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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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