Computer System Overview
Simple Guide for Students
Subject: Computer Science / Nursing Informatics / General Education
Best for: Nursing, IT, and Allied Health Students preparing for class
tests or practical
, Computer System
What is a computer system?
A contemporary computer system consists of a central processing unit (CPU),
primary storage, secondary storage, input devices, output devices, and
communications devices.
Basic Function of the units of computer system
1. System Unit: A case that contains the electronic "brain" of the computer and the
main computational components of the computer that is used to process data.
2. Storage Devices: Stores and hold data, instructions & information for future
use.
3. Input devices: Computer hardware that allows a user to enter data and
instructions.
4. Output devices: Computer hardware that allows a user to receive information.
5. Communications devices: Hardware components that enables a computer to
send & receive data, instructions & information to or from one or more computers.
Block diagram of a digital computer:
,Input Unit
This unit contains devices with the help of which we enter data into the computer.
This unit creates a link between the user and the computer. The input devices
translate the information into a form understandable by the computer.
❖ Keyboard
❖ Mouse
❖ Joy Stick
❖ Light pen
❖ Track Ball
❖ Scanner
❖ Graphic Tablet
❖ Microphone
❖ Magnetic Ink Card Reader (MICR)
❖ Optical Character Reader (OCR)
❖ Bar Code Reader
❖ Optical Mark Reader (OMR)
CPU (Central Processing Unit)
CPU is considered as the brain of the computer. CPU performs all types of data
processing operations. It stores data, intermediate results, and instructions
(program). It controls the operation of all parts of the computer.
CPU itself has the following three components -
o ALU (Arithmetic Logic Unit)
o Memory Unit
o Control Unit
Output Unit
The output unit consists of devices with the help of which we get the information
from the computer. This unit is a link between the computer and the users. Output
devices translate the computer's output into a form understandable by the users.
, ❖ Monitor (LED, LCD and CRT etc.)
❖ Printer
❖ Speaker
❖ Plotter
❖ Projector
❖ LCD projection panel
❖ Computer output microfilm (COM)
Memory or Storage Unit
This unit can store instructions, data, and intermediate results. This unit supplies
information to other units of the computer when needed. It is also known as
internal storage unit or the main memory or the primary storage or Random Access
Memory (RAM).
Its size affects speed, power, and capability. Primary memory and secondary
memory are two types of memories in the computer. Functions of the memory unit
are-
• It stores all the data and the instructions required for processing.
• It stores intermediate results of processing.
• It stores the final results of processing before these results are released to an
output device.
• All inputs and outputs are transmitted through the main memory.
Control Unit
This unit controls the operations of all parts of the computer but does not carry out
any actual data processing operations.
Functions of this unit are -
It is responsible for controlling the transfer of data and instructions among other
units of a computer.
Simple Guide for Students
Subject: Computer Science / Nursing Informatics / General Education
Best for: Nursing, IT, and Allied Health Students preparing for class
tests or practical
, Computer System
What is a computer system?
A contemporary computer system consists of a central processing unit (CPU),
primary storage, secondary storage, input devices, output devices, and
communications devices.
Basic Function of the units of computer system
1. System Unit: A case that contains the electronic "brain" of the computer and the
main computational components of the computer that is used to process data.
2. Storage Devices: Stores and hold data, instructions & information for future
use.
3. Input devices: Computer hardware that allows a user to enter data and
instructions.
4. Output devices: Computer hardware that allows a user to receive information.
5. Communications devices: Hardware components that enables a computer to
send & receive data, instructions & information to or from one or more computers.
Block diagram of a digital computer:
,Input Unit
This unit contains devices with the help of which we enter data into the computer.
This unit creates a link between the user and the computer. The input devices
translate the information into a form understandable by the computer.
❖ Keyboard
❖ Mouse
❖ Joy Stick
❖ Light pen
❖ Track Ball
❖ Scanner
❖ Graphic Tablet
❖ Microphone
❖ Magnetic Ink Card Reader (MICR)
❖ Optical Character Reader (OCR)
❖ Bar Code Reader
❖ Optical Mark Reader (OMR)
CPU (Central Processing Unit)
CPU is considered as the brain of the computer. CPU performs all types of data
processing operations. It stores data, intermediate results, and instructions
(program). It controls the operation of all parts of the computer.
CPU itself has the following three components -
o ALU (Arithmetic Logic Unit)
o Memory Unit
o Control Unit
Output Unit
The output unit consists of devices with the help of which we get the information
from the computer. This unit is a link between the computer and the users. Output
devices translate the computer's output into a form understandable by the users.
, ❖ Monitor (LED, LCD and CRT etc.)
❖ Printer
❖ Speaker
❖ Plotter
❖ Projector
❖ LCD projection panel
❖ Computer output microfilm (COM)
Memory or Storage Unit
This unit can store instructions, data, and intermediate results. This unit supplies
information to other units of the computer when needed. It is also known as
internal storage unit or the main memory or the primary storage or Random Access
Memory (RAM).
Its size affects speed, power, and capability. Primary memory and secondary
memory are two types of memories in the computer. Functions of the memory unit
are-
• It stores all the data and the instructions required for processing.
• It stores intermediate results of processing.
• It stores the final results of processing before these results are released to an
output device.
• All inputs and outputs are transmitted through the main memory.
Control Unit
This unit controls the operations of all parts of the computer but does not carry out
any actual data processing operations.
Functions of this unit are -
It is responsible for controlling the transfer of data and instructions among other
units of a computer.
