• Devices on which we obtain information out
from the computer.
• Many O/P devices, some of them are as
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
• 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
• 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
• 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
• 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
• It contains a steel band on which the character sets are
• 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
• Chain of the printer can be changed to use different fonts
using the same 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
• 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.
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
• Comparatively expensive.
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
• Pen can move up and down.
• Used to trace graphs.
• 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)
• Audio output is the second type of softcopy.
• In order to have high quality, sound card as well as good speakers are
• 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