Apple DOS 3.1 disks use 13 sectors of data per track, each sector being 256 B. It uses 35 tracks per disk side, and can access only one side of the floppy disk, unless the user flipped the disk over. This gives the user a total storage capacity of 113.75 KB per side, of which about 10 KB are used to store DOS itself and the disk directory, leaving about 100 KB for user programs.