Floppy disk is a pocketbook version of the magnetic disk. It is a random access device available in size 3 1/2, 5 1/4 or 8 inches diameter. Storage capacities of 640 KB, 1.2 MB, 1.44 MB are typical. It is a cheap, durable, non-volatile storage option and reusable by writing over the previous data. Floppy disk is a circular plate coated with magnetic material. It is enclosed in a jacket made of a special fiber that allows for the air to cushion the disk when it is rotating at high speed and avoid wear and tear to the disk. 

Both the floppy and the jacket carry a central hole for the central spindle and a small circular hole near it. The beginning of tracks and sectors are signaled when the small circular holes in the jacket and the disk coincide. There is a write-protect notch on the jacket, which when closed by a sticker, seals the floppy and thus prevents any further writing. Then information can only be read from the floppy.

The read-write heads sense the information through the oblong window in the jacket, which exposes the disk to the head. Floppy is to be formatted with tracks and sectors before use. Directory and file indices are stored in ‘00’ track of ‘01’ sector onwards to ‘n’ the sector and proceed to‘01’ th sector of ‘02’ track, etc., Each track holds the same volume of information. Reading commences from ‘00’ tracks and writing starts from a sector as mentioned earlier.