What is a Line Printer? How can it vary from a Dot Matrix printer?

A Line printer is a manifestation of rapid effect printer in which a line of sort is printed at once. Print velocities of 600 lines to 1200 lines/mt is normal. There are three fundamental sorts of line printers. They are:

1. Drum Printers

2. Chain Printers

3. Bar Printers

A Dot Matrix Printer utilizes a head which hold a lattice of pin heads. Contingent on the character to be printed, a set of pin heads from the network is somewhat anticipated outwards to structure the state of character to be printed. This head gathering moves from one end of sheet to flip side in a line printing one character at once. Head strikes a lace which is kept over the paper and make an impression of the anticipated pins.

What is Optical Mark Reader (OMR) ?

OMR is a special scanning device that can read carefully placed pencil marks on specially designed documents. OMR is frequently used in forms, questionnaires and answer sheets. Modern OMR can read black or blue marks made with ball point pen or fel tip pen as well as pencil, punched and printed marks. Normal scan area includes 12 rows at 0.25 inch centers * 126 mark positions and scanning speed 25 inches per second.

What is Magnetic Ink Character Reader (MICR) ?

MICR is a character recognition technology adopted mainly by the banking industry to facilitate processing of cheques. MICR uses predefined shapes for characters. MICR characters are printed with a magnetic ink or toner. Magnetic printing is used so that the characters can be reliabily read in a system even when they have been overprinted with other marks such as cancellation stamps. MICR reader is similar to audio tape recorder head. The letter forms ensure that each letter produces a unique waveform for the read head. MICR is used by the banks. As the head of MICR reader moves over the characters, according to the character, a unique waveform is generated.

What is data hiding in a program?

Data hiding is a key feature of object oriented programming. It means that data is concealed within a class so that it cannot be accessed mistakenly by functions outside the class. The primary mechanism for hiding data is to put it in a class and make it private. Private data or functions can only be accessed from within the class. Public data or functions are accessible from outside the class. Data hiding provide a mechanism to protect well intenioned programmers from making mistakes.
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