Re: Interesting. Circa 1973, Bill Gord and I wrote a BBN-LISP to p-code compiler and interpreter on a Burroughs B6500 for the UCSD (University of California, San Diego) Computer Center, on a contract for DARPA. (BBN-LISP is the precursor to InterLISP.) BBN-LISP didn't have the p-code stuff. Our DARPA contract was to port BBN-LISP to the B6500; once we got the LISP interpreter running, we then decided to improve the speed by doing the UCSD-unique enhancement of the compiler/interpreter. IIRC, this pre-dated UCSD Pascal p-code, but there's an obvious relationship: Bill and I worked for Ken Bowles, and both p-codes (and Java byte code :) resemble the B6500 instruction set. My recollection is that I wrote the LISP-to-p-code compiler (in LISP, of course :), and Bill designed the p-code and wrote the p-code interpreter (in Burroughs ALGOL). When interpreting a LISP function, we would jump to the p-code interpreter if the function had been compiled, otherwise we'd stay in the LISP interpreter code. We talked about writing a p-code to machine code translator, but in those days the Burroughs B6500 MCP code/data separation would have made aspects of the implementation inefficient, so we never did that. Stan Sieler -- Stan Sieler sieler at allegro.com www.allegro.com/sieler/wanted/index.html