Atari released its ST microcomputers with its own TOS (The Operating System or Tramiel Operating System), which combined the DOS-like GEMDOS and DRI's GEM (Graphical Environment Manager). The first version was released with the model 520ST in 1985. TOS was one of the first operating systems to use icons to represent files and programs as well as windows and dialog to control usage flow. Version 4.04, released in 1994, was the last official Atari version of TOS. Today, TOS remains one of the most popular OS's for emulator developers, specifically because of the availability of graphics and digital music applications, as well as video game titles that are were either available only for the Atari ST, or featured superior graphics compared to platforms such as the Commodore C64. TOS is also the origin point of some GUI ideas Apple would later use for its Mac OS operating system.