what is input device

what is input device

Input devices get input from the external world to the computer. The input devices, which get input from the motion of the user’s hand, are known as handy input devices. Keyboard, light pen, digitizer, mouse, joystick and trackball, touch screen etc. are handy input devices.

Keyboard

The most common of all input devices is the keyboard. Several versions of keyboards are available. The best and most expensive of these is the full-stroke keyboard. This is ideal for word processing and other volume data and program entry activities. Some popular microcomputers offer enhanced keyboard for easy entry of numbers. This is accomplished with a smaller group of keys known as numeric keypad at the right of the keyboard. These keys generally consist of the digits, a decimal point, a negative sign, and an ENTER key. This type of keyboard is ideal for accounting operations, which require a large volume of numbers to be entered.

Keyboards generally utilize integrated circuits to perform essential functions, such as determining the combination of l s and Os, or binary code. To send to thc CPU, corresponding to each key depressed, switching between shifted and non shifted keys, repeating a key code if a key is held down for a prolonged period of time, and temporarily storing or "buffering" input when keys are typed too fast.

The keyboard arrangement provided as standard on most keyboards is the QWERTY arrangement. This arrangement was chosen to slow expert typists, since those who typed too fast would cause the keys on a mechanical typewriter to jam. Slowing down the typist was accomplished by scattering the most used around the keyboard, making frequently used combinations of letters awkward and slower to type. This QWERTY keyboard arrangement has been used for nearly a century.

Pointing Systems

Computer users frequently find it easier to point to something on a screen or at an item of text or graphical material they are entering into the computer, A number of devices are available to assist in fulfilling this need.

Mouse

A mouse is a hand-movable device that controls the position of the, cursor on a screen. It has a box with buttons on the top and a ball on the bottom. The box is placed on a flat surface, with the user's hand over it. The ball's movement on the surface causes the cursor to move.

Light Pen

The earliest pointing device is the light pen. This device is placed close to a screen or monitor and turned on. A photo sensor inside the light pen detects the scanning beam sweeping back and forth across the screen. Accompanying circuitry converts the pen's reading into the position of the pen on the screen. Light pens are used to select items from a list or menu displayed on the screen. Light pens are used to select items from a list or menu displayed on the screen and to draw graphic displays on the video screen.

Digitizer Pad

A digitized pad looks like a graph pad with a pointer. It functions like a light pen on a display screen except that the pad is mounted horizontally. As the pointer is moved on the pad, the corresponding point on the screen is illuminated. The digitized pad is useful in converting graphic input, such as charts, graphs, and blueprints into patterns that can be manipulated and stored by the computer.

Touch Screen

Touch screen detects the touch of a human finger. One popular technique used to detect the touch of a finger utilizes infrared light beams. In this touch screen technique, infrared light beams shine horizontally and vertically on the face of the screen. A pointing finger interrupts both horizontal and vertical beams, pointing its exact location.

Optical Input Devices

Optical input devices covert any image to digital form. The object or an image of the object is placed in front of the optical input device. The device then scans the object or its image, convert the scanned image into pixels. Scanner, digital camera etc. are optical input devices. They convert an image to bit-mapped graphics and deliver the graphics image to the computer. This image is hen store in the computer in different picture file formats (with BMP, TIF, and JPG etc. extensions). Optical character recognizer is a software package. It recognizes characters from a scanned image that exists in a picture file format.

Scanner

A scanner scans an image, converts it in bitmapped graphics and delivers to the computer. It is just like the photocopier machine, whereas the photocopier machine delivers the scanned output on paper, and the scanner delivers the scanned output as a packet of digital data, to the computer. The scanners have a row of light-sensitive diodes. These diodes can convert light with different color and intensity to different voltage. This is moved on the paper from its top to bottom. For each position of the row, a line of pixel is produced from the color and intensity of the reflected light from the paper. These pixels are delivered to the computer.

Digital Camera

Digital camera gets the image of a still or moving object, converts it to pixels and delivers to the computer. Still and movie both types of digital camera exist. Digital still camera has a light sensitive plate. When light from the object falls upon the plate, the plate supplies different voltage for different color and intensity of the fallen light from different points of the object. From these voltages, a digital image is produced and delivered to the computer. Digital movie camera takes many shots (more than 25 per second) of a moving object, then converts each shot to a digital image and delivers to the computer.

Optical Mark Reader

Optical mark readers (OMR) optically read marks on carefully printed forms. Optical mark forms are relatively expensive, as they must be printed with exact tolerances so that the marks will up under the optical sensing devices when read. The most popular use of such devices is optical character readers for scoring examinations in educational institutions.

Optical Character Recognizer

Optical character recognition (OCR) devices can convert data from source documents to a machine-recognizable form. OCR Current applications of optical scanning include billing, insurance premium notices, and charge sales invoices. At present, on OCR device can reliably read and interpret script or handwriting. However, some can read handwriting provided that certain general guidelines are observed when the data are written. Generally, optical character readers are limited with respect to hand-written characters and can only read handwritten digits and some symbols. Many OCR devices are available for the reading of typed characters, including digits, letters and some special characters. Not all printed characters can be read reliably on OCR readers. Generally, each reader is capable of reading only selected character styles.

Even if the character style and spacing are acceptable, errors can result from reading a character that is not written perfectly. To reduce such errors, OCR devices generally compare the pattern read with the patterns to all acceptable character. The read character is assumed to be the character whose stored pattern most closely matches the read pattern.

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