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The main storage is divided into a number of storage locations that can be accessed by a unique number
or address, known as memory address. Within the CPU, there are high speed, special purpose memory
units called registers.
The control unit and the internal storage are linked together by the sets of parallel electrical conducting
lines called Buses. The buses that carry data are called ‘Data Buses’. To retrieve data from the memory, it
is necessary to identify the address of data in the main memory. The address is identified by (the memory)
‘Address Buses’. The buses that carry control signals are called ‘Control Buses’.
Output Devices
Output is the information obtained after the processing of data. The user receives the result through
output devices. Output can be in the form of soft copy or hard copy. Soft copy refers to the digital copy
which lies in the storage device whereas hard copy refers to the printed contents on a paper or film. Some
common output devices are:
Printer Plotter
l l
Monitor l Speaker
l
Printer
Printer is a common output device which is used for the purpose of printing documents. Printer generates
a hard copy of data or information.
Printers are of different types depending upon:
l Quality of Printing: The quality of output produced by the printer can be measured in units of dpi
(dots per inch) which is also termed as resolution.
l Speed: The speed of different types of printer varies widely. The speed of a printer is measured in
cps (characters per second), ppm (pages per minute) or lpm (line per minute).
l Printing Mechanism: There are different types of mechanism that are applied in different types
of printers. Some printers print by striking the printer head on the paper, some print by forming
images on the paper, some print by spraying of ink, etc.
Based on the mechanism, printer can be broadly classified into two categories:
Impact Printer l Non-Impact Printer
l
PRINTER
IMPACT NON-IMPACT
Line Printer Character Printer Ink-Jet Printer Laser Printer
Basics of Information Technology 19

