Computer Readable Devices and input or Output Devices most

Today We learn about Computer Readable Devices and input or Output Devices which most usually today this time many much more

Optical Mark Reader (OMR)

Optical Mark Readers (OMR) are special scanners used for recognizing a pre-specified type of mark made by pencil of pen For example, in the objective test paper of DOEACC NIELIT  (Department of Electronics Accreditation for Computer Courses), you mark your answers on a special sheet by darkening a small square, using a pen or pencil, The use of OMR is not Limited to the grading of Objective type tests In fact, any input data that nature of a choice or selection can be recorded for OMR input.
OMR focuses light on the page being examined and the light pattern reflected from the dark marks is then detected, Figure

Bar Code Reader

Bar code readers are special devices used to read bar coded data Bar code is a specialized code used for fast identification of items It consists of acess of small Lines known as bars These are primarily used for identification of goods, such as books, postal packages, badges, etc
Magnetic ink Character
Recognition (MICR)
MICR detects the special encoded characters on bank cheque sand deposit slips After detecting the encoded characters, the MICR converts them into digital data for the computer Figure shows a bank cheque which will be processed using a MICR device.

Optical Character Reader (OCR)

This device is capable of detecting alphabetic and numeric characters on a computer print-out containing complete pages of typed of hand written text. are scanned, they are compared with the characters that the machine has been programmed to recognize If the pattern of both characters matches, the scanned character is accepted for further operations.
It also reduces workload for people who have to feed large amounts of data into computers on a regular basis.
Card Reader
A card reader a device that reads punched cards. The punched card code code is detected b patterns of light passing through the holes in the cards.

Computer Input Devices Very Important

Video Cameras

A video camera takes continuous pictures and generates a digital or analog signal for display on a monitor or for permanent recording. Signals generated by video cameras are available the latter converts analog signals into digital form. Many and blue light across the line are filtered out to convert into a continuously variable analog these are then used for sending a picture over a network through computers.


Output devices supplies information or results either in the form of hardcopy printer or softcopy monitor some common out put devices include
1 monitor
2 Printers
3 Plotters
4 Multimedia projector
5 Speech synthesizer


Monitors come in two types
CRT (Cathode Ray Tube
TFT LCD thin much more than film transistor with liquid crystals in display

CRT Monitor

A VDU visual display unit or crt monitor is similar to a television and its size is measured in diagonal length of the screen monitors are available in 12 14 17 19 and even in 21 size it shows text or picture in colour or black and white depending on the type colour monitors are costlier than black and white monitors whatever you type on the keyboard you can see it on the monitor figure 2
19 shows a typical CRT monitor.

TFT-LCD Monitor

LCD monitor is the flat panel type of monitor found on notebook PCs TFT LCD is one type of active matrix LCD it is used in televisions flat panel displays projectors etc figure 2.20 shows a TFT LCD monitor TFT LCD has a sandwich like structure with liquid crystal filled between two glas plates TFT glass has as many number of pixels displayed while colour filter class has colour filter which generates colour liquid crystals move according to the difference in voltage between the colour filter glas and the TFT glass the amount of light supplied by back light is deter mined by the amount of movment of the liquid crystals in such a way as to generate colour.

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Printers are the most popular output devices they provide information in a permanent readable form they produce printed outputs of results programs and data a character prints one character of the text at a time they are low speed printers with their speed ranging from 300-600 characters per second character printers can be chassified as

1 Impact printers
2 Non impact character printers

Impact printers use an electro mechanical mechanism that causes hammers or pins to strike against able dot matrix printers and letter quality printers non impact printers do not use any electro mechanical printing head to strike against ribbon and paper they use thermal chem. Ical electrostatic laser beam or inkjet technology for printing the text usually a non impact type printer is faster than an impact type the disdvatge of non impact type printers in the they produce multiple copies of the text

Dot Matrix impact type character printers

A character is printed with the selected number of dots from matrix of dots Figure 2.21 shows a dot matrix printer the print head contains a vertical array of 7,9,14,18,or the column of dot matrix are printed b the print head at a time as it moves across a line see figure 2.22
Dot matrix printers are very flexible they do not have fixed character fonts the term font is used to refer to a character set of a printer as fonts are not fixed a dot matrix printer can print any shape of a character by software this permits printing of many.

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