TOS

TOS was the operating system used on the Motorola 68k based computer systems released by Atari in mid 1980's and early 1990's, the ST, Mega, TT and Falcon systems. An official explanation for the acronym was never given by Atari, but it is often said to simply mean "The Operating System", or perhaps "Tramiel Operating System", after the owner of Atari Corporation at the time, Jack Tramiel.

Characteristics

TOS is stored on non-rewritable ROM chips attached to the motherboard, giving the system an "instant on" capability. However if no disk was present (either hard or floppy) the system would usually wait a considerable time before booting to chance for one to be inserted.

The TOS ROM's contain the GEM (Graphical Environment Manager) GUI from Digital Research, and is similar to the MAC-OS "classic" GUI of the mid 1980's. Early versions of this (prior to TOS 2.06) were restricted in that additional icons could not be placed on the desktop for quick launching. Later versions were much more flexible. In addition it was possible to use any number of third party "replacement" desktops (and even complete GUI's).

TOS allows for co-operative multi-tasking. This is done by the use of "Accessories", specially designed programs that are launched on startup and accessed from the "Desk" menu. They are distinguished by having an *.acc extension and must be stored in the parent or BOOT directory on a disk or hard drive. Normal (*.PRG) programs cannot be used as accessories. Up to 6 accessories may be available on any one boot partition. Only one *.PRG program may be used at once.