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This article is about TRIPOS, the operating system. For the name given to undergraduate degree subjects by Cambridge University, see Tripos.

TRIPOS (TRIvial Portable Operating System) is a computer operating system. Development started in 1976 at the Computer Laboratory of Cambridge University and it was headed by Dr. Martin Richards. The first version appeared in January 1978 and it originally ran on a PDP-11. Later it was ported to the Computer Automation LS14 and the Data General Nova. Work on a 68000 version started in 1981 at Bath University. MetaComCo acquired the rights to the 68000 version and continued development until TRIPOS was chosen by Commodore Amiga in March 1985 to form part of an operating system for their new computer. In July 1985, the Amiga was introduced, incorporating the TRIPOS file system in AmigaDOS.

TRIPOS provided features such as pre-emptive multi-tasking (using strict-priority scheduling), a hierarchical file system and multiple command line interpreters.

The most important TRIPOS concepts have been the non-memory-management approach (meaning no checks are performed to stop programs from using unallocated memory) and message passing by means of passing pointers instead of copying message contents. Those two concepts together allowed for sending and receiving over 1250 packets per second on a 10 MHz Motorola 68010 CPU.

Most of TRIPOS was implemented in BCPL. The kernel and device drivers were implemented in assembly language.

TRIPOS was ported to a number of machines, including the Data General Nova 2, the Computer Automation LSI4, plus Motorola 68000 and Intel 8086- based hardware. It included support for the Cambridge Ring local area network. More recently, Martin Richards produced a port of TRIPOS to run under Linux, using BCPL Cintcode.

TRIPOS is still actively maintained by Open G I Ltd. (formerly Misys Financial Systems) in Worcestershire, UK. Many British insurance brokers have a Motorola 68000 based (and latterly Linux/Intel based) TRIPOS system serving either Qume terminals or Qume terminal emulators over a Telnet style TCP/IP connection - the systems are used to run Open G I's BROOMS Application suite. Open G I have added a number of features to support the modern office such as the ability to print to Windows/SAMBA or HP JetDirect printers, and XML Integration services.

Cintpos is an experimental interpretive version of TRIPOS which runs on the Cintcode BCPL virtual machine, also developed by Martin Richards.

• The TRIPOS Operating System, M. Richards, October 1988.
• Martin Richards' Cintpos page
• A brief informal history of the Computer Laboratory
• In the beginning was CAOS