Input and Output Devices

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.

Cursor Keys

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