printed text and graphics and then translates the result into digital form.
v) DIGITAL CAMERA:It is used to take photos.
vi) PC CAMERA: It is used to create movie and to take photos on the computer.
2) OUT PUT DEVICES:
A hardware component used to display information to the user output device.
i) MONITER: It is used to display text, graphics and video output.
ii) PRINTER: It is used to display printed output on paper.
iii) SPEAKER:It is used to hear sound to hear sound music and voice outputs.
3) STORAGE DEVICE:
The hardware components used to store data, instructions and information permanently are called
storage devices. For example floppy disk drive, zip drive, hard disk drive, CD-ROM drives etc.
4) COMMUNICATION DEVICES:
It is used to communicate and exchange data, instructions and information with other computers.
For example Modem.
UNITS OF CPU:
• ALU(ARTHMETIC AND LOGICAL UNIT)
ALU is a part of CPU. Actual execution of instructions takes place in this part. All arithmetic and
logical operations are performed in ALU. It consists of two units:
1. Arithmetic Unit
It performs basic arithmetic functions such as addition, subtraction, division.
2. Logical Unit
It performs logical operations like comparing two data items to find which data item is greater
than, equal to, or less than the other.
• CONTROL UNIT
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 storage of data and information. The memory unit consists of two types of
memory which 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
A group of 8 bits is called a byte.
Pictorial objects on the desktop or screen are called Icons.
It is an input device, normally called a ―Pointing device‖. This device is used for pointing
anything on monitor through a blinking cursor.
A set of instructions or codes written in a defined manner or prewritten programs which control
the operations of computer.
A 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 that converts 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 back from Analog to
A unit of CPU that performs arithmetic and logical operations is called ALU.
Registers are high-speed staging areas 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
i) Address Register
ii) Instructions Register
iii) Storage Register
iv) Accumulator Register
It displays the data on screen of monitor. It can be carried in a floppy disk. A change can be made
in a soft 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 copy.