A computer is complete and is ready to work if it has three basic units that are input unit, output unit and central processing unit. But to increase its speed and make it more reliable and efficient secondary storage devices are attached to it and this secondary memory needs a drive for reading and writing to related secondary storage device. Actually the memory inside CPU is primary memory but the secondary memory is unlimited and is a permanent storage space. However the data stored on it may not be used directly without transferring them to the primary memory even then it is very useful because of the fact that information can be stored on it as long as you require and you can use as much second memory as you need. Various secondary storage devices are floppy disks, hard disks, magnetic tapes, compact disks, DVD’s, punched cards, punched paper tapes and latest disk that is blue ray disk which can store very large amount of data.
Data can be stored on these secondary storage devices according to need but the problem that arises here is how to read from and write to it. For this the input/output devices like disk drives are used reading and writing on a floppy diskette is done using floppy disk drive. Hard disk needs. Hard disk drive, CD-ROM needs CD drives and magnetic tapes need tape drives. All the drives perform both the jobs of input and output.
Floppy disk drives: - Floppy disk is a small storage disk. For storing data and accessing data from the floppy disks we need an input device with read write data. The floppy disk drives solve this purpose. They are available with almost all the computers. As according to size of disks there are three sizes of disk drives available. They are 8 inch drive, 5 ¼ inch drive and 3 ½ drive.
Hard Disk Drive: - The hard disk is used to store information permanently inside the computer. It is not a volatile memory as computer’s main memory. It is some how similar to floppy disks. It is some times called as hard drive or hard disk drive, the original hard disk made by IBM we called Winchester and thus hard disks are also known as Winchester disks. It is a high volume and high speed data storage used in PC. The floppies provide easy and inexpensive storage medium but they are slow and some times a long program or software may not be stored on a single floppy. This problem gave birth to hard disk. In modern computers hard disk has become an indispensable element.
CD Drive: - CD ROM is an acronym for Compact Disk Read only memory. It is a digital optical mass storage device which has a capacity of 550 MB on a single disk. Now almost all major software are distributed on CD’s and hence they have emerged as an absolute necessity to modern computer. A CD-ROM drive is very reliable device which does not require maintenance like other devices. They are also inexpensive devices.
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