Atari TOS

(The Operating System)

Atari TOS is the operating system released in 1995 by Atari for its 16/32 bits computer series.

At first, Atari had licenced both CP/M 68k (lower layer operating system) and GEM (upper layer graphical extension) from Digital Research Inc. As CP/M 68k prooved to be too slow when accessing floppy disks, Atari decided to write its own lower layer from scratch, GEMDOS based on the next and faster operating system standard, i.e. MS-DOS. This is why GEMDOS is compatible with MS-DOS FAT? filesystem.

This mixture of GEM by Digital Research and GEMDOS by Atari was named TOS, for Tramiel Operating System, and later became The Operating System.

Below GEMDOS, Atari also wrote BIOS and XBIOS responsible for dealing with Atari hardware. Within the higher layer of TOS, Digital Research had already divided GEM in a lower layer called VDI and a higher one, built on the latter and called AES. See the TOS Desing section for an in-depth discussion of TOS architecture.

Between 1985 and 1995, many TOS versions have been released, shipping different versions of the embedded system layers (GemDos, VDI, AES). For concision, these TOS versions are discussed and listed in a separate article.

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