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Secondary Memory

            This memory is permanent in nature and is not directly accessed by the CPU. It allows users
            to store data that may be easily retrieved. It is cheaper compared to primary memory.

            Secondary memory devices are also called secondary storage devices. They are categorised
            into three types:
                                             Secondary Storage Devices





                    Magnetic Disk                    Optical Disc                    Flash Drive




                       Hard Disk           CD     DVD       Blu-Ray Disc      Pen Drive     Memory Card


            Magnetic Disk

            A circular metallic disk covered with a magnetic coating, that is used for storing data, is
            callled a Magnetic disk. You can record and erase data on a magnetic disk any number of
            times.

            Hard Disk

            The hard disk consists of one or more magnetic disks called platters.
            Each  disk  in  the  pack  has  top  and  bottom  surfaces  on  which  data
            is  recorded  using  a  magnetic  head.  It  is  permanently  fixed  in  the
            computer system. It is usually used for permanent mass storage. The
            most important function of the hard disk is to store program files

            and data files.
            The hard disk comes in a variety of sizes with storage capacities as
            high as 5 TB (TeraByte) or even more. The CPU accesses data stored
            on a hard disk much faster than it can access data on a CD.

            External hard disks are also available. They are the hard disks that
            can be connected to any computer with the help of a USB port.





                     The  first  hard  disk  was  introduced  by  Seagate  in  1979,  which  could  hold
                     5 MB of data.



            Optical Disc

            An optical disc is an electronic data storage medium that can be written to and read using
            a low-powered laser beam. The lifespan of an optical disc is longer than a magnetic disk.


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