Basic components of computer system

BASIC COMPONENTS OF A
COMPUTER SYSTEM

Basic components of a computer are:

1. Input Unit
 Input is any data or instructions entered into the
memory of a computer
Any hardware component allows user to enter data and
instructions in to a computer.

Keyboard
 Used to enter
information into the
computer and for giving
commands.
 A standard computer
keyboard is called a
QWERTY keyboard

Ball Mouse
 An input device operated
by rolling its ball across a
flat surface. The mouse is
used to control the on-
screen pointer by pointing
and clicking, double-
clicking, or dragging objects
on the screen.

Optical Mouse
 It is an advanced computer pointing
device.
 It uses Light-Emitting Diode(LED) in
place of the traditional mouse ball.
 Movement is detected by sensing changes
in reflected light.

2. Output Unit
 The job of output unit is just the reverse of that of an
Input Unit.
It supplies information and results of computation to
the outside world.
Monitor and Printer are the most common
Output Devices which are used.

Monitor
A display screen is used
to provide “output” to
the user. It is where you
can view the
information you are
working on.

Printer
An output device that
produces a hard of the
information.
Information to the user
is in printed form.

3. Memory / Storage
Devices
 All computer need to store data.
Data is stored temporally while program is running
– Main Memory.
To store data for long-term, to preserve programs and data
while not in use – Backing Storage.
Primary Memory and Secondary Memory

Primary Memory
 Temporary area for holding data.
To store the program currently being executed
To hold data produced while the programe is running.
Primary Memory are of two types
1. RAM &
2. ROM

1.RAM(Random Access Memory)
 Major portion of the Primary Memory
 Memory that is used by the program in execution
 If the computer gets turned off, RAM will lose all
the data.
Static RAM & Dynamic RAM

Static RAM
The memory retains as long as power remains
applied.
Uses Flip Flop circuitory.
Is more faster.

Dynamic RAM
 Need continues Refreshing in order to
maintain the data.
 It uses transistors and capacitors in circuits
 Slow and consumes more power

2.ROM (Read Only Memory)
 Memory which we can only read but cannot
write on.
 Non-volatile.
 Used to store some firmware programs.
PROM – Programmable Read Only Memory
EPROM – Erasable and Programmable read Only Memory.
EEPROM – Electrically Erasable and Programmable read Only Memory.

Secondary Memory
Permanent memory of the system.
More storage capacity.
It is the Backing Store.
Magnetic Disk & Optical Disk

Magnetic Disc
Stored data in the form of
Magnetic directions.
Hard Disk & Floppy Disk

Hard Disk
Access to data is far faster than
access to data in floppy disks.
Read/Write Head is positioned close
to the disk.
Disk is attached to a spindle.
Spindle is rotated by a motor.
Speed of disk depends on the speed
of motor.

Floppy Disk
• Consists of a plastic disk coated with iron oxide.
• Disk access mechanism is arranged as a hardware unit
called disk drive.
• Drive contains motor, Read/Write Head etc.
• Head comes in contact with the disk through the data
access area.
• Disk is rotated to pass the sectors through the head.

Optical disk
It is an electronic storage medium.
Read operation is done using low powered
laser beam.
A laser read the dots and then the data is
converted to an electrical signal .
The output form of this devise is in audio
and visual format
CD-ROM – Compact Disk-Read Only Memory.
CD – R – Compact Disk – Recordable.
CD-RW – Compact Disk – Rewritable
DVD – ROM – Digital Versatile Disk – Read Only Memory
DVD – RAM - Digital Versatile Disk – Random Access Memory

4.Processor Or CPU
 The CU and ALU are jointly known as
CPU.
 Brain of the computer.
 Perform data processing operations.
 Control the working of the entire system.
Arithmetic and Logic Unit (ALU) & Control Unit(CU)

Arithmetic and Logic Unit ( ALU )
Place where the actual execution of the instructions take place
during the processing operations.
All calculations are performed here.
It consists of circuits that perform arithmetic as well as logical
operations.

Control Unit
It act as a central nervous system for the
other components of the computer.
It manages and coordinates the entire
computer system.
It get information from the main memory
It issues signal to control every other units
of the system.

Basic components of computer system

Basic components of computer system

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