Memory Hierarcy

1 Dec

Various memory devices are used in a computer system.
They have different speed and costs.
A memory system of a computer is a hierarcy of storage devices with different capacities, cost and access speed.


Non Impact Printers

1 Dec

a)Inject Printers : Inject printers works by spraying into a paper.
Magnatize placed in the ink part, direct the ink on to the paper in the
desired shape. A typical engine printer provides a resolution of 300 dots per inch(These are 300 inchs).b)Laser Printers : Laser printers uses beam of light to produce an image on a drum. The light of a laser alters electrical
charge on the drum wherever it hits. The drim is then rolled through a reservoir toner. Which is picked up by the charge
portions of drum.

Finally the toner is transferred to the paper through a combination of heat and pressure.

Impact Printers

1 Dec
This refers to the cass of printers that work by banging a head againts and ink ribbon to make
mark on the paper. This type of printers include dor matrix printers, daisy-wheel printers and line printers.
Impact printers are considerably noisier than nonimpact printers. These are used in applications like word processing and report writing.
There are 2 types of non impact printers(Dot Metrix Paper, Daisy Weel Printers).

a)Dot Metrix Paper : A type of printer that produces character by sitriking pins against an ink ribbon
tp print closely spaced dot in approprate shape. Dot metrix produces low quality prints and outputs
Because of which it is not suggested to print images.

b)Daisy Weel Printers : It works on the same printible bool head type writer.
The daisy wheel is made of metal on which characters stand how. to print a character,
the printer rotates the wheel intil letter is facing the paper. Then hammer strikes the wheel forcing the character
to hit an ink ribbon, leaving an impression of the character on the paper.

What is a Printer?

1 Dec

Printers are output devices which are used to generate the hard copies of documents.
Printers are 2 types(Imptact Printers, Non Impact printers).

What is Optical Character Recognition(OCR)?

1 Dec

Refers to the branch of the computer that involves reading text from paper and transliating the text
into a form that the computer can manupulate OCR systems enable us to take a book or magazine and feed it directly into computer file.

What is Optical Barcode Reader?

1 Dec

-Uses a number of bars of varying thickness and spacing between then to indicate the desired informations.
-Bar codes are used on most grocery items.
-An optical bar code reader can read such bars and convert them to electrical pulses to be processed by the computer.

What is Optical Mark Reader?

1 Dec
-Various examination answering is done by filling square or bubble with soft pencil.
-Optical mark reader detects these marks ad sends corresponding signals to the processor.
-If a mark is present it reduces the amount of light reflected.
-If a mark is not present, the amount of light reflected is not reduced.
-This method is used where one out of few number of alternatives is to be selected and marked.