INPUT UNIT: This comprises of keyboard, mouse and
scanner
i. The Keyboard
The keyboard is a tool that is used for
typing like a typewriter. Of course, it has more functions than the typewriter.
Different keys on the keyboard perform varying functions and include;
A Standard
Keyboard
1.
Alphanumeric
2.
Control keys
3.
Cursor keys or arrow keys
4.
Numeric keys
5.
Function keys
Alphanumeric Keys
As the name implies, alpha refers to
alphabet and numeric refers to number. Alphanumeric contains both alphabet and
numbers. Alphabet are A-Z, and numbers 0-9. apart from alphabet and numbers
other keys are associated with these type of keys and include; Shit, Enter,
Space, Caps lock, Tab Back space keys.
Functions
Keys
These are
additional keys on the key board for special usd under operating system and
application programs. The keys contained here are F1, F2, F3, F4, F5, F6, F7,
F8, F9, F10, F11, and F12.
Numeric
Keys
Found at the
right hand side of the keyboard, the numeric keys are numbered 0-9 and are used
when input are in their numeric form.
Control
Keys
Control keys
do not have a specific place on the keyboard. They are found on the
keyboard and include; Insert, delete,
end, Esc, Print Screen, Scroll Lock, Pause, Home, Page Up, Page Down, Control,
Alt, and Num Lock.
Also known as
the arrow keys the cursor keys help moving the cursor up, down, left and right
side on the screen during operation.
THE MOUSE
A mouse is a
small hand held device used to control the pointer on the screen. It is
connected to the system unit. Mouse shows arrow pointer on the monitor screen
for selecting required command from menu rather than typing by using keyboard.
When you turn over your mouse you will see a small ball. When you move your
mouse over a flat surface the ball rotates. A sensor picks up the movement of
the ball, and translates this into movement of the pointed arrow on the screen.
You can click, double click, drag and drop and right click on the mouse.
THE SCANNER
Scanner is a machine that you can use
it in your computer works. It uses laser beans and reflected light to translate
drawing, photos and even text into digital form. These images can then be
processed by a computer, displayed on monitor, stored on a storage device or
communicated to another computer.
(C)OUTPUT UNIT
An output unit is a medium through
which all processed or computed results are made out for the user. This result
could either be soft copy output or hardcopy output. A soft copy output is the
result displayed on the monitor. It is referred to as the information displayed
on a screen or in audio or voice form through speakers. It is said to be a
temporal output Hardcopy output is said to be permanent. It refers to output
printed on paper. We shall now take a look at the output devices.
SOFTCOPY OUTPUT DEVICES
Monitor
Monitor also called display screen or
visual display unit (VDU), are the main means of softcopy unit. Screens are
large range from 14 to 21 inches. The screen is coated with phosphor on the
back. An electron gun shoots electrons at the back of the screen, creating a
glow where they hit. The stream of electrons can be controlled to produced
whatever images needed. There are two types of display screens. These are
Cathode Ray tubes (CRTs) and Flat-panel displays.
Cathode Ray Tubes
A careful watch at the television
screen gives you an idea of this display
screen. The images are represented on the screen by individual dots called
pixels. A pixel is the smallest unit on the screen that can be turned on and
off or coloured in different shades. The number of pixels determines the
resolution on the screen. Resolution here refers to clarity or sharpness of an
image when displayed on the screen. Computer aided design (CAD)packages require
screen with high resolution so that design can be viewed and worked on in great
detail.
Flat Panel Display Screen
These are mainly used on portable
computers like laptops. They consist of two pplates of glass with a substance
in between them that creates the image on the screen. The different types of
flat screen are liquid crystals display (LCD), electroluminescent display (EL) and
gas plasma display (GPD).
HARDCOPY OUTPUT DEVICES
Printer: These are output devices used to
obtain report after processing. It puts things from the computer into papers
varying printers do exist but the common ones are LaserJet, Inkjet and
Dox-matrix.
LaserJet Printer: The operation of Laser is similar to
photocopying machine. It incorporates the use of laser beam, a mirror and a
rotating drum to print characters on papers. The output here is of high quality
but slow in speed.
Inkjet Printer: The quality and speed of an inkjet
printer are both slow. Printing is achieved by spraying jets that are able to
dry.
Dot-Matrix: It prints by creating
characters in form of tiny dots. It achieves this by impact. The printer head
contains some tiny pins that hit the ribbon to form characters on the paper. It
is slow and noisy
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