Atari TOS

Atari TOS, whose name stands for The Operating System, is the operating system Atari Corporation built for its Atari ST line of computers, debuting with the Atari 520ST on November 20, 1985. It combines Digital Research's GEM graphical environment running on top of GEMDOS, the disk operating system layer, along with BIOS, XBIOS and Line-A graphics routines; a Desktop program provides the user-facing interface on top of these layers. TOS ran on the 520ST, 1040ST and their STF, STM, STFM and STE variants and the Mega ST and STE, while later 32 bit machines such as the TT and Falcon030 used an updated multitasking version called MultiTOS. It used a flat memory model, supported MIDI natively, and after the earliest machines ran mostly from ROM chips, letting the computer start up quickly without booting from a floppy disk. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/