single opertaing system

You need to format a floppy disk in order to be able to use it, you cannot write to a floppy disk otherwise. Normally the disk would already be formatted when you purchase it so most people never see the need to bother. A quick format will simply rebuild the header file but leave data on the disk, whereas a full format will remove all previous data from the disk and leave a totally clean disk for future use.

Read in here http://www.vfrazee.com/ms-dos/6.22/help/format.htm