A computer is a fast and accurate device, which can accept data, store data, process them and give a desired results as output. The computer is organized into four units as follows:-
Input Unit, Central Processing Unit (CPU), Output Unit and Secondary Memory.
Computers can process hundreds of thousands of computer words or characters per second. A high average speed for keyboard operation is two or three characters per second that’s when coded to form computer words, would reduce the data input rate to the computer to less than a computer word per second. The most commonly used input devices in this category are magnetic tape units, magnetic disk drive units, and floppy disk drive units.
Any device designed to assist in the entry of data into a computer is known as Input device. Input devices convert data from any convenient external format into binary codes that a computer can store and manipulate internally. Some of the most common, most popularly used devices are discussed underneath:
This Input device is categorized as pointing device because it is used to point and select an option on the monitor. It is connected to the computer by a cable and can be move around on the table. A pointer on the screen follows the movements of the mouse. In order to select an option on the computer screen, the user must move the pointer at the desired position and press the button on the mouse. The mouse can be used to open menus, select texts for editing, move objects on the screen, draw images or diagrams etc.
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A mouse can be classified on the basis of the number of buttons it has, the technology it uses, and the kind of interface it shares with the computer. A mouse may have one, two or three buttons. The program that uses the mouse determines the function of each button. A mouse may be classified as a Mechanical mouse and an Optical mouse, on the basis of the technology it uses.
A Mechanical mouse the rubber-coated ball that projects through the bottom surface rotates as the mouse is moved along a flat surface and sends electrical signals to the system unit by means of switches inside the mouse. This causes the cursor, or pointer, to move in a corresponding fashion.
An Optical mouse uses diodes to emit light beam instead of a rotating ball to detect movement across a specially patterned metal pad.
Keyboards are the most widely-used input devices. The most popular keyboards are those that look, feel and possibly sound like an ordinary typewriter keyboard. Alternatives are Membrane keyboards, whose keys are merely printed on a plastic membrane. A pressure sensitive two-dimensional keyboard covered with a dust-proofed and dirt-proofed plastic sheet are useful in dirty environments. Keyboards are of different varieties.
Generally, a keyboard has 105 keys. It features 12 function keys arranged at the top of the keyboard, and larger Backspace key, a numeric keypad, a cursor movement keypad, toggle lights, Shift keys, Alt keys, Ctrl keys, Caps Lock key, Num Lock key, Spacebar key, Enter key, Alphabetical keys etc.
This is categorized as a pointing device, which can be used only with video displays. It can be used to select an option by simply pointing at it, or drawing figures directly on the screen. An electron beam that repeatedly scans the display screen from left to right and from top to bottom produces a video display. The light pen, which is a pen-like device, has a photo detector at its tip. The detector can detect changes in the brightness of the screen.
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The light pen is connected to the computer by a cable. When the pen is pointed at a particular spot on the screen, the point is scanned and the photo detector records changes in the brightness and sends electrical pulses to the computer. The computer can find out the exact spot with this information. Light pens are useful for menu-based applications. It is also useful for drawing graphics in Computer Aided Design software.
Touch screens are normally used when information has to be accessed with minimum effort. The user need to only touch the appropriate point on the display to point out an item to the computer. This is again a kind of pointing device.
This is another kind of Input device used to play computer games, which is connected to game port.
This is the eye of your computer. It can see images or printed text and translate them into binary code. Most scanners collect data from a page by recording, which areas are light and which areas are dark. It contain a camera, which is made up of thousands of tiny cells, called Charge Coupled Devices (CCD). It transmits this data to the CPU, which then creates the image. Some scanners are sensitive enough to tell the difference between colours.
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