types; arbitrary-precision integers (bignums); strings; and tuples. All objects (except inums) were implemented as pointers, and their data type was determined by the block of memory into which it pointed, with a special case for small numbers (inums). Programs could be interpreted or compiled. Compiled behavior was the same as interpreted except that local variables were lexical by default in compiled code, unless declared SPECIAL, and no error checking was done for inline operations such as CAR and CDR. The Ncomplr compiler (mid-1970s) introduced fast numeric support to Lisp languages, generating machine code (instructions) for arithmetic rather than calling interpretive routines which dispatched on data type. This made Lisp arithmetic comparable in speed to Fortran for scalar operations (though Fortran array and loop implementation remained much faster). The original version was limited by the 18-bit word memory address of the PDP-10, and considerable effort was expended in keeping the implementation lean and simple. Multics Maclisp had a far larger address space, but was costly to use. When the memory and processing power of the PDP-10 were exceeded, the Lisp Machine was invented: Lisp Machine Lisp is the direct descendant of Maclisp. Several other Lisp dialects were also in use, and the need to unify the community resulted in the modern Common Lisp language. Name Maclisp was named for Project MAC, and is unrelated to Apple's Macintosh (Mac) computer, which it predates by decades or to John McCarthy. The various Lisp systems for the Macintosh have no particular similarity to Maclisp. References External links http://www.softwarepreservation.org/projects/LISP/maclisp_family/ contains a bibliography of Maclisp. John L. White. An Interim LISP User's Guide. Artificial Intelligence Memo No. 190, Project MAC, Massachusetts Institute of Technology, March 1970, 87 pages. ftp://publications.ai.mit.edu/ai-publications/pdf/AIM-190.pdf states "'MACLISP' refers to the PDP/6 implementation of the programming language LISP in use at the Artificial Intelligence Group of Project MAC." "In 1973 and 1974, David A. Moon led an effort to implement MacLisp on the Honeywell 6180 under Multics. As a part of this project he wrote the first truly comprehensive reference manual for Maclisp, which became familiarly known as the 'Moonual'." [Steele and Gabriel 1993] Jon L. White [JONL], Eric Rosen [ECR], Richard M. Stallman [RMS], Guy L. Steele Jr. [GLS], Howard I. Cannon [HIC], Bob Kerns [RWK]. LISP News. MacLisp release notes. Jon L. White. LISP: Program is Data: A Historical Perspective on MacLISP. Proceedings of the 1977 MACSYMA Users' Conference. NASA Scientific