Key board is the most common and familiar input device. All programs and data are entering into computer through key board. Key board is similar to key board of type writer. When a key is press and electronic signal is produced which is detected by an electronic circuit called key board encoder. The key boards such as multimedia key board, web enabled key board, wireless key board etc. are available in present market.
The key boards contents all letters, digits, special symbol and character plus other keys which include
Functions keys whose operation can be determine by the user or program by the software being used.
Special keys such as those used to control movement of the cursor on the computer screen.
Mouse is a pointing device usually cursor contents two or three button as user rolls it on a flat surface, the mouse control cursor movement on the screen. Its movement and the direction of the movement are detected by the rotating wheels on the under side of mouse. Each wheels connected to a shaft encoder, which emits electrical palsies for every incremented movement of the wheel. The pulses transmitted by the mouse determine the distance moved.
When the user press one of the buttons, the mouse either names a place on the screen or makes selections from data on the screen. It can be used as an alternative too key board or it can be used in combination with a key board two enhance input operation. When the user moves the mouse across a flat surface the cursor on the CRT screen also moves in the direction of the mouse movement. The mouse can be used for many application, such as playing game, designing product with graphics, draw diagrams, maps etc.
OCR (Optical Character Reader)
OCR detects alphanumeric characters printed or type written in paper. It may be hand held scanner or a page scanner to detect light reflected from a line for from a page of the text. The change in the reflected line is converted to binary data, which is send to the processor. The text which is to be send illuminated by a low frequency light source. The dark areas absorb the light while the light is deflected from the lighted area OCR is used in large volume applications such as computer oriented bill printed by public utilities.
OMR (Optical Mark Reader)
Special marks such as square or bubbles are preparing on examination answer sheets for questionnaires. The users fill in these squares for bubbles with soft pencil or ink to indicate their choice OMR detects these marks and the corresponding signals are sending to the processor. If a mark is present it reduces the amount of reflected light is not reduced. This change in the amount of reflected light is used to detect the present of a mark.
MICR (Magnetic Ink Character Reader)
MICR is widely use by banks to process large volumes of checks and deposit forms written every day. Special ink called magnetic ink is used to write characters on checks and deposit forms, which are to be processed by MICR. It is capable of reading characters on a paper written with magnetic ink to identify the character when a check is entered in to a MICR it passes through a magnetic field. The read head reads the characters written on the checks with the magnetic ink. It interprets the characters and sends to corresponding data directly to the computer for processing.
OBR (Optical bar-code reader)
This method uses a number of bars of varying thickness and special between them to indicate the desire information. Bar code is used on most grocery item. OBR can read such bars and convert than into electrical palsies to be processed by a computer. The most commonly use bar code is universal product code (UPC). The UPC code uses a series of verticals bars of varying width these bars are detected as 10 digits. The first five digits identify the supplier or manufacturer of item. The second five digits identify individual product. The code also contents a check digit to ensure that the information read as correct or not.
A light pen is pointing device, it is used to select a display menu option on the CRT. It is a photo sensitive pen device. It is capable of sensing a position on CRT screen when its tip touches screen. When its tip is moved over the screen surface. Its photo cell sensing element detects the light coming from the screen and the corresponding signals are sent to the processor. The menu is a set of program choice offered to the user. A light pen also used for graphical work, such as pad packages computer aided design.
A touch screen is an electronic visual display that can detect the presence and location of a touch within the display area. The term generally refers to touching the display of the device with a finger or hand. Touch screens can also sense other passive objects, such as a stylus. Touch screens are common in devices such as game consoles, all-in-one computers, tablet computers, and smart phones.
The touch screen has two main attributes. First, it enables one to interact directly with what is displayed, rather than indirectly with a pointer controlled by a mouse or touchpad. Secondly, it lets one do so without requiring any intermediate device that would need to be held in the hand (other than a stylus, which is optional for most modern touch screens). Such displays can be attached to computers, or to networks as terminals. They also play a prominent role in the design of digital appliances such as the personal digital assistant (PDA), satellite navigation devices, mobile phones, and video games.