FDOS

FDOS may refer to:


 * Floppy Disk Operating System, a term sometimes used to describe early floppy-based disk operating systems such as CP/M
 * FDOS, the part of the Basic Disk Operating System (BDOS) implementing the filesystem in Digital Research operating systems such as the CP/M and DR-DOS families
 * FreeDOS, a free disk operating system
 * FDOS, First Day of Service