It is an output device that is used convert soft copy or what you see to screen to hard copy (paper). It output the information on the screen to a sheet of paper. Most of today`s printer are connected to the system unit by a USB and even other are wireless. Earlier computer though used a different interface to connect.

The printer receives the information to be printed from the computer then it stores it into its RAM. The information stored in the printer RAM can be printed even if it is disconnected from the computer for any reason. From RAM the information is converted into instructions which are then printed. The printer also contains the ink or toner it also allow feeding of paper to be used in printing.

Classification of printers

Printer can be classified into 3 main ways:

How they print data

How the paper interacts with the printing head


How the paper interacts with the printing mechanism

This is the basic category and it classifies all printers into 2:

Impact printer:

These printer uses physical force to print images into the paper. The paper makes contact with printing ribbon example dot matrix.


They don’t use physical force to printer image and no contact between the paper and printing ribbon e.g ink jet and laser

How they print characters

The other way printers are classified is how they print the character. They are 2 classes which are:

Line printers

They print a whole line of the document at a time. All characters of the given line are printed together. This means the RAM size has to be big enough to hold the whole line to be printed e.g. drum printer

Character printers

They print each character at a time. It requires less printer RAM because in need to sore only one character e.g. Daisy wheel.

Printing technology

The next classification is the technology that is used to print. They include:

a) Ink jet printers

They are non-impact printers which produce a print by spraying a jet of ink through a nozzle to create small dot which becomes the part of the print-out. The manufacturer can use either piezoelectric technology of thermal inkjet technology.

inkjet printers


High quality print out.

Less noise compared with dot-matrix.

Low cost compared with laser printer.

Faster than dot-matrix

Ink cartridges cost less compared to toners used in laser printers.


The ink cartridge will require frequent replacement with is costly.

Cost of print per page is high.

The print can be blurred if is come in contact with water. It fades away when it get contact with water.

Nozzles are prone to clogging and damage.

b) Dot matrix printers

They are the oldest types of printer and they are impact printers. They use the concept of typewriter where the ribbon makes the print by direct impact with the paper being printed on.

dotmatrix printer


They are cheap (although they are not common these days)

The cost of printing is low.

They can print carbon copy

They can tolerate environmental changes like temperature.

Can be used with continues paper.


They create a lot of noise due to the printing mechanism that they use.

Have low printing speed

Produce black and white print only.

The quality of the print-out is low compared with other technology.

c) Laser printers

They are non-impact printers which uses toner. The toner is in a toner cartridge which can be either colored or black. It is fused on the paper with pressure from the drum and heat.

laser printer


It has the best print out compared to all the others printer.

Prints at a very high speed.

It prints quietly.

Offers high quality print because of it high resolution.

They are the most reliable printer around.

The print out is not affected by water.


The initial cost of acquiring is high.

Cost of toner is more expensive compared with ink used on other printers.

It is bulky.

Factors to consider when selecting a printer

  • Speed

Check the number of pages that a printer can print per minute. If you work involve printing bulk work then you may consider one that can print more pages. Another speed you need to consider is the time that the printer takes after you have sent the command and actual printing. Some printer takes more time than other.

  • Paper tray size

How many printing paper can the printer tray hold without need of refilling it. Also how many can it hold in the output side before they start falling from the holding bay. This depends on the purpose of the printer.

  • Cost

The first cost to consider is the initial cost when you are acquiring the printer the first time. This depends on your budget. The other cost is printer maintaining cost. This involves the cost of ink to be used, new toner and if the printer will need any special paper or only the regular.

  • Quality of print

It is measure in number of dots per inch (dpi). This is the number of dots that can be printed per inch of the printing material. The high the number of dots the better the print.

  • Interface to PC

This involves how the printer connects to the PC where it is getting the document. The latest printers use the USB connection and even others use wireless technology.


It is not categorized as a printer but it does the same job. Plotters are used to give the output but they draw line instead of the dot that the printer created when developing the print. Plotters are use mostly to created blue print and to print on big surface like the billboard advertisements.