ICT Notes NAIROBI T. T.I.
CHAPTER ONE
INTRODUCTION TO COMPUTER STUDIES
What is a computer?
− A computer is an electronic device that works under the control of stored
Programmes (instructions), accepts raw data and processes it into information.
− Information production is a cycle of input, processing and output as shown in the
diagram below.
Input is a way entering/ keying Input Output
data in the computer. Output is a way of receiving
information from the computer. It
can be either softcopy output or
hardcopy output
Process
Processing is the manipulation of
data to achieve certain objectives.
Computer terminologies Itcomparisons
may include calculations,
to produce desired
results.
1. Program-is a step by a step instruction which helps the computer to perform a given
task. It can also be referred to as software.
2. Data - These are raw or basic facts which are meaningless unless undergone
processing. It may include numbers, letters and symbols.
3. Information- is processed data which is meaningful. It also refers to summarized
data.
Parts of a computer
A computer is made up of a collection of different components that are inter-connected
together in order to function as a single entity.
Compiled By: Emmanuel. Page 1 of 101
,ICT Notes NAIROBI T. T.I.
i) System unit- This is the part that houses the brain of the computer called central
processing unit (CPU). It also houses other devices like: - Drives, Motherboard,
Power supply unit, Hard disk etc. Drives are used to store (write), record and read
data. There are two common types of system units namely: Tower system unit
and Desktop system unit.
Desktop system unit
Tower System unit
ii) Monitor/ Visual Display Unit (VDU)/ Screen- It is a television like device used
for displaying output. It is called the monitor because it enables the user to
monitor or see what is going on in the computer.
iii) Mouse- It is a device that enables the user to issue instruction in the computer by
controlling a special mouse pointer displayed on the screen. It is a pointing device
mainly used in Graphical User Interfaces (GUI).
iv) Keyboard- It is a device that enables the user to enter data and instruction in the
computer by pressing its keys.
NB: Devices connected together to the system unit using cables are called peripheral
devices. Examples of peripheral devices include: Mouse, Keyboard, Monitor, Scanner,
Speakers e.t.c.
Diagram of computer system
Compiled By: Emmanuel. Page 2 of 101
,ICT Notes NAIROBI T. T.I.
CLASSIFICATION OF COMPUTERS
Computers are classified according to:
1. Physical size and processing power
2. Purpose
3. Functionality
1. Classification according to physical size and processing power
Computers in this category can be classified into 4 main groups namely:
a) Super computers
b) Main frame computers
c) Mini computers
d) Micro computers
a) Super computers
− They are the fastest, largest, most expensive and power computers.
− They are mainly used in scientific research, simulation weapon analysis etc.
Compiled By: Emmanuel. Page 3 of 101
, ICT Notes NAIROBI T. T.I.
− Due to their extreme weight they are kept in a special room.
− Due to their high processing power they generate a lot of heat and therefore they
require special cooling system.
− They are mostly found in developed countries such as USA where they are used for
advanced scientific research such as nuclear physics.
b) Main frame computers
− They are less powerful and less expensive than super computers.
− Although super computers may be described as giant computers, the main frames are
said to be big in size.
− They are used for processing data and performing complex mathematical
calculations.
− They have a large storage capacity and can support a variety of peripherals.
− They are mostly found in government agencies, big organizations and companies
such as banks, hospitals, airports etc, which may have large information processing
needs.
c) Mini computers
− They are physically smaller and cheaper than main frame computers and they are
referred to as small – scale main frame computers.
− They support fewer peripheral devices than mainframes.
− They are less powerful and have less speed than main frame.
− They are used mainly in scientific laboratories, research institutions, engineering
plants and other places where processing automation is required.
− They are well adapted for functions such as accounting, word processing, database
management and specific industry application.
d) Micro computers
− They are the smallest, cheapest and less powerful than any other type of computer.
Compiled By: Emmanuel. Page 4 of 101
CHAPTER ONE
INTRODUCTION TO COMPUTER STUDIES
What is a computer?
− A computer is an electronic device that works under the control of stored
Programmes (instructions), accepts raw data and processes it into information.
− Information production is a cycle of input, processing and output as shown in the
diagram below.
Input is a way entering/ keying Input Output
data in the computer. Output is a way of receiving
information from the computer. It
can be either softcopy output or
hardcopy output
Process
Processing is the manipulation of
data to achieve certain objectives.
Computer terminologies Itcomparisons
may include calculations,
to produce desired
results.
1. Program-is a step by a step instruction which helps the computer to perform a given
task. It can also be referred to as software.
2. Data - These are raw or basic facts which are meaningless unless undergone
processing. It may include numbers, letters and symbols.
3. Information- is processed data which is meaningful. It also refers to summarized
data.
Parts of a computer
A computer is made up of a collection of different components that are inter-connected
together in order to function as a single entity.
Compiled By: Emmanuel. Page 1 of 101
,ICT Notes NAIROBI T. T.I.
i) System unit- This is the part that houses the brain of the computer called central
processing unit (CPU). It also houses other devices like: - Drives, Motherboard,
Power supply unit, Hard disk etc. Drives are used to store (write), record and read
data. There are two common types of system units namely: Tower system unit
and Desktop system unit.
Desktop system unit
Tower System unit
ii) Monitor/ Visual Display Unit (VDU)/ Screen- It is a television like device used
for displaying output. It is called the monitor because it enables the user to
monitor or see what is going on in the computer.
iii) Mouse- It is a device that enables the user to issue instruction in the computer by
controlling a special mouse pointer displayed on the screen. It is a pointing device
mainly used in Graphical User Interfaces (GUI).
iv) Keyboard- It is a device that enables the user to enter data and instruction in the
computer by pressing its keys.
NB: Devices connected together to the system unit using cables are called peripheral
devices. Examples of peripheral devices include: Mouse, Keyboard, Monitor, Scanner,
Speakers e.t.c.
Diagram of computer system
Compiled By: Emmanuel. Page 2 of 101
,ICT Notes NAIROBI T. T.I.
CLASSIFICATION OF COMPUTERS
Computers are classified according to:
1. Physical size and processing power
2. Purpose
3. Functionality
1. Classification according to physical size and processing power
Computers in this category can be classified into 4 main groups namely:
a) Super computers
b) Main frame computers
c) Mini computers
d) Micro computers
a) Super computers
− They are the fastest, largest, most expensive and power computers.
− They are mainly used in scientific research, simulation weapon analysis etc.
Compiled By: Emmanuel. Page 3 of 101
, ICT Notes NAIROBI T. T.I.
− Due to their extreme weight they are kept in a special room.
− Due to their high processing power they generate a lot of heat and therefore they
require special cooling system.
− They are mostly found in developed countries such as USA where they are used for
advanced scientific research such as nuclear physics.
b) Main frame computers
− They are less powerful and less expensive than super computers.
− Although super computers may be described as giant computers, the main frames are
said to be big in size.
− They are used for processing data and performing complex mathematical
calculations.
− They have a large storage capacity and can support a variety of peripherals.
− They are mostly found in government agencies, big organizations and companies
such as banks, hospitals, airports etc, which may have large information processing
needs.
c) Mini computers
− They are physically smaller and cheaper than main frame computers and they are
referred to as small – scale main frame computers.
− They support fewer peripheral devices than mainframes.
− They are less powerful and have less speed than main frame.
− They are used mainly in scientific laboratories, research institutions, engineering
plants and other places where processing automation is required.
− They are well adapted for functions such as accounting, word processing, database
management and specific industry application.
d) Micro computers
− They are the smallest, cheapest and less powerful than any other type of computer.
Compiled By: Emmanuel. Page 4 of 101
