Input device of computer system

Input is the acceptance of data by the computer. It is done by means of an input device.

Input Devices

There are two types of input method: indirect and direct  methods.

 Indirect methods 

Indirect methods of data input involve preparing data into a form that the computer can read before inputting. For example, punched cards and paper tapes are indirect input methods. They have to be punched and verified before feeding into the computer. Therefore, extra work is required and many errors can be introduced during the data preparation stage. Today, these indirect methods are used less often.

IBM80-column punched card format in early 1800s

 Direct methods 

The computer reads data directly from the source without any additional keying in. These methods are much quicker and transcription error is eliminated as there is no need to do any copying.

 Input Devices 

1. Keyboard

The most common method of inputting data into a computer is by typing on a keyboard. Not only the one you use at home , but also you can see the special keyboard in a McDonald's restaurant ! There are many designs of keyboards, some are with trackball so that users need not to move their hands away from the keyboard when accessing a pointing device. There are also wireless keyboards, making use of the infrared technology.

    2. Magnetic card reader

This device can read the magnetic stripes on the back of bank cards or common stored value tickets. The magnetic stripes are encoded with data appropriate for the application.

For example, your ATM card has the account number stored on it. The magnetic card reader is commonly used as an input device in the easy pay system (EPS).

3. Bar-code scanner

Hand-held scanner	Light-pen scanner	Desktop scanner

A bar  code is a set of parallel black and white lines of different thickness which represent a number. The number is also printed below the bars.

A bar-code scanner is the input device used in the point-of-sale (POS) terminal, for example, at a supermarket. Light pen, laser scanner, both are types of bar-code scanner. Both are sensitive to the amount of reflected light.

4. Optical mark reader (OMR)

This device can sense the presence of a pen or pencil mark. It is commonly used for processing large quantities of simple, repetitive data such as marking multiple-choice questions

	This kind surveys or test answer forms are usually process by OMR

5. Optical character reader (OCR)

This device can recognize characters that are printed in a specific type font. The optical character reader can distinguish one character from another by its shape. Handwriting can also be recognized if the characters are well formed.

It can optical character reader scans the document and converts the shape sensed into a pattern of electronic signals. The sensed pattern is compared with the stored patterns of the characters. If a match is found, the character sensed is identified. If a match is not found, that part of the document is rejected.

>> Advantages :

Data are held in a form that can be read by both humans and machine. The data are given directly to the computer. So it is a fast and accurate data entry method.

There is some OCR that allows blind people to read books. The optical scanner reads and converts them to Braille using a Braille display device.

6. Magnetic ink character recognition (MICR)

Characters are printed with an ink containing a substance that can be magnetized. The character shapes are recognized by the magnetic ink character reader. 

MICR is used mainly in banks. Each cheque is printed with the cheque number, the bank's identification number, and the customer's account number.

The advantage for bank to use this kind of input device is that the cheque can still be read even if the cheque is folded or overwritten with signature.

　

An example of an MICR character set

7. Joystick/game paddle

This input device allows the user to interact with the computer program, usually a game.

8. Mouse

The mouse is a mobile switch that controls the position of the cursor on the screen. A ball underneath the mouse electronically transmits the direction of movement. The cursor, under the control of the mouse, can be used to select one of several options displayed on the screen. The option is selected by pressing a button on the mouse.

A new type of mouse  ( using laser beam to replace the ball underneath )

9. Image scanner

This device allows direct entry of both pictorial information and text-based information. An image scanner uses laser technology to scan and digitize an image. It is the most common type of scanner for home-users.

The image has been scanned and digitized.

10. Light pen

A light pen is a pen-shaped device that is sensitive to the presence of reflective light, just like the light pens can be used to read bar codes. It uses optical technology to work closely with the monitor. It reads the light emitted from the monitor as input and converts it back into digital signals to be fed into the computer.

11. Speech recognition devices

Speech recognition devices convert spoken commands into sequence of electronic signals. When the computer hears a word, it then looks for a match and if it finds one, it displays a written version. The most successful devices are speaker-dependent. They are 'trained' to respond to the speech of a particular individual.

One very useful application of this technology is to aid handicapped people who have poor control of their body's movement. 

　12. Digital camera

Digital camera becomes increasing popular nowadays. The photo that is taken by the digital camera is digitalized and save in the memory card. The files are transferred to the computer and can be seen on the screen.

It is believed that the digital camera will replace the traditional camera in the coming future!

　13. Chinese hand writing recognition device

This kind of input device is usually with a writing pad for inputting the words. The program can recognize the handwriting and convert to words that are presented on the screen. It is widely used in inputting Chinese characters, instead of English characters as the low input speed.  A common brand of Chinese hand writing recognition device, 蒙恬筆

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