Input Devices

INTRODUCTION

The devices that are used to receive the data and instructions are called input devices. These devices are used to input program and data to the computer. These are the parts through which instructions or data are given to a computer for processing purpose. These input devices converts input data and instructions into a suitable binary form which can be accepted by the computer. Input devices are necessary to enter data and instructions into a computer as input unit is the only medium through which users can interact with the computer.

COMMONLY USED INPUT DEVICES

• Keyboard

A keyboard is the primary input device through which instructions and data are entered into the computer. It was first invented, in 1868 A.D, in America by Christopher Latham Sholes. This commonly used input device mostly uses a Qwerty layout. The layout is called "Qwerty layout" because such keyboard has those keys as the first 6 letters on top of an alphabetic line of a keyboard.

A keyboard is connected to the CPU with a cable. When a key is pressed, an electronic signal is produced which is then detected by an electronic circuit called keyboard encoder. The main function of an encoder is to detect which key has been pressed and to send a binary code that is correspondent to the pressed key of a computer. This binary code may be ASCII, EBDIC or HEX code.

Earlier, keyboard with serial port containing 9 pins was in use. These days, we have USB (Universal Serial Bus) port keyboard and some even wireless. Keyboard with navigation keys like play, pause, next, previous, etc. with multimedia functions is also available. There are 4 types of keyboards for PCs now available. The first 3 were invented by IBM while, the latter is the result of changes made when Microsoft Windows 95 was released. They are:

1. The 83-key keyboard (PC/XT)
2. The 84-key keyboard (PC/AT)
3. The 102-key keyboard (called the extended keyboard)
4. The 105-key Microsoft Windows 95-compatible keyboard)
   
   

• Mouse

A mouse is a small input device which is used to point, draw and select items that are displayed on the computer screen. The pointer of the mouse is called a cursor. As we move the mouse across the screen, the cursor moves according to the movement of the mouse. It was invented in 1960 A.D by Douglas Englebart.

A mouse is one of the most important and popular input devices. Its movement and the direction of movement are detected by 2 rotating wheels on the underside of the mouse. These wheels have their axes at right angles where, in each wheel is connected to a shaft encoder which emits electrical pulses for everyday increment movement of the wheel. The pulses transmitted by the mouse determine the distance moved.

There are 3 types of mouse found in a market.They are:

a.) Scroll mouse: It is a type of mouse which comes with a scroll wheel perpendicular to its surface. This scroll wheel or a mouse wheel is made up of a rubbery disc or hard plastic on the computer mouse. It is generally located between the right and left mouse buttons.

Fig: Scroll Mouse

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b.) Optical mouse: It is a more advanced mouse which uses a light source, typically LED (Light Emitting Diode), a DSP (Digital processing) and an optical sensor instead of the regular mouse ball. It uses a light detector such as an image sensor or an array of photodiodes to detect any relative movement to a surface.

Fig: Optical Mouse

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c.) Laser mouse: It is an even more advanced mouse which uses laser to detect movements on a surface. It can track more than 2,000 DPI (Dots Per Inch) whereas, a typical optical mouse can track between 400 and 800 DPI only. This mouse emits light to the surface where it is put on. The emitted light is reflected back which tells the computer to control the pointer on the screen. Generally, laser mouse available nowadays is connected to the USB (Universal Serial Bus) port.

• Joystick

The joystick was invented, in 1944 A.D., in Germany but the video game joystick was invented in, 1967 A.D. A joystick is a stick which is mounted on a spherical ball which moves in a socket. It allows the user to navigate easily around the display on the screen. A user may move the stick on the device in different directions. This is particularly useful at homes for playing video games and for indicating positions in graphic systems.

• Touch Pad

A touch pad is a small touch-sensitive pad that is used as a pointing device in portable computers. It can be used in place of an external mouse. It uses pressure sensors to track the position of a device on its surface. Each position on the touch pad is translated to the specific location on the screen.A touchpad is operated by using your finger.

Fig:Touch Pad

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• Track Ball

A track ball is an upside down of a roller mouse. It was used to be a basic input device in laptops earlier. It is similar to the mouse but with a mouse, the ball is rolled by moving the entire unit over the surface whereas, with track ball, the ball itself is rolled with fingers.

Fig: Trackball

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• Scanner

The scanner is an input device that needs images or text and converts the data into digital signals. The image is scanned and converted into a format that the PC can interpret. It was invented by Rudolph Hell, in 1963 A.D, in Germany.

A scanner works by digitizing an image, dividing it into a grid of small dots called pixel and representing each dot with RGB value for that pixel value by binary bits. The resulting matrix of bits is called a bitmap, which can be stored in a file and can be displayed on a screen.

• Bar Code Reader

The Bar Code Reader is a device which is used to read a barcode field. Bar Code is a technology that uses white spaces and black bars to represent encoded information. This encoded information can be read with an optical device that converts the bars and spaces into an electrical signal which is then decoded into the original characters. The bar code was invented by Woodland.

Fig: Barcode reader

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The bar code reader is used in labeling consumer products and books. It is detected as ten digits. The first 5 digits identify the supplier or manufacturer of the item whereas, the second 5 digits identify an individual product. The code also contains a check digit to ensure that the information read is correct.

• Light Pen

A light pen is a pencil shaped device which is used to select screen positions by detecting the light coming from points on a screen. It was 1^st invented in 1952 A.D, in MIT (Massachusetts Institute of Technology). A light pen is sensitive to the short burst of light emitted from the phosphor coating at the instant the electron beam strikes on a particular point.

Fig: Light pen

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Though the light pens are still in use, they are not as popular as they used to be as they have several disadvantages comparing to other input devices.

• OCR (Optical Character Reader)

Optical Character Reader (OCR) is the device that helps in the recognition of printed or written text characters by a computer. OCR is used for reading text from paper and translating it into a form that the computer can manipulate. An OCR reader scans the document using the photoelectric device to convert it into electric signals. These patterns are then compared with the stored patterns of the characters which the reader can recognize. If a match is found, the character scanned is identified otherwise, it is rejected by the reader. This device is widely used in airlines, banks, postal offices (for reading postal code), etc.

Fig: Optical Character Reader

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• OMR (Optical Mark Reader)

Optical Mark Reader is widely used device for scoring answers for multiple choice questions. It can sense the presence of a pen or pencil mark. Special marks such as squares or bubbles are prepared on examination answer sheets or questionnaires .The user fills in these squares or bubbles with soft pencil or ink to indicate their choice. These marks are detected by the Optical Mark Reader and the corresponding signals are sent to the processor.

Fig: Optical Mark Reader

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• MICR (Magnetic Ink Character Reader)

Magnetic Ink Character Reader has been used to read documents that are written by a special ink made of a magnetic material called magnetic ink. MICR is capable of reading characters on a paper written with the magnetic ink which is magnetized during the input process. The MICR reads the magnetic pattern of the written characters. To identify the characters, these patterns are compared with a special pattern stored in the memory. It is mostly used in banks and postal services.

Fig: Magnetic Ink Character Reader

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• Touch Screen

Touch screen is a kind of screen which is sensitive to user’s touch. One can use a finger to point the command or menu displayed on the screen. Touch screen was invented in 2009 A.D, in Apple store. It is widely popular on laptops.

Fig: Touchscreen

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• Voice Input System

The input system which is used to give the instruction to the computer invoice, without using the keyboard i.e. without typing is called Voice Input System. In Voice Input System, the speech is converted into electrical signals employing a microphone. The signals are sent to a processor for processing. Then, the signal pattern is compared with the pattern already stored in the memory .A word is recognized only when a choice is found, and then, the computer gives a corresponding output.

Fig: Voice Input System

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A voice recognition system can be used in factories at places where both hands of workers are engaged in the job like if he is doing some handful of work and he wants to input some data into the computer. It can also be used to assist handicapped people or for identification purposes in banks, etc.

(Karn & Pudasaini, 2015)

Bibliography

Karn, M. K., & Pudasaini, D. (2015). Computer Science I. Anamnagar, Kathmandu: Buddha Publication.