1. INTRODUCTION TO COMPUTER
CHAPTER N0 2
INPUT & OUTPUT DEVICES
ADEEL ANJUM

2. OUTPUT DEVICES
An output device is used by computer to communicate its results or message to the outer world.
A device which transfers the data or program from computer memory to outer medium. For example the monitor or printer.
Almost every computer will include a device that outputs data in human readable form.
Example:monitor,printer,plotter,speakers etc.

3. What are two categories of output data?
Soft copy and hard copy are two categories of output data.
SOFT COPY
it is data that is shown on display screen or is in audio or video form
it exist only electronically. it cannot be touched. its like music.
HARD COPY
it is printed output. for example print out.
MONITOR
it is an output device that shows result in soft form on screen.
There are two types of monitor CRT and FLAT PANEL.
CRT (cathode ray tube)
In 1897 German physicist invented CRT. Cathode ray tube is very popular output device as far as the communication with the computer is concerned. The monitor is similar to a television screen and in fact for some computers the television screen can be used as the monitor. screen is usually divided into 25 rows each of which have 80 characters.

4. FLAT PANEL
It is made up of two plates pf glass separated by a layer of a substance in which light is manipulated. It use liquid crystal display (LCD) technology.
It is much thinner ,weight less,portable,consume less power as compares to CRT.

5. PRINTER
Printer is output device used to prepare permanent document on a paper for human use.
A computer peripheral that puts text or a computer generated image on paper or on another medium.
Printer can be categorized in several ways the most common distinction
1.IMPACT
2.NON-IMPACT.

6. LINE PRINTERS IMPACT PRINTER
It use such method which is used by the typewriters? In some type of impact printing a metal "hammer" with a character strikes on print ribbon, which presses the characters image into paper.
TYPES OF IMPACT PRINTER.
LINE PRINTER
DOT MATRIX PRINTER
DAISY WHEEL PRINTER
LINE PRINTERS
it is type of impact printer that prints one line at one time, as opposed to one character at a time. They are high-speed devices and are often used with mainframes, minicomputers, or networked machines rather than with single user system. Types of line printers include chain printers and band printer.

7. TYPES OF NON IMPACT PRINTERS LASER PRINTER INK JET PRINTER
DOT MATRIX PRINTER
It contain a print head of small pins that strike an inked ribbon against paper to form image .it produce lot of noise because of the print head striking the paper.
DAISY WHEEL PRINTER
The D.W.P is a flat circular device made of metal with character embossed on it. As this wheel spins at a very high speed the hammer hits the specific character against the ribbon which presses against the paper.
NON – IMPACT PRINTING
it create character and images without direct physical contact between the printing mechanism and paper.
TYPES OF NON IMPACT PRINTERS
LASER PRINTER
INK JET PRINTER
THERMAL PRINTER
PLOTTER 7

8. INK – JET PRINTER PLOTTER LASER PRINTERS THERMAL TRANSFER PRINTER
An electro photographic printer that is based on the technology used by photocopiers. Laser printer run with a software called page description language (PDL).It has its own CPU,ROM,RAM.it can produce 4 to 12 pages per minute (ppm).
THERMAL TRANSFER PRINTER
It is a kind of non-impact printer. In electro-thermal printing, characters are burned on to a special paper by heated rods on a print heat. They transfer ink from a ribbon onto plain paper. These printers can support high quality graphic.
INK – JET PRINTER
It is a kind of non-impact. spray small dots of electrically charged ink onto a paper to form images.
PLOTTER
The plotter is an output device. It is an example of non impact printer. plotters are designed to produce large drawing or images such as construction plan for buildings.