INPUT DEVICES

Input Devices

An input device is a hardware device that sends data into the computer system. These devices are used to input (or enter) data and instructions into the computer system. All instructions are accepted by the CPU through electrical pulses from various kinds of input devices.

Some of the input devices are explained as follows:

Keyboard

It is the most commonly used input device which uses an arrangement of buttons and keys.Both, data and program, can be entered into the computer through the keyboard. It is an essential device for interactive processing because the user can easily issue commands to receive the data response immediately on the computer screen.

Types of Keys on Keyboard

(i) Alphanumeric keys All of the letters and numbers on the keyboard are A-Z and 0-9.

(ii) Punctuation keys Such as comma, period, semicolon, brackets, parenthesis and so on.

(iii) Special keys Such as Control keys, Arrow keys, Caps lock key, Delete key, Alt key, Shift key etc.

(iv) Function keys Keys labeled F1 to F12.

These keys have different functions depending on the running program.

Pointing Devices

A pointing device is used to communicate with the computer by pointing to the locations on the monitor. It can also be used for:

  • sending command signals to the computer.
  • selecting items on the screen.
  • selecting commands from commands menu.
  • drawing graphics, sketches, etc.

Some commonly used pointing device are mouse, , joystick, lightpen, graphics tablet, touch screen, touch pad and trackball.

i) Mouse

The mouse is a pointing device that allows to control the movement of pointer (also known as mouse pointer) on screen. Mouse performs various functions by detecting two-dimensional motion relatively to its supporting surface. A mouse can be of different types like wired, wireless mouse, optical mouse, mechanical mouse etc. Generally a mouse have two buttons – a right button and left button.

Mouse also include a scroll wheel between the buttons to scroll down the application window.

Different types of mouse are:

(a) Mechanical Mouse In this type of mouse, movement of a cursor on the screen is relative to the movement of the ball available at the bottom of the mouse.

(b) Optical Mouse It uses a Light Emitting Diode(LED) and photodiodes to detect movement.

(c) Laser Mouse It uses Infrared Laser Diode instead of a normal LED.

(d) Wireless Mouse It communicates with the computer via Radio waves (often using Bluetooth hardware and software) so that a cord is not needed (but such mouse needs internal batteries).

A mouse also includes one or more buttons (and possibly a scroll wheel) to allow users to interact with the GUI(Graphic User Interface).

(ii) Joystick

The joystick is also a pointing device like the mouse, which consists of a stick that pivots on a spherical ball on its base. A joystick is similar to a mouse except that the movement of cursor on screen stops working as soon as user stop moving the mouse. But with a joystick, the pointer continuous moving in the previously pointing direction.

Commonly, joysticks are used for playing computer games like flight simulators but occasionally used for CAD/CAM systems and other applications.

Some joysticks also have a third degree of freedom i.e. the stick can be twisted in clockwise or anti-clockwise direction.

(iii) Light Pen

A light pen is a pointing device shaped like a pen and is connected to a Visual Display Unit (VDU).

The tip of the light pen contains a light- sensitive element which, when placed against the screen, detects the light from the screen enabling the computer to identify the location of the tip of pen on screen.

(iv) Graphics Tablet

A graphics tablet (or digitisers, digitising tablet, tough tablets or simply tablet) is an input device that consists of an electronic writing area and a special pen that works with it. It allows artists to create hand-made images and graphical images with motion and action, similar to the way a person draws images with pencil and paper.

The pen of the graphics tablet is pressure sensitive, so pressing harder or softer can result in brush strokes of different width.

When user draws anything on the tablet with the special pen, the drawing appears on the screen.

The tablet and pen can also be used like a mouse to move the cursor and click.

Graphics tablet may also be used to capture data or handwritten signatures.

(v) Touch Screen

It is an electronic visual display that can detect the presence and location of a touch within the display area. The term touch screen generally refers to touching the display of the device with a finger or hand. The touch screen sends a signal to the computer. This signal gives the location on the screen, which has been touched. Touch screen is quick and simple to use. Generally, smartphones have a high-resolution capacitive touch screen.

There are two basic types of touch screens available with electronic devices like capacitive touch screen and resistive touch screen. 

Touch screen is pressure sensitive and activated by finger or stylus. Touch screen works as:

Touch sensor It is a clear glass panel with a touch responsive surface.

Controller A small PC card that translates information that PC can understand.

Software Driver It allows to work with existing software.

(vi) Touchpad (Trackpad)

It is a specialized surface that can translate the motion and position of a user’s finger to a relative position on the screen. This is a common feature of laptop computers and also used as a substitute of a computer mouse, where disk space is scarce. The sensors of touchpad only react through fingertip and not a pencil or other object.

There are usually two buttons next to the touchpad which works as left and right button of the mouse.

(vii) Trackball

It is designed for computers, generally serves as mouse replacement. It is primarily used to move the cursor on the screen. The trackball has a ball on its top.

Trackball can be rolled with fingers and the internal rollers sense the motion, which is transmitted to the computer.

Trackballs are common on CAD workstations and sometimes seen on computerized special purpose work stations, such as the radar consoles in an air-traffic control room or sonar equipment on a ship or submarine.

Scanner

It is a device that allows a user to take an image or text and convert it into a digital file, allowing the computer to read or display the scanned object. Scanners can be used for storing the documents in their original form that can be modified and manipulated later on. It is mainly used to convert a scanned document in a digital format.

Scanners come in a variety of sizes from hand-held models to desktop models as discussed below:

(i) Hand-held Scanners They are so small that they can be held in hand. These are relatively cheap  and narrow. Hence, in order to scan a single page image, multiple passes are required. But their handiness is a major advantage of hand-held scanner.

(ii) Flatbed Scanners They are large and more expensive scanners that creates higher quality images. These scanners have a flat surface on which the printed image to be scanned, is placed. (Similar to the way a page is placed on a photocopier). Flatbed scanners can scan a page in a single pass.

(iii) Drum Scanners They are medium size scanners with a rolling drum. The sheet is fed through the scanners so that the drum rolls over the entire sheet to be scanned (Just as the sheets are fed in a fax machine).

MICR

(Magnetic Ink Character Recognition)

It is a character recognition technology which is primarily used by the banking industry to facilitate the processing of cheques. This technology allows the computers to read information (such as account numbers) on printed documents. Characters are printed in special typefaces with a magnetic ink (that contains Iron Oxide).

MICR can read upto 2400 documents/min. The MICR coding system contains 14 characters (four special symbols and 10 decimal digits). So, it can recognize these 14 characters only. The type font E-13 B, a standard typographical style, is used to print the characters or identification marks.

OCR (Optical Character Recognition)

It is used to translate scanned images of handwritten, type-written, printed text or special type font printed on conventional paper with conventional ink into machine- encoded text.

It is widely used to convert books and documents into electronic files, to computerize a record-keeping system in an office or to publish the text on a website.

An optical reader uses photoelectric devices to scan the characters being read and convert the reflected light patterns of the data into binary data suitable for computer input.

The normal speed of an OCR is 1500 to 3000 characters per second.

Technology is being developed for more accurate recognition and is known as Intelligent Character Recognition (ICR).

OMR (Optical Mark Reader)

It is used to capture human marked data from document form such as surveys and tests.

One of the most familiar application of optical mark reader is the checking of optical answer sheets in multiple choice type questions.

It uses high intensity light to read the marks or symbols by reading contrasting reflectivity.

Barcode Reader

It is an input device used for reading printed bar codes (Universal Product Code) available on product to be sold. A bar code reader emits a beam of light, which reflects off the bar code image.

A light sensitive detector in the barcode reader identifies the bar code image by recognizing special bars at both the ends of the image.

Once code is identified, it is converted into a numeric code. A perfect example of a barcode reader is its use in a super market where barcode scanner reads the price of a product.

Software like Wasp, BarCode Pro are used for scanning and printing barcodes.

A barcode is a machine readable representation of information in the form of stripes of varying thickness.

Microphone (Mic)

We can send sound to the computer through a special manual input device called microphone or mic. A mic converts the received sound into computer’s format, which is called Digitised Sound or Digital Audio. To convert a voice into digital form, an additional hardware is always needed which is known as Sound Card.

Sound is used most often in multimedia, where user can make his/her presentation more attractive using recorded narration, music or sound effects.

A microphone can be attached to a computer to record sound. Now-a-days, microphones are also being used with speech recognition software.

This means that you do not have to type the document, rather just have to read it out loud and the spoken words appear in your digital document on the computer.

Web Camera (Webcam)

Webcam is a digital camera attached to computers and can be used for video conferencing or online chatting, etc. It is a video capturing device. Webcams are able to capture full motion videos as well. A webcam connected to a computer allows the user to view either a picture or video of a user or other objects.

Now-a-days, webcams are either embedded into the display with laptops or connected via USB or firewire port or wi-fi to the computer system. After connecting webcam to a computer, you need to install required software or drivers.

Digital Camera (Digicam)

It is a device that stores the pictures or videos in an electronic format instead of a photographic film.

There are several features that make digital camera a popular choice, when compared to film cameras. Most enjoyable feature is the LCD display on the digital camera. This display allows users to view and save photos or video after the picture or video has been taken, that means, if you take a picture and don’t like the results, you can delete it, or if you like the picture, you can save it and easily show it to other people.

Biometric Sensor

It is a device which recognizes physical or behavioral traits of the individual. Biometric sensors are mainly used marking attendance of employees/ Sensor studentsin / organizations /institutions.

Biometric sensors are very accurate,  so these can be widely used for security purposes.

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