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    Arithmetic Logic Unit: The Arithmetic Logic Unit or ALU performs arithmetic, comparison and
                        logical operations.
                         Control Unit: The Control Unit or CU controls all the functions of a computer. It also checks the
                        result given by ALU.

                         Memory Unit: The Memory Unit or MU holds the data that needs to be processed as well as the
                        data that has been processed by the CPU.

                      OUTPUT DEVICES

                      We have already learnt about some basic output devices like monitors, printers, etc. Let us now
                      learn more about these devices.

                      Printer

                      Printer is an output device that gives the output on paper. The result printed on paper is called
                      a hardcopy or printout. Printers can be classified into two categories: impact and non-impact.
                      Printers that have direct contact between the print head and paper are known as impact printers.
                      The printers that do not have direct contact between the print head and paper are known as

                      non-impact printers.
                      Laser Printer

                      This is a non-impact printer that uses laser technology to print text or
                      images on paper. It is expensive and gives the best quality output. The
                      speed of the laser printer is measured in pages per minute (ppm).
                                                     Inkjet Printer
                                                     This is a non-impact  printer that  outputs  text  and images  by

                                                     spraying ink on the paper. The speed of this printer is measured in
                                                     lines per minute (lpm). These are comparatively cheaper than laser
                                                     printers and the quality of output is also a little lower.

                      Dot Matrix Printer
                      This printer is an impact printer that contains a movable print head with
                      pins that strike the ribbon, placing a dot on the paper. These printers are
                      very noisy, less expensive, and slow to work. The speed of these printers is

                      measured in characters per second (cps).

                                               Plotter
                                               Plotter  is  used  for printing  vector  graphics,  visual charts, tables  and
                                               diagrams. Different types of plotters are:

                                                  Inkjet Plotter: It sprays small droplets of ink onto a piece of paper,
                                                   thereby creating an image.
                                                  Flatbed Plotter: The pen or the inkjet moves in horizontal and vertical
                                                   directions over a fixed horizontal flat surface on which the paper is

                                                   mounted.

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