Page 45 - PlusGPT_V2.1_C7_Flipbook
P. 45

Read-only Memory (ROM)

                 Information stored in ROM is permanent in nature, i.e., it holds the data
                 even if the system is switched off. It holds the starting instructions that
                 are required to start a computer. It is also called non-volatile memory.

                                                                                                 ROM
                      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 as compared to primary memory.

                 Secondary memory devices are also called secondary storage devices. They are categorised into
                 three types: Magnetic disk, Optical disc and Flash drive.

                                                       Secondary Memory




                         Magnetic Disk                     Optical Disc                    Flash Drive




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



                 Magnetic Disk
                 A device, covered with a magnetic coating is called 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. 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.
                 The most important function of the hard disk is to store program
                 files and data files.                                                             Hard disk

                                             Hard disks are available in a variety of sizes with storage capacities
                                             as high as 5 TB (TeraByte) or even more. The CPU can 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.
                     External hard disk



                                                            Tech Fact

                           First hard disk was introduced by Seagate in 1979 which could hold 5 MB data.






                                                            Computer System Organization - I/O devices, Storage devices  43
   40   41   42   43   44   45   46   47   48   49   50