General Structure of LISP 1.69

This is a preliminary memo describing the BBN LISP 1.69 system for the 50S 940 computer. It is a description of how the system is working now, except for those places clearly noted in the text below. Any difference between the descriptions given and actual operation found should be reported, in writing, to the authors. At the end of this memo there is a copy of the index to function descriptions in the document, "The BBN LISP SYSTEM (revised October 1966).