Technical Operating System
The Technical Operating System is a parody of real-life's Microsoft Disk Operating System (MSDOS). The latest version of TOS mentioned in-game is TOS 3.0. It may also be "Windchime;" both OS's released in 1998. Users of the TOS are usually refered to as "TOSsers," which is slang for a person who masturbates. On the GTA IV internet, TOS is refered to as "To$$", which is a reference to real-life's "Micro$oft" spelling on computing websites and message boards. This spelling also suggests they are very focused on making money, like Microsoft. Even though TOS is mentioned frequently on GTA IV internet, it doesn't have its own website like Eunux or Fruit does. TOS' competition is Fruit Computers. TOSsers are depicted in the GTA series as "boring", with the TOS interface showing only green text on a black background (very much like DOS), while Fruits (Fruit OS users) are depicted as exciting and/or interesting people, frequently using smilies in forums.
"TOS 3.0" may be a reference to comedy series Tosh.0