Input devices are those devices by which Data and instructions are entered into a computer. An input device converts input data and instructions into a proper binary form which is stored in the memory of a computer.
The most commonly input device is known as keyboard. Some input devices are known as pointing devices like mouse, light, pen, graphic tablet, joy stick, track ball, touch screen, etc. Each of these devices permits the user to select something on the monitor screen by pointing to it. So these devices are also called pointing devices. A microphone equivalent to the one used with a public address system is used for voice input.
Programs and data are entered into a computer by a keyboard which is attached to a computer. A keyboard is equivalent to the keyboard of a typewriter. It has letters, digits, special characters, function keys and some control keys. When a key is pressed then an electronic signal is created, which is detected by an electronic circuit called keyboard encoder.
There are 12 function key at the top of the keyboard which from F1 to F12. Their functions depend upon the program being run.
Special purpose keys
Backspace key: The backspace key erases a character instantaneously to the left of the cursor.
Enter key: The enter key is known as return key on a keyboard. It is used to show the end of a line or a paragraph. It is also used to show the end of the command given to a computer to allow it to execute the instruction.
Esc Key: The Escape key is used to initiate a personal computer to cancel the command just given.
Shift Key: When we press and hold the shift key and type lower case a, we gets an upper case A on the screen as in the case of a typewriter. Whenever the Caps Lock is on then above result is reversed. By pressing shift key we can write upper symbols such as @ # $ % & * etc.
Caps Lock Key: When we pressed Caps Lock first time then all letters will be typed in Upper case. If we press the Caps Lock key again, all letters will be typed in lower case. Press the Caps Lock key to type a letter in upper case.
Tab Key: By press Tab key, we can position the cursor at the predetermined position on screen.
Ins Key: Ins mean insert. The Ins key works both in insert and overstrike modes.
Delete Key: By Del key we can erase the character appearing just above the cursor. The function of the Del key is different from that of the backspace key.
Print screen: We can take print screen by pressing PrntScr key.
Mouse: A mouse is a pointing device which is detained in one hand and moved across a flat surface. The mouse is also used to draw sketches and diagrams on the monitor screen. It is also moved on the graphic tablet for drawing work. The mouse is also used to edit text. For editing a text on the screen, the cursor can be fast placed close to the preferred point of the screen by moving the mouse.
One type of mouse uses a rolling ball, others use optical sensing techniques. They are linked to the PC with a cable or by using infrared light. A classic mouse has two or three buttons.
The mouse buttons do depend on the application program running in our PC. In a few systems, it is also possible to identify independent functions to the buttons.
Joystick: A joystick is known as also a pointing device and used to shift the cursor position on a monitor screen. Its function is like to that of a mouse and it is used for playing games.
A joystick has a spherical ball at its lower end as well as at its upper end. The lower spherical ball shifts in socket. The joystick can be shift right or left forward or backward. The electronic circuitry within the joystick detects and actions the displacement of the joystick from its essential position.
A scanner is also known as a hardware device which is used to scan text and images into the computer. At times the information picture or text that is obtainable on paper is required on the computer. The essential function of a scanner is to convert a document into digital format. Scanners are mainly desktop analog to digital converter. They take analog illustration things, documents, magazine papers, photos, business cards etc.
There are different types of scanners
1. Flatbed scanner
2. Sheetfed scanner
3. Handheld scanner
Trackball: A trackball is also known as a pointing device which contains a ball which can rotate in any direction. The customer spins the ball in dissimilar directions to move the cursor on the monitor. The connected electronic circuitry detects the direction and speed of the spin and sends this information to the processor. This type of pointing device is generally used in a laptop.
Light Pen: A light pen is also known as a pointing device and it is used to select a displayed menu option on the monitor. Light pen is a photosensitive pen like device accomplished of sensing a position on the monitor screen when its tip touches the screen. When its tip is shifted over the screen surface, its photocell sensing element detects the light upcoming from the screen and the equivalent signals are sent to the processor. The menu is a set of programmed choices offered to the consumer. The consumer indicates his choice by touching the light pen beside a desired description of the menu.
Voice input and recognition System:
Voice input and recognition system is also an input device and consisting of a microphone that converts human speech into electrical signals. A signal pattern obtained in this manner is sent to the computer where it is matched against pre stored patterns to recognize the input.
Optical Mark Reader (OMR): It is special scanners used for identify a pre-specified type of the mark made by pencil pr pen. It is particularly used for examination the answer sheets of examinations having multiple choice questions. For example in the objective test paper of DOEACC, we mark our answers on a unique sheet by darkening a small square using a pen or pencil. These answer sheets are fed into the computer by using the optical mark reader. The computer can then calculate the answers sheets. The use of OMR is not limited to the grading of objective type sheets.
Bar code Reader: Bar Code Reader are particular devices used to read bar coded data. Bar code is a particular code used for fast identifications of items. It has a series of small lines which is known as bars. The real coding of the bars is depending on the width of the bar not to height. These are mainly used for recognition of goods such as books, postal package etc.
Magnetic Ink Character Recognition (MICR):
MICR detects the particular encoded characters on bank cheques and deposit slips. After detecting the encoded characters, the MICR converts them into digital data for the computer. The aim of MICR line in a check is to allow the check information to be automatically read by cheap machine. MICR has only 14 characters and one cannot print an entire check using this font. A particular purpose machine known as a reader/sorter reads characters made of ink containing magnetized particles.
Optical Character Reader (OCR) This device is accomplished of detecting alphabetic and numeric characters on a computer printout containing complete page of typed . The characters are examined by passing them under a strong light and lens system. The inked areas are differentiated from those which are not inked. Once the whole characters are scanned they are compared with the characters that the machine has been programmed to identify. If the pattern of both characters matches, the scanned character established for further operations.
· It makes data entry simple and faster using scanners.
· It is also reduces workload for people who have to supply large amounts of data into computers on a regular basis.
A card reader is also input device which reads punched cards. A punched card is a storage medium made of thick paper card that holds data in the form of punches holes. The holes are punched into the card by a key punch machine or card punch peripheral device attached to a computer.
The punched card code is detected by patterns of light passing through the holes in the cards.
Another card reader called captivating card reader is used for reading the magnetic strip on the back of credit cards and transferring data sent through the card.
A video camera takes continuous pictures and generates a digital or analog signal for display on a monitor or for stable recording. Signals generated by video cameras are accessible. The latter converts analog signals into digital form.
A video camera captures images by breaking down the images into a series of lines. Every line is scanned one at a time and the constantly varying intensities of red, green and blue light across the line are filtered out to convert into a continuously variable signal. These are then used for sending a picture over a association through computers.