Since June 1963, a Time-Sharing System has been operational at the System Development Corporation in Santa Monica. This system was produced under the sponsorship of ARPA and has utilized ideas developed at both Massachusetts Institute of Technology and Bolt, Beranek, and Newman, as well as some original techniques. Time-sharing, in this case, means the simultaneous access to a computer by a large number of independent (and/or related) users and programs. The system is also "general purpose," since there is essentially no restriction on the kind of program that it can accommodate. The system has been used for compiling and debugging programs, conducting research, performing calculations, conducting games, and executing on-line programs using both algebraic and list-processing languages.