basics of computers

1. Output Devices

2. Output Devices
• Devices on which we obtain information out
from the computer.
• Many O/P devices, some of them are as
follows-
• Printer
• Plotter
• Monitor
• Synthesizer

3. Printers
A printer, produces a hard copy of documents stored in electronic form, on
physical print media such as paper or transparencies.
Printers can be classified into following categories:
• Classification A (text printed at a time)
1. Line Printer
2. Page Printer
• Classification B (quality of print out )
1. Dot Matrix Printer
2. Inkjet Printer
3. Laser Printer
• Classification C (head contact)
1. Impact Printer
2. Non-impact Printer

4. Line Printer
• The Line Printer is a form of high speed impact printer in which one
line is printed at a time. Print speeds of 600 to 1200 lines-per-minute
approximately.
• The disadvantages of line printers are that they cannot print graphics,
the print quality is low, and they are very noisy.
• There are following types of Line Printers :-
1. Drum Printer
2. Chain Printer
3. Bar Printer
4. Comb Printer

5. Drum Printer
• An impact printer.
• Consists of a cylindrical drum.
• A fixed font character set is fixed on its surface.
• One complete set of characters is embossed for each and
every print position on the line.
• The wheels, joined to form a large drum, spin at high
speed and paper & an inked ribbon are moved to the print
position.
• As the desired character for each column passes the print
position, a hammer strikes the paper from the rear and
presses the paper against the ribbon and the drum,
causing the desired character to be recorded on the
continuous paper.

7. Chain Printer
• It contains a steel band on which the character sets are
embossed.
• 4 sets of 64 characters are embossed on the band.
• For printing a line, all the characters in the line are sent
from memory to printer buffer.
• As the band rotates at high speed, hammer is activated.
• Hammer’s movement and chain movement should be
synchronised.
• Chain of the printer can be changed to use different fonts
using the same printer.

9. Serial Printer
• A printer that uses a serial port for connection to the computer.
• A printer that prints one character at a time, such as a dot matrix
printer.
• Also known as character printer.
• These are slow printers.
There are many types of serial printers –
• Dot Matrix Printer:
• The most popular impact character printer.
• The print head consists of pins.
• Characters to be printed are sent one character at a time from
memory to printer.
• The character code is decoded by the printer electronics and
activates the appropriate pins in print head.
• The printer prints the characters as a pattern of dots.
• The pins are moved forward to form a character and they hit
the carbon ribbon in front of the paper to print the character.
• Print Quality is lesser.
• Less expensive.

10. Serial Printer
1. Inkjet Printer:
• Non-impact character printer.
• Print characters by spraying ink onto the paper.
• Special type of ink having iron content used.
• Drops of ink are electronically charged after leaving a nozzle.
• These drops are then guided to proper position on the paper by
electrically charged deflection plates.
• Produce higher quality O/P.
• Colour printing is also possible.
2. Laser Printer:
• Very high speed non-impact printer.
• Also known as Page Printer.
• An electronically controlled laser beam traces out the desired
character to be printed on a photoconductive drum.
• The drum attracts an ink toner on the exposed areas.
• This image is transferred to the paper which comes in the contact
with drum.
• Comparatively expensive.

11. Serial Printer

12. Plotters
An output device, used to produce hard copies of graphs and designs.
These are of two types –
• Drum Plotter:
• The paper on which the design has to be produced is placed over a
drum that rotates back and forth to produce vertical motion.
• Contains pen(s) clamped in holder(s) to produce horizontal motion.
• Drum and pens move simultaneously.
• Different coloured pens are used to produce multi-coloured designs.
4. Flatbed Plotter:
• A plotter where the paper is fixed on a flat surface and pens are
moved to draw the image.
• This plotter can use several different colour pens to draw with.
• Has a stationary horizontal plotting surface on which paper is fixed.
• Pen is mounted on a carriage which can move in either X or Y
directions.
• Pen can move up and down.
• Used to trace graphs.

13. Plotters

14. Monitor
• A monitor is a piece of electrical equipment which displays viewable
images generated by a computer without producing a permanent record.
• Similar to television screen.
• Monitor output is softcopy.
• Monochrome and Colour Monitors:
 VGA (Video Graphics Array)
 SVGA (Super Video Graphics Array/Adaptor)
 EGA (Enhanced Graphics Adapter)
 CGA (Colour Graphics Adapter)
• Image consists of small dots known as pixels.
• More pixels give clearer image i.e. better display.
• Types of monitors used in PCs and laptops:
 Cathode Ray Tube (CRT)
 Flat Panel Display:
 Liquid Crystal Display (LCD)
 Electro Luminescent (EL)
 Gas Plasma (GP)
 TFT (Thin-film Transistor)

15. Monitor

16. Audio Output
• Audio output is the second type of softcopy.
• In order to have high quality, sound card as well as good speakers are
required.
• Computer speakers or multimedia speakers are equipped with a
low-power internal amplifier .
• Computer speakers range widely in quality and in price.
• Generally speakers with computer systems, are small plastic boxes with
dull sound quality.
• Internal speakers are also available in the computer market.
• Some of the slightly better computer speakers have equalization
features such as bass controls, improving their sound quality
somewhat.

17. Audio Output