The parts of a computer system
Computer
Input
Output
Storage
Data
Information
Hardware
Software
Peripheral
Main memory
Central Processing Unit
Arithmetic and Logic Unit
Control Unit
A computer is a programmable electronic
device that processes data following a set of
instructions.
An example of a fairly simple computer is a
calculator: it can process data and output the
information from the processing.
Data is all the raw facts and figures that a computer
processes by following a set of instructions called
program.
Data by itself has no meaning; it can be in the form
of letters (a, x, t, etc), numbers (1, 4, 7, 534, etc),
pictures, sounds or symbols. It is only when we
attach meaning to data that we get Information.
To process data to produce information, a
computer needs both hardware and software.
Hardware is called the parts of the computer
system you can see and touch. It is all the
devices that make up the computer system.
These devices are also called peripherals
devices.
Software is a set of instructions that a computer
needs to carry out its tasks.
For example, if you want to use the computer to
type a letter, or draw a picture you need different
types of software to accomplish these tasks.
Eg. Word, Excel, Paint, Spider solitaire, FreeCell,
Minesweeper, etc
Process
Output
Output
Output
Input
Input
Input
Processing data to get information involves
three stages. These are input, processing and
output.
Input devices such as
are used to get data and instructions
into the computer for processing.
The processing takes place in that part of the
computer called the Central Processing Unit
(CPU). The CPU is the ‘brain’ of the computer.
It takes the raw data and turns it into
information.
The CPU is made up of two smaller units. These
are the Control Unit (CU) and the Arithmetic and
Logic Unit (ALU).
The Control Unit (CU) is the main part of the CPU.
Input is first sent to the CU, from where it is then
sent to the allocated part of the computer to be
processed. The CU decided where to send data to
be processed. After processing, the information
is returned to the control unit.
The Arithmetic and Logic Unit (ALU) performs all
the arithmetic and logic functions in a computer.
This involves addition, subtraction, multiplication
or division or the comparison of data. Some of the
logic functions are comparisons such as:
Equal to =
Less than <
Less than or equal to <=
Greater than or equal to >=
Not equal to <>
Greater than >
The
main
accessible
memory,
to
the
which
CPU,
holds
is
directly
data
and
instructions that the computer is processing
at the time.
Output devices such as printers, speakers and
visual
display
units
translate
information
processed by the computer into a form which the
user can understand.
After processing, the data and information can be
either stored in a secondary storage device, such
as a disk, or sent to an output device, or both.
Storage refers to media and devices used by a
computer to keep data and instructions available
for immediate or later use.
Storage can be grouped into two categories:
primary storage and secondary storages.
All input, output and external storage devices are
collectively called peripheral devices.
1. Speed – computers are very fast; they can
perform tens of millions of operations per
second. This capacity can be useful for
operations
such
as
predicting
weather,
performing scientific research and producing
thousands of bills for utility companies.
2. Accuracy – computers are very accurate.
Error only occurs if there is an error in the
hardware, software or data.
3. Storing large amount of information in a
small space – there are many storage media
that can be used to store large volumes of
data and information. Eg. CD, DVD, Flash
drive, Hard disk drive

4. Working continuously – computers can work
continuously for long periods without much
maintenance.
Many
permanently switched on!
computers
are
1.
Find two other definition of a Computer.
2.
List 2 other Input, Output and Storage
devices not mentioned in the notes.
A
B
C
E
D
H
G
F
A
2. For each part
B
C
say whether it is
an input,
an output or a
E
D
process device:
H
G
F
3. Explain the following terms and provide an
example for each:
a. Input device
_____________________
b. Output device _________________________
4. State whether the following are hardware
or software:
a. Scanner ____________________________
b. Microsoft Word 2003___________________
c. Speakers
____________________________
d. Microsoft Windows XP__________________
e. Compact Disk (CD)____________________
f. Internet Explorer______________________
g. Diskette
_________________________