NIL (programming language)

New Implementation of LISP (NIL) is a programming language, a dialect of the language Lisp, developed at the Massachusetts Institute of Technology (MIT) during the 1970s, and intended to be the successor to the language Maclisp. It is a 32-bit implementation, and was in part a response to Digital Equipment Corporation's (DEC) VAX computer. The project was headed by Jon L White, with a stated goal of maintaining compatibility with MacLisp while fixing many of its problems. The Lisp language was invented in 1958 by John McCarthy while he was at Massachusetts Institute of Technology (MIT). From its inception, Lisp was closely connected with the artificial intelligence (AI) research community, especially on PDP-10 systems. The 36-bit word size of the PDP-6 and PDP-10 was influenced by the usefulness of having two Lisp 18-bit pointers in one word: "The PDP-6 project started in early 1963, as a 24-bit machine. It grew to 36 bits for LISP, a design goal." Lisp was used as the implementation of the programming language Micro Planner that was the foundation for the famous AI system SHRDLU. Lisp, in particular Maclisp (so named because it originated at MIT's project MAC) was also used to implement the Macsyma computer algebra system. In the 1970s, as AI research spawned commercial offshoots, the performance of extant Lisp systems became a growing problem. Partly because of garbage collection (Lisp would use stop-and-copy garbage collection of its single heap for memory allocation) and partly because of its representation of internal structures, Lisp became difficult to run on the memory-limited stock computer hardware of the day. This led to creating Lisp machines: dedicated hardware for running Lisp environments and programs. An alternative was to use the more powerful commodity hardware which was becoming available, especially the Digital Equipment Corporation (DEC) VAX. NIL was an implementation of Lisp developed at MIT in the mid to late 1970s, and intended to be a modern successor to Maclisp that was able to run on stock hardware, in contrast to Lisp Machine Lisp for the Lisp machines.