thumb|right|250px|The CAP Computer as it currently stands in the Cambridge computer lab.
The Cambridge CAP computer was the first successful experimental computer that demonstrated the use of security capabilities, both in hardware and software. It was developed at the University of Cambridge Computer Laboratory in the 1970s. Unlike most research machines of the time, it was also a useful service machine. The memory was divided into segments of up to 64K 32-bit words. Each segment could contain data or capabilities, but not both. Hardware was accessed via an associated minicomputer.
All procedures constituting the operating system were written in ALGOL 68C, although a number of other closely associated protected procedures - such as a paginator - are written in BCPL.
Operation
The CAP first became operational in 1976. A fully functional computer, it featured a complete operating system, file system, compilers, and so on. The OS used a process tree structure, with an initial process called the "Master coordinator". This removed the need for separate modes of operation, as each process could directly access the resources of its children. In practice, only two levels were ever used during the CAP's operation.
In 1981 the MACRO SPITBOL version of the SNOBOL4 programming language was implemented on the CAP by Nicholas J. L. Brown.
See also
- Plessey System 250
- IBM System/38
- C.mmp
- RSRE Flex