Path: utzoo!yunexus!davecb From: davecb@yunexus.UUCP (David Collier-Brown) Newsgroups: comp.arch Subject: Re: Self-modifying code (really bootstraps) Message-ID: <4465@yunexus.UUCP> Date: 19 Oct 89 11:58:43 GMT Article-I.D.: yunexus.4465 References: <6481@pt.cs.cmu.edu> <9175@etana.tut.fi> <672@sce.carleton.ca> Organization: York U. Computing Services Lines: 22 The ICL System 10 had an interesting boot (which used no self-modifying code whatsoever (:-)). Zero, as an instruction, was interpreted as opcode operand modifier ====== ======= ======== disk_load address_0,sector_0 and was generated when one cleared the screen (!) and pressed the execute- immediate button. Poof! The bootstrap appears. This was less desirable when someone tried to execute data, of course, but did show a fine bit of subtlety in assigning opcodes. --dave -- David Collier-Brown, | davecb@yunexus, ...!yunexus!davecb or 72 Abitibi Ave., | {toronto area...}lethe!dave Willowdale, Ontario, | Joyce C-B: CANADA. 416-223-8968 | He's so smart he's dumb.