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Components of Computer Hardware: are the parts of a computer that makes up the hardware.

They are: CPU, Input Devices, Output Devices and Storage Devices.

1. Central Processing Unit (CPU) of Microprocessor
The CPU located on your computer’s main circuit board (Motherboard)
is basically the brain of your PC. The CPU may either consist of a single
chip of series of chips that perform two main functions. The first of
these functions is to perform arithmetic and logical calculation, while the second function is to time and control the operations of the other elements of your computer.

2. Input Devices
Computer operators communicates with the computer’s CPU by using various input devices to enter data, run programs, or give commands to the CPU. 
These devices include the following:
Keyboards
The keyboard uses a key arrangement similar to that of an ordinary
typewriter, with the addition of some special function keys and a
numeric keypad.
Mouse
When using a mouse, one is able to move the cursor around the screen
with speed and simplicity. Most have two buttons, which will execute
commands according to an application’s control instructions.
Scanners
A scanner reads information from paper, and transfers this as text or
graphics onto a PC where it is stored and can be edited.
Internal Modems
Modems are expansion cards or external units, which send information
from one PC to another via the telephone cables. A modem is necessary
if you wish to have access to the Internet.
Light Pens
A light pen transfers graphics information from electronic pads into the
computer.
Voice
Voice recognition software translates the spoken word into digital
signals, which the computer understands.
Joystick
Similar to a mouse, the joystick also translates physical motion into
motion on a computer video display screen.

3. Output Devices
We have briefly looked at how we put information in the computer with
the use of various input devices. Now let’s look at how the computer
communicates with us.
Monitors
The most common output device used with a desktop computer is the
monitor, which is used to display characters and graphics on a screen
similar to that of an ordinary television set. Smaller portable computers,
such as notebooks and laptops, use liquid crystal display (LCD) screens.
Modem
A modem links two or more computers by translating digital signals into
analog signals so that data can be transmitted via telephone lines.
Printers
Another standard output device is the printer. Printers provide us with a
paper copy of the PC’s result. Various types of printers are available in
the market place. Some of there are listed below.
Dot-matrix Printers
Dot-matrix printers have a set of pins, which impact upon the ribbon
against the paper, producing varying qualities of print. Modern dotmatrix
printers are capable of fairly high quality printout at high speed
and are used for the end product in a wide range of commercial
environments.
Ink-jet and Bubble-jet Printers
These printers are a successful compromise between dot-matrix and the
much higher laser printer quality. It may be as small as and not much
more expensive than the dot-matrix printer. The quality is much higher
and as an almost silent printer, it has gained enormous popular demand.
Laser Printer
Offering very high resolutions, laser printers suit a wide range of
business and media-oriented applications. They are expensive, but often
more economical when speed, durability and professional print quality
are considered. Laser printers produce extremely high-resolution
graphics. Colour options are available, but at a high cost.

4. Storage Devices
Computers can store data either internally (in memory) or externally (on
storage devices)
Internal Storage
There are two areas in a PC where instructions and data can be
temporarily stored called memory. The first type of memory is known
either as RAM (Random Access Memory) or as DRAM (Dynamic
Random Access Memory) while the second type is known as ROM
(Read Only Memory).
-RAM
RAM comes in the form of silicon memory chips called SIMM’s which
are mounted directly on the computer’s main circuit board or in chips
mounted on peripheral cards that plug into computer’s main circuit
boards. RAM chips consists of switches that are sensitive to changes in
electric current. RAM chips hold their stored information of data as long
as the circuits receive a constant current flow. The data is lost if the PC
is switched off.
RAM chips are upgradeable, that is, can add more.
-ROM
ROM chips are also made of silicon. However, all of the switches on
these chips are already set. The patterns on the ROM chips form
commands, data, or programs that the computer needs to function
correctly.
External Storage
External storage devices, such as a hard disk, can physically reside
within the computer’s casing. However, the drives remain external to the
main circuit board. Some of the external devices are listed below.
Hard Disk
The most common external storage device used in a PC is the hard or
“fixed” disk. Hard disks are usually fixed in their disk drive cabinets,
which contain the electronics needed to read and write data onto the
disks’ magnetic surfaces. Hard disks cannot be removed.
Removable Disks
As the hard disk is usually a permanent fixture inside the PC’s casing,
removable disks were originally used to make a copy of information
(back-up) or transfer information from one unit to another. The most
common removable disk at present is known as a Stiffy Disk.
CD-ROM
Data may be stored on a CD-ROM. The same technology is used as the
laser techniques that are used to create audio compact disk. In order to
store on a CD-ROM you require a special devices known as a CD-ROM
writer.
Magnetic Tapes
High-speed tape drives are used to copy data and information from the
hard disk onto removable tapes. The process of copying data from one
type of storage device to another is known as “backing up”. The storage
capacity of a magnetic tape far outweighs that of a stiffy disk and is thus
popular when backing up hard disks

Credits: NOUN
Source: http://www.nou.edu.ng/uploads/NOUN_OCL/pdf/SST/CIT%20101.pdf  .

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