Physical disk geometry ------is a way of describing the disk's structure to make it readable by the system BIOS.It consists of the number of cylinders per disk,the number of read/write heads per cylinder,and the number of sectors per track.
A cylinder refers to all tracks accessible from a single position of the read/write heads.A file is initially stored on a disk using adjacent cylinders.This reduces the amout of movement by the read-write heads.
A sector is a 512-byte portion of a track..
Fragmentation------over time,as files become more spread out around a disk,they become fragmented.A fragmented file is one whose sectors are no longer located in contiguous areas of the disk. When this happens, the read-write heads have to skip across tracks when reading the file's data. This slows down the reading and writing of files, and makes the data more susceptible to errors.
