A computer disk is divided into tracks and sectors. The tracks are concentric circles around the disk and the sectors are segments within the circle. They look like pieces of a pie and are the smallest unit that can be accessed on a disk. A disk might have 40 tracks, for example, with each track divided into 10 sectors. Both the operating system and the disk drive keep track of where information is stored on the disk by noting its track and sector number.If a sector cannot be used due to a physical flaw,it is called a bad sector. Tracks on the outside of the disk contain more sectors than those on the inside.
In computer disk storage, the sector of a subdivision of a track on a magnetic disk or optical disk stores a fixed amount of data. Hard drives use about 4KB sectors. In order to read the data in a sector a header is needed which looks like the needle arm of an old record player. Each header has three parts: the sector head, the data head, and the error-correcting code. The sector header gives information such as address identification and an alternate address to be used if its data area is undependable. The address identification is used to be sure the read/write head is over the right spot. The data area contains the recorded user data. The ECL contains codes which are used to check for and correct errors in the data.
Shantanu
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