Input Devices
The devices through which data are input to computer are called input devices of computer. The main input devices are Keyboard, Mouse, Scanner, Joystick etc.
Keyboard
Keyboard is an input device. It enables users to enter data into a computer. Computer keyboards are similar to typewriter keyboards but contain additional keys. When the user types a character, electronic circuits in the keyboard translate into bit charges. They travel to a buffer, the when they appear in the buffer, and processor sends it to the RAM. At the same time, the processor instructs the monitor to put the character on the screen.
Keyboard consist the following keys.
· Alphabetic keys.
· Numeric keys.
· Function keys.
· Control keys etc.
· XT ( Extended keyboard ) : 85 keys
· AT (Advanced keyboard) : 101 keys
· Enhanced keyboard : 103 or more keys
Mouse
A mouse is a pointing device it is held in one hand and move across a flat surface. A mouse may have two or three buttons. Mouse is one of the most widely used input devices of the computer. We can select the command draw pictures, edit text etc by pressing the mouse button.
Type of mouse
· Mechanical Mouse
· Optical Mouse
One type of mouse has a round ball under the bottom of the mouse that rolls and turns by wheels which control the direction of the pointer on the screen. This is called mechanical Mouse. Another type of mouse uses an optical system to the track the movement of the mouse. This is called optical mouse. Laptop computers use touch pads, buttons and other devices to control the pointer.
Scanner
Scanner is a device that optically scans images, printed text, handwriting, or an object, and converts it to a digital image. The resulting image can be stored in a file as Bit Map or JPEG (Junction photographic exports Group), displayed on a screen, and manipulated by programs. User can not directly edit text that has been scanned.
Light pen
It is a pointing device which is very sensitive to light. It uses a light sensitive cell to communicate the screen position to computer. When the light pen tip is placed a gains the screen, it is capable of sensing its position or CRT. As the tip is moved over surf face of screen, its light sensitive element detects the light emitted from screen. We can select the desired option of menu by touching light pen against desired option.
OMR ( Optical Mark Reader)
OMR is an input device which can read marks such as pencil marks on a page. It is used to read forms and multiple- choice question pagers. The marks are then exposed to beam of light for sensing and optical mark reader scores the test by identifying the position of mark.
OCR (Optical Character Reader)
An OCR detects alphanumeric characters printed or typewritten on paper. It may be handled scanner or a page scanner to detect light reflected from a line or from a page of the text. The change in the reelected light is converted to binary data which is sent to the processor. The illuminated by low-frequency light source. The light is absorbed by areas while the light is selected from light areas.
BCR (Bar code Reader)
This method uses a number of bars (lines) of varying thickness and spacing between them to indicate the desired information. A bar code reader can read such bars and convert them into electrical pusses to process by a computer. The bar-code detects as ten digits. The first five digits identify supplier or manufacturer of item and second five digits identify individual product.
Touch pad
When you want to click, you can tap pad or use the buttons in front of pad, which works like mouse buttons you move your finger on the pad o move the cursor on the screen. Many laptop computers use a touch pad of keyboard.
Microphone
It is an input device of computer it is used for recording voice and sound. It is mainly used for voice mail, video chat, conferencing etc.
Digital camera
A digital camera is a camera hat takes video or still photographs, or both, digitally by recording images via an electronic image sensor. Most 21st century cameras are digital it stores thousands of images on a single small memory device and deleting images to free storage space. The majority including most compact cameras, can record moving video with soured as well as still photographs.
Joystick
A joystick is also pointing device. It is used to move the cursor on a CRT screen A Joystick is a stick which has spherical ball at its lower end as well as upper end. The lower spherical ball moves in a socket. The Joystick can be moved right or left, forward or backyard. The electronic circuitry inside the joystick detects and measures the displacement of the joystick from its central position, the information is sent to the processor jousting is used in games.
MICR (Magnetic Ink character Reader)
It is an input device which uses a magnetic ink reader to recognize character printed with a special magnetized ink (i.e. iron oxide particles) used to write characters on the cheques and deposition forms which are to be processed by an MICR. To identify the characters these patterns are compared with special pattern stored in the memory. Before cheques are issued to customers the identification number of the bank and depositor‟s account number are printed on the lower left-side of the cheques with magnetized ink. When the cheque is entered into an MICR, it passes throng a magnetic field.
The read heads reads the characters written on the cheque with magnetic ink. It interprets the characters and sends the corresponding data directly to computer.
Touch Screen
Touch screen enable the user to select an option by pressing a specific part of the screen with finger. A matrix of beams over the screen in the horizontal and vertical dimensions. If the beam is interrupted by a finger, the position is determined by the interrupted beams. In an alternative version of touch screen, the display is covered with touch sensitive surface. The user must contact with the screen in order to register a selection. A touch screen comes in two forms, photonic and electrical.
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