 Consequently, all the file management functions are centralized in the "OS"-part, and the "DOS"-part is only one of its subordinated device drivers, that performs on a mass-storage media (like floppy disk).A "DOS" for Atari, then, typically consists of the aforementioned device driver (called FMS, "File Management System"), and an application program playing the role of the OS shell.This shell is typically called DUP, "Disk Utility Package".