COMPUTER HARDWARE AND SYSTEM STARTUP
Computer hardware
Hardware refers to any physical/tangible part of the computer that you can touch, feel, see and pickup.
Classification of computer hardware
1) Input devices 4) Storage devices
2) Processing devices 5) Communication devices
3) Output devices
Input devices
Computer input refers to any data and instructions entered/fed into a computer for processing.
Computer input devices are components/devices that enable a user to enter/feed data and instructions
into a computer for processing.
The two types of computer input are:
1. Data
2. Commands
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Examples of Input devices
1. Keyboard 8. Scanner 14. Touch screen
2. Mouse 9. Digital camera
3. Touchpad 10. Bar code reader
4. Trackball 11. Digital video camera
5. Stylus and graphics tablet 12. Web camera
6. Joystick 13. Magnetic stripe recognition
7. Microphone
a. KEYBOARDS
Keyboards are used to input text, numbers and instructions into the computer.
Uses of the keyboard
1) Used to input data into applications
2) Used to enter commands into the computer
b. MOUSE
A mouse: is the most widely used pointing device on personal computers.
Pointing: devices are part of hardware used to control a pointer (cursor) on a screen.
There are three different types of mice:
1) A mechanical mouse uses a ball underneath to detect movement
2) An optical mouse uses light to detect movements
3) Cordless mice use wireless technology to detect movements
Mice have two buttons and a scroll wheel. These provide users with different functions:
Left button: is used to select icons and click options
Right button: is used to call up a drop-down menu of options
Scroll wheel: is used to move up and down through a document.
Uses of the mouse
1) Opening, closing, maximising and minimising programs and files.
2) Moving, grouping and deleting files.
3) Controlling a pointer on screen to select icons or move around the page.
4) Editing images in terms of size and position on the screen.
Major problems that often affect the proper functioning of the mouse
1) Dirt disrupts motion of the ball in the mechanical mouse
2) Nature of the surface-not too rough or too smooth
3) Disconnection of the chord in case the mouse falls down
4) Connecting the mouse to the system unit one must be very careful to follow the directions of the pins
c) Touchpads: These are normally found on laptops and users brush their finger over the touchpad in
order to control a pointer on the screen.
SCANNERS: Scanners are used to enter information on paper (hard copies) into a computer. Scanners can
convert hard copies (printed documents, photographs) into digital data.
Uses of Scanners
1) Used to scan hard copy / printed documents into a computer.
2) Old photos and important documents (like birth certificates) can be scanned into the computer. This
means you still have a copy if the original is damaged or lost.
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WEB CAMERAS (WEBCAMS): Web cameras can capture both digital images and video that are sent over
the internet.
Uses of Web Cameras:
1) Used to conduct face-to-face conversations with friends and family on the internet.
2) Used to hold video-conferencing meetings over the Internet.
3) Can capture image and video content for presentations and web sites
4) Some people use web cams as a cheap alternative to security cameras.
The main processing hardware includes:
1) Central processing unit (CPU)
2) Main memory
Central processing unit (CPU) microprocessor/microchip: The CPU is the brain of a computer responsible
for performing all the processing activities within the computer.
Functions of the CPU
1) Processing data
2) Fetching and sending of commands and instructions
3) Performs arithmetic and logic operations
4) Temporary Storage/holding of data, instructions and results during processing
Types of computer memory
Computers use two basic types of internal memory:
Read only memory (ROM): ROM has contents that can be read but cannot be written to during normal
computer operations.
Random access memory (RAM): RAM is used to store programs being used by the user when the computer is
working.
Differences between RAM and ROM
RAM ROM
1) Volatile Non volatile
2) Read and write Read only
3) Temporal Permanent
4) Can be increased Normally not increasable
READ ONLY MEMORY (ROM)
ROM is used to permanently store instructions that tell the computer how to boot (startup). These instructions
are known as the BIOS (Basic input/output system)
Information stored in ROM is known as READ ONLY. This means that the contents of ROM cannot be altered
or added to by the user.
ROM is Non-Volatile memory. This means that stored information is not lost when the computer loses power.
Contents of the read only memory are collectively called firm ware that is set during manufacture and cannot be
altered.
ROM is the smallest in size and contains programs that are built in during manufacture.
TYPES OF READ ONLY MEMORY
PROM-programmable read only memory: Programmable read-only memory is memory on which data
can be written only once. Once a program has been written onto a PROM, it remains there forever.
EPROM- erasable programmable read only memory: Erasable programmable read-only memory can be
written to only once and erased once for new contents to be stored and cannot be erased any more.
EEPROM-electronically erasable programmable read only memory: Instructions can be put in this
memory as many times as one may like. The memory contains instructions up to when one decides to alter
them.
Uses of ROM
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1) ROM stores data and programs that must be kept permanent
at all time
2) ROM stores system files that enable a computer to operate
3) ROM stores BIOS that enables a computer to start
RANDOM ACCESS MEMORY
RAM is used to temporarily store information that is currently in use by the computer.
RAM can be read from and written to and so the information stored in RAM can change all the time (it depends
what tasks you are using the computer for).
RAM is a fast memory. Data can be written to and read from RAM very quickly.
RAM is Volatile Memory. This means that information stored in RAM is deleted as soon as the computer is
turned off.
RAM forms a major portion of main storage and is in constant use for temporary storage.
Uses of RAM
1) Provides storage of a copy of the system software program.
2) Provides temporary storage of a copy of an application program
3) Provides temporary storage of a copy of data items input from the key board and mouse.
Secondary storage media is categorized under:
1) Magnetic storage devices
2) Optical storage devices
3) Solid state storage devices
Magnetic storage devices
Hard disk drive Zip disk drive
Floppy disk drive Jaz disk drive
Magnetic tape drive
Optical
storage devices
1. CD-R drive
2. CD-ROM drive
3. CD-RW drive
4. DVD-R drive
5. DVD-ROM drive
6. DVD-RW drive
Solid state storage devices
Memory cards Flash disks Solid state hard disks
Types of hard disks
Internal (fixed) disks: These are high speed and high storage capacity hard disks that
cannot be removed from the disk drives.
External (removable) hard disks: These are special types of hard disks that may be
inserted in the computer when there is need for storage and then removed thereafter.
Uses of external hard disks
1) Can carry data-backups all over the place
2) Transfer information, programs and pictures between computers
Advantages of external hard disks
1) Improved data cargo carrying capacity
2) More portable-small and light
Disadvantages of external hard disks
1) Have to be handled quite carefully
2) More expensive than other forms of
removable storage.
3) Easy to be stolen or misplaced
Removable storage media: Removable media is any type of storage medium that can be
removed from a computer and is not incorporated into the computer itself. Examples of
removable media include CDs, DVDs and Blu-Ray disks, as well as diskettes and USB flash
disks.
Compact disks: Compact disks are the most widely used optical disks formats. Compact disks
are flat, round, portable storage medium that store data using light beams. Compact disks are
mostly used to store data and information such as video clips, software and sounds. CDs have a
maximum storage capacity of 700MBs
Digital versatile disks (DVDs): DVDs are also called digital video disks. With these disks, more
data can be packed on the disk. DVDs are suitable for recording motion pictures such as video
because they offer better sound and picture quality. DVD-ROMs have a storage capacity of
4.7GB
Difference between CDs and DVDs
1) DVDs have higher storage capacity than CDs
2) DVDs are cheaper per unit data storage
3) DVDS guarantee higher quality features (sound and video)
4) CDs are cheaper (cost) than DVDs
5) Reading and writing CDs is faster than on DVDs
Variations of CDs and DVDs
1) CD-ROM and DVD-ROM
2) CD-RW and DVD-RW
3) Blu-Ray disks
4) CD-R and DVD-R
CD-ROM and DVD-ROM: These disks have data that cannot be written over (added to) but
can only be read. These disks are bought with pre-loaded data already on them. Whatever is
already loaded onto the disk cannot be removed or changed. DVD-ROMs hold large amounts of
data like movies, modern games, and multimedia encyclopedia.
CD-Rs and DVD-Rs: These disks are bought blank and data can be added to the disk (once) but
not removed when it is on there. These disks are ideal for single burning or recording of data.
CD-RWs and DVD-RWs
Data can be added to these disks and also be erased over and over again. Are also called erasable
disks and are ideal for applications that require updating of information and ability to record over
old data.
Forms of computer output
1) Soft copy
2) Hard copy
Soft copy:
Soft copy refers to information/data displayed visually on the screen or is audio or voice form
such as speech or music and this kind of output is not tangible. Soft copy exists electronically
and displays for a temporary period of time.
Hard copy:
Hard copy refers to information/data that is in a permanent form that is in print out form. Hard
copy is tangible. Hard copy is considered hard because it exists physically on paper, whereas a
soft copy is considered soft because it exists only electronically.
Examples of output devices
1) Monitors
2) Speakers
3) Data Projectors
4) Printers
