COMPUTER HARDWARE

Computer hardware are the physical tangible parts of the computer that you can touch ,see
and feel plus any other devices that is physically connected to a computer (computer
peripherals).

Computer peripherals

These are the external devices connected to the computer system. Computer hardware has
been divided into five namely input, output, processing, storage and communication
devices (network devices).

Input device – These are devices used in entering data in a computer in digital format .Note
that the input could be text, number, letters and formula, images, sound etc.

Examples of input devices

a) Keyboard
b) Mouse
c) Scanner
d) Joystick
e) Light pen
f) Microphone
g) Camera
h) Touch screen

a) Keyboard –It is a plastic board with number of buttons on it known as keys. Some keys
are marked with numbers and letters. Entry of data into the computer is done by
pressing these keys.
Keyboard has been divided into five parts (layout) namely;
I. The alphanumeric keys (typing area)
II. The functional keys
III. The numeric keys
IV. The arrow keys / the navigation keys /cursor keys.
V. Special keys.

Typing area – it consists of keys that are labelled a-z and that are used to construct; the
number 1-9 is also part of typing area.

Function keys-These are keys found across the top row of the keyboard. Each key is
composed of letter F and a number ranging from 1 to 12.Each functional key performs a
specific operation based upon the software being used.

Arrow keys –the cursor movement keys are used to move the cursor
around the screen. The cursor is appointing stick on the screen that
shows where the text or character will be inserted.

The numeric pad – This is an extra section to the right of the

keyboard .it combines numeric buttons and other special purpose
keys. To activate the numeric pad you press the num lock key.

Special purpose keys – we can use special purpose keys with other keys to produce
command.e.g
They include;
Shift key, Tab key, Control key, Caps Lock, Num Lock, Backspace key, Enter key, Delete
key, Alt key, etc.
Functions of some selected keys on the keyboard
Backspace Key
- Deletes the characters to the left of the cursor (or insertion point) and moves the
cursor to that position.
Caps Lock Key
- A toggle key that, when activated, causes all alphabetic characters to be uppercase.
 - To facilitate continuous typing in upper case when activated.
Delete Key
- To remove the character, space, text or word to the right of the cursor position.
– Sometimes labeled Del, deletes the character at the current cursor position, or the
selected object, but does not move the cursor.

Space bar
- To create space.
- Moving the cursor to the next line.
- Pausing music in some music programmes e.g. Power DVD,
Shift Key
- Activates second function of different keys.
- Selects files and folders in specific order
Ctrl key
– Short for Control, this key is used in conjunction with other keys to produce
control characters.
Enter Key
– Used to enter commands or to move the cursor to the beginning of the next
line. Sometimes labeled Return instead of Enter.
Esc Key
– Short for Escape, this key is used to send special codes to devices and to exit (or
escape) from programs and tasks.
Alt key
– Short for Alternate, this key is like a second control key.

b) MOUSE
This is appointing device that is used to select, open and move the
items on the desktop.

They are two types of mouse namely;

 Mechanical mouse
 Optical mouse

Mechanical mouse – is the mouse that tracks motion mechanically, using a

ball, a set of rollers and built in sensor. As the mouse is moved across a flat
surface the ball is rolling motion is detected by the rollers and sensors.
Optical mouse – appointing device that tracks its location and
(the pointer location on the screen) by using a beam of light.

c) MICROPHONE
This is an input device used to input sound in computer.

d) LIGHT PEN

Appointing device shaped like a pen that is used to select items with
direct contact with the screen.

e) TOUCH SCREEN

These are special types of VDU (visual display unit) that enable
users to interact with the computer by simply touching the
screen. They are suitable for people who find it hard to use the
mouse.

f) JOY STICK
This is an input device used for video games and for some
graphics application. A joy stick is similar to a mouse except
that with a mouse the cursor pointer stops moving as you stop
touching the mouse, but with the joystick the cursor pointer
continues moving in the direction of the joystick until you
return the joy stick to its upright position.
 g) DIGITAL CAMERA
This allows the user to take pictures and stores photographic
image in digital format that can be used by the computer.

h) SCANNER
This is an input device used to translate images, text or
drawing directly into digital format that the computer
can use.

TYPES OF SCANNER
 Barcode reader
 Magnetic ink character reader
 Intelligent character reader
 Optic character reader

Barcode reader –
This is an electronic device used for reading printed codes. It is used
in the supermarket to read the coded price tag on the items.

N/B Barcodes are vertical lines printed on the items.

Magnetic character reader-is an input device that reads the strange numbers of printed at
the bottom of the cheque.

Intelligent character reader – is special or advanced technology system that is used to

translate a wide range of written document into the computer.

Optical character reader- is a scanning device used to translate pre-printed fonts into the
computer.
Biometric Input
Biometrics is the t e c h n o l o g y o f authenticating a p e r s o n ’ s identity b y
verifying a personal characteristic. Biometric devices grant users access to programs,
systems, or rooms by analyzing some biometric identifier.
A biometric identifier is a physiological (related to physical or chemical activities
in the body) or behavioral characteristic.

Examples include fingerprints, hand geometry, facial features, voice, signatures, and
eye patterns.
Biometric devices
A biometric device is an input device that translates a personal characteristic into a
digital code that is compared with a digital code stored in the computer.
If the digital code in the computer does not match the personal characteristic's
code, the computer denies access to the individual.
Examples of biometric devices

A fingerprint scanner;
A fingerprint scanner captures curves and
indentations of a fingerprint. Some grocery and
retail stores now use fingerprint readers as a
means of payment, where the customer's
fingerprint is linked to a payment method such
as a checking account or
credit card.

A face recognition system;

This captures a live face image and compares it with a
stored image to determine if the person is a legitimate user.
Some buildings use face recognition systems to secure access
to rooms. Law enforcement, surveillance systems, and airports
use face recognition to protect the public.
Some n o t e b o o k computers u s e this security technique to
s a f e g u a r d a computer. The computer will not start unless
the user is legitimate

These programs are becoming more sophisticated and can recognize people with or
without glasses, makeup, or jewelry, and with new hairstyles
A hand geometry system;
These measure the shape and size of a person's hand. Some large companies use this
system as time and attendance devices or as security devices. Day-care centers use this
system to verify parents who pick up their children.

A voice verification system;

A voice verification system compares a person's live speech with their
stored voice pattern. Some larger organizations use voice verification
systems as time and attendance devices. Many companies also use this
technology for access to sensitive files and networks. Some financial services
use voice verification systems to secure telephone banking transactions.
These systems use speaker-dependent voice recognition software. That is,
users train the computer to recognize their inflection patterns.

A signature verification system;

A signature verification system recognizes the shape of your handwritten
signature, as well as measures the pressure exerted and the motion used to write
the signature.
Signature verification system uses a specialized pen and tablet.

An iris recognition
system; High security areas use iris recognition systems. The camera
in an iris recognition system uses iris recognition
technology to read patterns in the iris of the eye.
These patterns are as unique as a fingerprint. Iris recognition
systems are used by government security organizations, the
military and financial institutions that deal with highly
sensitive data. Some organizations use retinal scanners,
which work similarly but instead scan patterns of blood
vessels in the back of the retina.
CENTRAL PROCESSING UNIT
The central processing unit is hardware within the P ro ce ss in g d e v ic es

computer system which carries out the instruction of the

computer. Programme by performing the basic arithmetic,
logic and output operation of the system. The CPU can be
described as the brain of the computer or the heart that
monitors all the computer components.

The CPU is made of three main parts namely;

 Control unit (CU)

 Arithmetic and Logic unit (ALU)
 Main memory

COMPUTER FUNCTIONAL ORGANIZATION CHART

FUNCTIONS OF THE COMPONENTS OF CPU

CONTROL UNIT
 Directs sequence of operation
 Interprets instructions and gives commands
 Communicates with input and output device for transfer of data into / from
storage
 Controls all the activities in the CPU.

Arithmetic and logic unit

Performs arithmetic functions
Does logical comparison

Main memory
Holds data during processing
Holds immediate results (output)
All inputs and output are transmitted through the main memory.

Main memory is a temporal storage that process data and programme instruction
waiting to be processed by the computer.

Main memory has been further divided into two namely;

 ROM (read only memory)

 RAM (random access memory)

RAM (random access memory)

It is the main memory of the computer. It is also called
volatile; it is volatile because it loses its content when
power is switched off.

RAM has been sub divided into two namely;

 Static RAM
 Dynamic RAM
 ROM (read only memory)
It is a memory chip which stores data and instruction
permanently. It is non-volatile because it does not lose
its content when power is switched off and can’t be
modified (changed).

ROM has been classified into three namely;

 Programmable read only memory (PROM)

 Erasable programmable read only memory (EPROM)
 Electrical erasable programmable read only memory (EEPROM)

1) PROM; it allows its content to be changed only once after the content is written
on.
2) EPROM; its contents can be erased by the use of ultra violet rays and then re-
programme it
3) EEPROM; it can be erased and re- programmed using electricity current.

Differences between RAM and ROM

RAM ROM
RAM is volatile ROM is non-volatile
RAM data content is temporal Data content is permanent
RAM is read and write ROM is read only memory
RAM can be modified ROM can’t be modified

Other forms of memory

Flash memory; is a memory used in notebook and tablet computer cellular phone and
digital camera. Flash memory is non-volatile.

Video memory /video ram chip; are used to store displaying images on the
computer.
Cache memory; is a memory that resides between CPU and the main memory. Cache
memory is special high speed memory area that the CPU can access quickly. Cache
memory stores data that is needed immediately by the running process.

Virtual memory; stores data that are not needed immediately by to running process.

Machine cycle; is series of operation that computer performs to execute a single

programme.

Machine cycle has been divided into four operations namely;

 Fetching
 Decoding
 Execute
 To store /write back
Diagram for machine cycle
Before an instruction can be executed, programme instruction and data must be placed into
memory from input or secondary devices. The CPU performs the following steps for each
instruction;
I. The control unit fetches instructions from the main memory
II. The control unit fetches the code, the instructions and directs that necessary data to
be moved from main memory to arithmetic logic unit.
III. Arithmetic logic stores the results of this operation in the main memory.
IV. The arithmetic logic unit executes the arithmetic or logical instructions.

Storage device/ media

A storage device is hardware component or physical material that keeps or stores data or
instruction for future or immediate use.

Storage device is hardware component that reads and writes to and fro the storage media.

N/B
Reading refers to the process of transferring files from the storage media to the main
memory (RAM) while writing is the process of transferring files from the main memory to
the storage media.

Primary storage is the main memory (hard disk/ RAM) where the operating system resides
while secondary storage can be external devices (media) like CD, floppy that cannot be
directly accessed by the CPU.

Transfer rate – This is time required to transfer data or read from the disk into main
memory (RAM). It is the time required to write data on the disk from main memory OR this
is the speed with which data, instructions, and information transfer to and from a device.
While
Access time –This is the amount of time it takes a device to locate an item on a medium
(media) and make it available to the computer OR this refers to the speed of a storage
device and memory.

Examples of storage media and device

Media Device
Flash disk Flash disk drive
Hard disk Hard disk drive
Compact disk Compact disk drive
Memory card Memory card drive
Floppy disk Floppy disk drive

Storage capacity is the amount of memory that a given storage media can store or hold.
The smallest unit that a computer can store is bit.
Storage capacity units

Bit (0, 1)
Byte (8bits)
Kilobyte (1000bytes)
Megabyte (1000000bytes)
Gigabyte (1000000000bytes)
Terabyte (1000000000000bytes)
Petabyte (1024terabyes)
Exhabyte (1024 petabytes)

Categories of secondary storage media

Storage media has been categorized into 3 classes

 Magnetic secondary storage media

 Optical secondary storage media
 Magneto-optical secondary storage media (solid state storage media)

Magnetic storage media; here devices store data in a magnetic format or they use magnetic
fields to capture data in them.

Examples include;
 Floppy disk
 Hard disk

Floppy disk
A floppy disk is a portable in expensive storage media which
consist of a pin circular flexible plastic disk with a magnetic
coating enclosed in a square shaped plastic shell.

Precautions and care for the diskette (floppy disk)

 It should not be exposed to heat
 It should not be exposed to dust
 Don’t drop the diskette to the ground
 Don’t exposed it to magnetic fields
 Should not be exposed to coldness
 Avoid folding the diskette
 Avoid touching the inner magnetic area
 Never leave the diskette in the drive.
Differences between hard disk and floppy disk
Hard disk Floppy disk
It has high storage capacity of 160GBS It has a low storage capacity of 44MBS.
It is portable It is more portable
It is expensive It is cheap
Data access is very fast Data access is very slow

Optical secondary storage media; Here devices use light beam technology or reflective
materials to capture data and information in them.

Examples include;

CD- ROM (compact disk read only memory)

The content is written by the manufacturer or company and can only be read and used.

CD-R (compact disk recordable)

This allows data to be written on the disk once and read
many times.

CD-RW (compact disk rewritable)

This allows you to read and write many times.

Solid state /magneto-optical media

Here devices use both magnetic field and light beam to capture data and information in
them.

Examples include;
 Flash disk
 Memory card
 Smart card

Output devices
These are hardware components that enable that user to get the end results /product from
the computer.

There are two forms of output namely;

 Soft copy output
 Hard copy output
Soft copy – refers to data is shown on a display screen or is in audio or voice form. This type
of output is not tangible.
Hard copy – refers to printed output, for example printed texts or graphics, printers.
The common output devices include;
Printers
Speakers
Monitors
Web camera
Plotters
Projectors

Categories of computer output devices include;

Text output devices

 Printer
 Plotter

Audio output devices

 Speakers
 Headphones

Graphic output devices

 Projector

Video output devices

 Monitor

Displaying devices
These are output devices that visually convert a text, graphic and video information shown
on the screen.

The common displaying devices include;

 Cathode ray tube
 Liquid crystal display

Cathode ray tube monitor

This is desktop screen that contains a large sealed glass
called cathode ray tube.

Disadvantages of cathode ray tube (CRT)

 They consume a lot of power
 Emit higher electromagnetic radiation which can cause health problem to the user.
 They consume a lot of space
 They are bulky and not portable like LCD monitor.

Advantages of cathode ray tube (CRT)

 They provide a wide angle of view.
 They are cheap compare to LCD monitors in general
 Technical personnel to repair CRT are many unlike the LCD monitors.

Liquid crystal display monitor

It is a light weight display with a shallow depth and flat
screen that typically uses LCD technology.

Advantages of LCD
 Don’t produce much heat
 They take up less space unlike the CRT monitors
 Radiation emitted by LCD monitors is negligible
 They consume less power
 They are portable
 They display clear images.

Disadvantages of LCD
 They provide a narrow angle of view.
 They are usually expensive.
 They need highly trained personnel to repair them

Projector
A projector is an output device that project images onto a large
white screen so as to give a wider view for a large audience.

Printer
A printer is an example of output device that produces
hardcopy output e.g. text book, graphics, e.t.c.on a physical
material e.g. paper (print media).

Printers can be grouped into two categories namely;

 Impact printers
 Non-impact printers

Impact printers
These are printers whose printer heads come in contact with the paper (print media) while
printing they are using striking mechanism.
Examples of impact printers include;
 Dot matrix
 Daisy wheel
 Line printer
 Braille printer
 Chain printer
 Drum printer
Non-impact printers
These are printers whose printers heads do not come in contact with the paper (print
media) while printing i.e. they are using spraying mechanism (ink) to create images.
Examples of non-impact printers
 Ink jet printers
 Laser printers
 Mobile printers
 Bubble jet printers
 Xerographic printer

Differences between impact and non-impact printers

Impact printers Non-impact printers
They are slow They are very fast
Impact printers are noisy Non-impact printers are quiet
Impact printers are cheap Non-impact printers are very expensive
Their printing mechanism is physical They use spraying mechanism

Advantages of impact printers

 They are cheap to acquire
 They can produce many copies at the same time
 Impact printers can withstand dusty environment

Disadvantages of impact printers

 They are generally noisy because of striking mechanism.
 The print quality is not as good as the non-impact printers
 They have a slower speed compared non-impact printers

Advantages of non-impact printers

 They can produce high quality colour output
 Inkjet printers are generally quiet than dot matrix
 They are faster in data processing.

Disadvantages
 They are very expensive to acquire
 They need specialized papers to produce high quality output.

Plotter
It is a high quality printer that generates drawing
e.g. poster, maps, sign posts, bill boards.
 Differences between screen output and print output

Screen output Print output

Display soft copy output Prints out hard copy
The output is temporal i.e. it is lost The output permanent i.e. it can be
when power is off obtained for future use
Silent output Noisy output especial for impact printers
Very fast Very slow

Ports
A port is a socket on the outside of the system unit that is connected to an expansion board
inside the system unit. A port allows you to connect a peripheral device such as a printer,
scanner etc so that it communicates with the computer system.
Parallel ports
This allows lines to be connected that will enable 8bits to be transmitted simultaneously.
Parallel ports are used mostly for connecting the printers.

Serial ports
Serial port enables a line to be connected that will sent bits one a time on a single line.
Serial ports are used for communication line like modems.

USB (universal serial bus port)

USB is a type of port that allows you to connect several different devices using only one port
e.g. you can use a USB port to connect a printer ,scanner etc to your computer e.g. mice
,keyboard.

Video adapter port (VGA)

These are used to connect the video display monitor outside the computer to the adapter
card inside the system unit.

Game port
Game port allows you to attach a joystick or similar game playing devices to the system
unit.

System unit
This is a case or cabinet that houses internal parts of the
computer.

The following are the internal parts of the computer;

Motherboard
Hard disk
RAM
CMOS battery
Expansion slot
CPU video card
NIC (network interface card)
Power supply
ROM
CPU fan
Bus lines

Power supply
This is the device that supplies power to the computer
system. It converts electricity coming from the wall to the
lower voltage which a computer can use.
 Expansion slot
These are sockets design on the circuit board for other
devices such as video cards and sound card. Are sockets on
the motherboard onto which you can plug expansion cards
(peripherals).

Expansion cards
This is a circuit board that provides more memory or
control peripheral devices.

Motherboard
It is circuitry board of a computer where all the other
devices are connected.

Bus line
This is an electric pathway through which bits are transmitted within the CPU and other
devices in the system unit.

Bus line is classified into three namely;

 Data bus
 Address bus
 Control bus
Data bus
These are internal channels that carry data between the computer CPU and its RAM
together with input and output devices.

Address bus
This is an internal channel from the CPU to the main memory across which the address of
data is transmitted.

Control bus
This is a computer bus that is used by the CPU to communicate with the devices that are
contained within a computer system.

Networking devices /data communication

Networking hardware / network equipments are devices that facilitating the use of
computer networks by enhancing the transmission, controlling the direction of data packets
or extending the size of the network.

Examples include;
 Nic (network interface card)
 Repeater
 Switch
 Hub
 Router
 Gateway
 Bridge
 Modem
 Multiplexer

Nic (network interface card)

To physical connect a computer to a network, the
computer must have NIC .NIC is a piece of computer
hardware that allows computer to communicate
over computer network. It is also called network
adapter.

Repeater
Since a signal loses strength as it passes a
long cable, it is often necessary to boost the
signal with a device called a repeater. The
repeater electronically amplifies the signal
it receives and rebroadcast it. They are used
when the total length of your network cable
exceeds the standard set for the type of
cable being used is (100m).
Hub
This is an electronic device used to interconnect
multiple hosts to a network. A hub can’t decode a
data packets or message sent from one host to
another through it but instead duplicate that
message to all hosts connected to a network.

Switch
This is a networking device used to interconnect multiple hosts computer and other devices
like printers to a network. During data exchange between the network hosts, switch
receives data packets from the sending host, decodes it to find out the destination or host
and forward the packets to the exact target host.

Gateway
This is a device configure to provide internet.

Bridge
This is a networking device used to break down a large
network into smaller, smaller networks with the aim of
improving its efficiency.

Router
This is an electronic networking device that connects a LAN
to other local area networks LAN as well as controlling
traffic between them.

Modem
This is a communication device used to convert analogue signals into digital signals and vice
versa.