Introduction to Operating System

Disks and Drives

Because most of our computers Memory (RAM) is temporary, its contents are erased when we switch off the power. We need a place to store the Operating System, application programs and our work. That's where disks come in, we store any information you want to keep onto disks.   There are two types of disk: 1. Floppy disks & 2. Hard disks.     1. Floppy disks (Diskettes) A disk is a magnetically coated disk of thin plastic, inside a rigid plastic cover.   We can use Floppy disks to: . Transfer information from one computer to another. . Store the Operating System, or application program and our work, if we don't have a Hard disk. . Keep a copy of information that we have on our Hard disk (Backup).   We need only format a disk once. After that, we can use the disk again and again without having to reformat it. Formatting a disk we have previously used erases any data on the disk, so only reformat a disk if we are sure we don't need any of the data on it.     Choosing disks Diskettes come in various forms, so it is important to choose diskettes that match the type of diskette drive installed in our computer.   Several different types are available: . 5.25inch 360 Kbytes - Very rarely used now . 5.25inch 1.2 Mbytes - Uncommon but still in use . 3.5inch 720 Kbytes - Getting less common, still in use . 3.5inch 1.44 Mbytes - The standard in most modern computers.

It should be noted that:- . A 720 Kbytes drive can only read and write to a 720 Kbytes diskette . A 1.44 Mbyte drive can read and write to both 720 Kbytes and 1.44 Mbyte diskettes. However we must use special formatting instructions to format a 720 Kbytes diskette in a 1.44 Mbyte drive. . The visible difference between a 720 Kbytes diskette and a 1.44 Mbyte diskette is that there is no extra notch on a 720 Kbytes diskette.     2. Hard disks A Hard disk is a disk that is enclosed in a permanently sealed metal housing.   Hard disks are better than Floppy diskettes in two main respects: . We can store much more information on a Hard disk than on a diskette. For example, a 40 Mbyte Hard disk holds the equivalent of almost twenty nine 1.44 Mbyte Floppy diskettes.   . They are up to 600 times faster at finding and loading information into the computers Memory.