COMPUTER HARD WARE
What is computer hardware?
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Examples of computer hard ware
– Mouse
– Keboard
– Plotter
– Printer
– Monitor
– Hard disk
– Random access memory
– CPU
Category of computer hardware
Computer hard ware are categorized as input device, output Device, storage device and
processing component of a computer

Input device what are they?
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Examples of input device
-Mouse
-Digital Camera
-Light pen
-Scanner
-key board
-bar code reader etc

Factors that determine the quality of a scanner.
1) Resolution—sharpness and clearness of an image.
2) Colour depth– number of bits used to store information about each pixel.

Qn1. Give two advantages of using an automatic input device (e.g., a OMR reader) over
manual input.
1) Faster than manual input.
2) Less chance to get errors during the input process.
Qn2. Give two advantages of using a barcode reader at a point of sale terminal (POS).
1) The process of data entry is fast and accurate.
2) Bar codes can be printed by normal printing methods
Output device what are they?
Examples of input device
Qn3. Give two advantages and two disadvantages of using voice recognition for input.
Advantages:
1) No typing of data is necessary.
2) Can be used remotely by telephone or by people whose hands are occupied or disabled.
Disadvantages:
1) Error rate is high and recognition of words is slow.
2) Not suitable for use in noisy places.
Qn4. Give two real life applications of sensors for detecting external changes in an
environment.
1) Freezers and chiller cabinets in supermarket to monitor temperature.
2) Alarm systems that detect light, pressure or movement.
Qn5. What is a dumb terminal? Give two examples of a dumb terminal.
A dumb terminal is a device with a keyboard and a monitor but has no processing power.
Examples:
1) Automated teller machines (ATM)
2) Point of sale (POS) terminals
Qn 6.Give six examples of input devices and six examples of output devices on a desktop
computer.
Input devices:
1) Keyboard

2) Mouse

Output devices:
1) Monitor
2) Digital Projector
3) Speaker
4) Printer

Monitor (screen)

Monitor (screen) ( LED,LCD,CRT)
Advantages of a LCD monitor over a CRT monitor, and the advantages of a CRT
monitor over a LCD monitor.
Advantages of LCD monitor over CRT monitor:
1) require less power and desk space.
2) Radiation emitted by LCD monitors is neglectable.
Advantages of CRT monitor over LCD monitor:
1) Can be viewed from a wide variety of angles.
2) Can produce fast and rich color output.
QN1. Give two advantages and two disadvantages of display devices (e.g., a monitor).
Advantages:
1) The time to display the image is fast.
2) Display devices are usually quiet.
Disadvantages:
1) Information produced is only temporary, and will be lost when the power of the
display device is turned off.
2) Unsuitable for users with visual problems.

A peripheral.

A peripheral is an external device attached to the system unit of a computer.
Examples:
1) Keyboard 2) Printer

PRINTER
What is a printer?
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Types of printers
– Dot-matrix printers eg Epson Lx 350
-laser printers eg HP p1102,M35H etc
– Inkjet printers eg HP Deskjet 250
Laser printer Advantages
– Fast output
-Relatively quiet
-Cheap to buy compared to dot matrix printer
Laser printer disadvantages
– More expensive running costs than dot matrix
Inkjet printer advantages
– Faster output than dot matrix printer Relatively quiet compared with dot
matrix printer
– Cheap to buy
Inkjet printer disadvantages
-Ink more expensive than dot matrix Ink needs changing regularly on long
print runs
-Difficult to print a sealed secure payslip
Dot matrix printer advantages
– cheaper running costs
-Continuous paper feed available
-Can print multi part forms
– Can print through a payslip cover
-Can produce carbon copies
-High quality is not needed when printing payslips
Dot matrix printer Disadvantages
-More expensive to buy
-Noisy
– Relatively slow
Qn1 Give two advantages of dot-matrix printers over laser printers and inkjet printers.
Advantages of dot-matrix printers:
1) Can print multi-part forms.
2) Can withstand dusty environment, vibrations, and extreme temperature.
Qn2 .Give two advantages of printers over display devices, and then give two advantages of
display devices over printers.
Advantages of printers over display devices:
1) Information produced is more permanent.
2) Multiple copies can be obtained.
Advantages of display devices over printers:
1) Can generate output quickly and quietly.
2) No paper is wasted for producing the output

A multifunction device;

These are devices that perform many function such as printing,
scanning and photocopying
Qn3.Give one advantage and one disadvantage of a multifunction device.
Advantage:
Normally less expensive than purchasing each device separately.
Disadvantage:
If the machine breaks down, the user loses all its functions.
Qn4. Suggest one output device for each of the following tasks:
a) To print a high volume of hard copies.
b) To print a colour photograph at home.
c) To print multi-part forms in a department store.
d) To print a large-size architectural drawing.
e) To produce music or voice output.
Solution
a) Laser printer
b) Colour inkjet printer
c) Dot-matrix printer
d) Plotter or large format printer
e) Speaker
what is storage media
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Examples of storage Medea
 Optical disk eg CD ROM ( compact Disk Read only Memory)
 DVD ROM ( Digital Versatile Disk Read only memory)
 Flash Disk
 Hard Disk
 Floppy Disk
 Magnetic Tape
Storage device what are they?
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Examples of storage device
Floppy disk drive
2) Hard disk drive
3) Optical disk drive (e.g., CD-ROM drive)
4) Tape drive
Secondary storage what are they?
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Reasons why secondary storage is necessary.
1) Memory (i.e., primary storage) is volatile but secondary storage is nonvolatile.
2) Secondary storage is cheaper and provides larger storage capacity.
Questions
Suggest one suitable input device for each of the following tasks:
a) To enter instructions in a command line user interface.
b) To move the pointer in a graphical user interface.
c) To input text or graphics from hard copies into electronic format.
d) To convert characters from graphic format back to editable text format.
e) To mark multiple-choice type answer sheets in an examination.
f) To process cheques in a bank.
g) To read the bar codes of products in a supermarket.
h) To record human voice into the computer.
Solution
a) Keyboard
b) Mouse
c) Optical scanner
d) Optical character recognition (OCR) reader
e) Optical mark recognition (OMR) reader
f) Magnetic ink character recognition (MICR) reader
g) bar code scanner
h) Microphone

Processing component

Processing component what are they?…………………………………………………………………………………………..

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Examples of processing component.
 CPU (Central processing Unit)
What is CPU?
PART OC CPU
– ALU

ALU
The three operations carried out in the ALU are:
1) Arithmetic operations, which include addition, subtraction, multiplication, and
division.
2) Comparison operations, which involve comparing one data item to another, and
determine if the first item is greater than, equal to, or less than the other item.
3) Logical operations, which work with conditions and logical operators such as AND,
OR, and NOT.
Register
Registers are high-speed temporary storage locations used to hold data and
instructions.
Two kinds of registers in the CPU. Examples:
1) Program counter, which holds the address of the next instruction to be fetched from
the memory.
2) Accumulator, which holds the data item to be processed and the results of arithmetic
and logic operations.

– Control Unit

The control unit (CU) is a component of a computer’s central processing unit (CPU) that directs the operation of the processor.

BUS
–Bus ( path or channel for transfer of information)
What is a bus ?…….
Data bus transfers actual data.
Address bus transfers information about where the data should go in memory
A system bus connects the CPU to memory.
An expansion bus allows the CPU to communicate with peripheral devices.

Memory
–Random access memory (RAM)is a volatile memory which loses data if power goes off.
Volatile memory loses its contents when the computer’s power is turned off. e.g., RAM
Nonvolatile memory does not lose its contents even when the computer’s power is
turned off. e.g., ROM
Qn 1
a) Describe two differences between RAM and ROM.
1) RAM is volatile, but ROM is nonvolatile.
2) RAM can be read and written, but ROM is read-only.
b) How does memory cache speed the process of computing?
Memory cache speeds the processes of computing by storing frequently used instructions
and data