Q. Illustrate Layout of Magnetic Disk?

Head is a relatively small device capable of reading from or writing to a part of platter rotating beneath it. This gives rise to organization of data on platter in a concentric set of rings known as tracks. Every track is of same width as head. There are thousands of tracks for each surface.

Figure: Layout of Magnetic Disk

Figure portrays this data layout. Adjacent tracks are separated by the gaps. This avoids or at least minimizes errors because of misalignment of head. Data are transferred to and from disk in sectors. To recognize sector position generally there may be a starting point of a track and a starting and end point of every sector. However question is how a sector of a track identified is? A disk is formatted to record control data on it such that a quantity of extra data are stored on it for identical objective. This control data is accessible only to disk drive and not to user. Please note in Figure above as we move away from centre of a disk physical size of track is increasing. Does it mean we store more data on outside tracks? No. A disk rotates at a fix angular velocity. However as we diverge from centre liner velocity is more than liner velocity nearer to centre. So density of storage of information reduces as we move away from centre of disk. This results in larger physical sector size. So all sectors in disk store same amount of data.