TOPS-10
TOPS-10 System (Timesharing / Total Operating System-10) is a discontinued operating system from Digital Equipment Corporation (DEC) for the PDP-10 (or DECsystem-10) mainframe computer family. Launched in 1967, TOPS-10 evolved from the earlier "Monitor" software for the PDP-6 and PDP-10 computers; this was renamed to TOPS-10 in 1970. Overview. TOPS-10 supported shared memory and allowed the development of one of the first true multiplayer computer games. The game, called DECWAR, was a text-oriented "Star Trek" type game. Users at terminals typed in commands and fought each other in real time. TOPS-10 was also the home of the original Multi  User Dungeon, MUD, the fore runner to today's MMORPGs. Another groundbreaking application was called "FORUM". This application was perhaps the first so-called "CB Simulator" that allowed users to converse with one another in what is now known as a chat room. This application showed the potential of multi-user communication and led to the development of CompuServe's chat application. TOPS-10 had a very robust application programming interface (API) that used a mechanism called a UUO or "Unimplemented User Operation". UUOs implemented operating system calls in a way that made them look like machine instructions. The Monitor Call  API was very much ahead of its time, like most of the operating system, and made system programming on DECsystem-10s simple and powerful. The TOPS-10 scheduler supported prioritized run queues, and appended a process onto a queue depending on its priority. The system also included User file and Device independence. Commands. The following list of commands are supported by TOPS-10. History. Release history. The PDP-6 Monitor software was first released in 1964. Support for the PDP-10's KA10 processor was added to the Monitor in release 2.18 in 1967. The TOPS-10 name was first used in 1970 for release 5.01 . Release 6.01 (May 1974) was the first TOPS-10 to implement virtual memory (demand paging), enabling programs larger than physical memory to be run. From release 7.00 onwards, symmetrical multiprocessing was available (as opposed to the master/slave arrangement used before). The final release of TOPS-10 was 7.04 in 1988. TOPS-10 today. Hobbyists are now entitled to set up and use TOPS-10 under a Hobbyist's License. The easiest way for the hobbyist to run TOPS-10 is to acquire a suitable emulator and an operating system image. TOPS-10 may also be generated from archived original distribution "tapes". Paul Allen maintained several  publicly accessible historic computer systems, including a DECsystem-2065 running TOPS-10. Software. Implemented programming languages. The TOPS-10 assembler, MACRO-10, was bundled with the TOPS-10 distribution. The following programming languages were implemented on TOPS-10 as layered products: The following programming languages were implemented on TOPS-10 as contributions from DECUS members: Implemented user utilities. The following major user utilities were implemented on TOPS-10: Legacy. MS-DOS was heavily influenced by TOPS-10. Identical elements include three characters long file extensions, several standard extensions (for eg. EXE, TXT), the asterisk () as a wildcard, the usage of the slash () as a switch separator and more. TOPS-10