Ch-3 INPUT / OUTPUT DEVICES

INPUT DEVICES

Computer users are used to these devices to enter some data or instruction to computer. As we can say these devices are the source of communication with computer.

KEYBOARD
Keyboard is one and important input device. Keyboard is a main input device, which is used to enter data / instruction to computer. A normal Keyboard has 104 keys. A Keyboard consists of four different types of keys.

1. Alphanumeric keypad
The main part of the keyboard consist these keys, which is normally used for typing purposes. Alphanumeric keys also divided into three parts.

a. Alphabet Keys:- there are 26 alphabet keys from A to Z in both cases (upper and lower)
b. Numeric Keys:- there are 10 numeric keys used from 0 to 9
c. Punctuation:- space bar, !, ~, `, +, - (, ) *, & , ^, %, $, #, @ are punctuation keys.

2. Numeric keypad
On the right side of the keyboard there are some numeric keys from 0 to 9 with some arithmetic keys + - / *, point, Num lock and Enter keys are used for numeric purpose.

3. Function Keys
On the top of every keyboard there are some keys from F1 to F12 performed some function. Function keys perform different function in different Computer Programs.

4. Special Keys
In keyboard there are some special keys used for different purposes i.e. Esc, Tab, Ctrl, Shift Key, Alt key, Backspace, Enter, Caps Lock, Insert Key, Delete Key, Home Key, End Key, Page Up/Down and Arrow Keys etc used for different purposes.

MOUSE 
A common pointing device. The basic features of a mouse are a flat-bottomed casing designed to be gripped by one hand; two or three buttons on the top; a cable connecting the mouse to the computer. By moving the mouse on a surface (such as a desk top), the user typically controls an on-screen cursor. To select items or choose commands on the screen, the user presses one of the mouse's buttons, producing a "mouse click."

1. Pointing: When you move the mouse on the pad, you are actually moving and pointing the cursor on the screen.

2. Clicking: Press the left button of the mouse is called clicking. Single click used for selection and double click used for running the program.

3. Dragging: To continue to hold down the mouse button as you move the mouse is called dragging the mouse.


JOY STICK
A pointing device used mainly but not exclusively for computer games. A joystick has a base, on which control buttons can be mounted, and a vertical stem, which the user can move in any direction to control the movement of an object on the screen; the stem may also have control buttons.


SCANNERS
Scanner is an input device, which scans image of a picture or text and saves it in the computer with the help of software. The image in converted into signals, which the computer understands. There are two types of scanners Flatbed and Handy.



TRACKBALL
A pointing device that consists of a ball resting on two rollers at right angles to each other, which translate the ball's motion into vertical and horizontal movement on the screen. A trackball also typically has one or more buttons to initiate other actions. A trackball's housing is stationary; its ball is rolled with the hand.

ELECTRIC LIGHT PEN
An input device consisting of a stylus that is connected to a computer's monitor. The user points at the screen with the stylus and selects items or chooses commands either by pressing a clip on the side of the light pen or by pressing the light pen against the surface of the screen. Light pen is use with a special monitor. It consists of a photocell placed in a small tube. Which can selecting, editing etc. Light pen is used in graphics.

MIRCROPHONE.
A device that converts sound waves into analog electrical signals. Additional hardware can convert the microphone's output into digital data that a computer can process; for example, to record multimedia documents or analyze the sound signal. With the help of microphone we can store our voice in computer just like type recorder. Microphone runs on multimedia software.

VOICE RECOGNITION
An input device that translating voice to text with the help of a special software. With the help of this device a user give dictation to computer, and computer type this dictation automatically. Also a user can control the computer with vocal commands such as open file, save file, shutdown etc. But it is necessary when you installed the software, you need a good practice.

DIGITAL CAMERA
This is a special type of camera attached with the computer and used by a special software. By this camera, picture of some things is obtained and saved in the computer. It sends it directly to the attached computer.

DISKDRIVE

In computer the disk drive used for input and output purposes. The disk drive is used to read and write data or information from disk that use heads for these purposes. There are different types of disk drive are Floppy disk drive, CD-ROM drive, ZIP drive etc.

OUTPUT DEVICS

These devices are used to produce process data or instruction from computer in form of information. The most common devices, which are used for these purposes, are Monitor and Printer.

MONITORS

The device on which images generated by the computer's video adapter is displayed. The monitor is attached to the video adapter by a cable with system unit. Monitor is one and important output device. There are different types of monitor are used.

1. Monochrome monitors: - this is a two colors (black & white )monitor.
2. CGA:- Color Graphic Adapter is a popular monitor (4colors).
3. EGA:- Enhanced Graphic Adapter. Display upto 16 colors at the same time.
4. VGA:- Video Graphic Array to display 256 colors at one time.
5. SVGA:- Super Video Graphic Array display to 256 & more colors. But the colors are much sharper and clear.