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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 device, such as a a hard disk is covered with a magnetic coating. 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 magnetic head.
                 It is permanently fixed in the system unit. It is usually used
                 for permanent mass storage. The most important function
                 of the hard disk is to store program files and data files.                         Hard disk
                 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 USB port.
                                                                                               External hard disk
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                   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.


                 Compact Disc (CD)
                 The CD drive reads information stored  on a compact disc
                 (CD). CD is an external storage device. The lifespan of optical
                                                                                                     CD-Drive


                                                                                  Fundamentals of a Computer         15
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