TENEX (operating system)
TENEX is an operating system developed in 1969 by BBN for the PDP-10, which later formed the basis for Digital Equipment Corporation's TOPS-20 operating system. Background In the 1960s, BBN was involved in a number of LISP-based artificial intelligence projects for DARPA, many of which had very large (for the era) memory requirements. One solution to this problem was to add paging software to the LISP language, allowing it to write out unused portions of memory to disk for later recall if needed. One such system had been developed for the PDP-1 at MIT by Daniel Murphy before he joined BBN. Early DEC machines were based on an 18-bit word, allowing addresses to encode for a 256 kiloword memory. The machines were based on expensive core memory and included nowhere near the required amount. The pager used the most significant bits of the address to index a table of blocks on a magnetic drum that acted as the pager's backing store. The software would fetch the pages if needed, and then resolve the address to the proper area of RAM. In 1964 DEC announced the PDP-6. DEC was still heavily involved with MIT's AI Lab, and many feature requests from