Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site redwood.UUCP Path: utzoo!watmath!clyde!bonnie!akgua!sdcsvax!sdcrdcf!hplabs!hpda!fortune!rhino!redwood!rpw3 From: rpw3@redwood.UUCP (Rob Warnock) Newsgroups: net.unix-wizards Subject: Re: Virtual machines Message-ID: <103@redwood.UUCP> Date: Tue, 1-Jan-85 06:52:38 EST Article-I.D.: redwood.103 Posted: Tue Jan 1 06:52:38 1985 Date-Received: Thu, 3-Jan-85 04:38:51 EST References: <986@opus.UUCP> <13500029@ea.UUCP> <258@mhuxi.UUCP> <1277@orca.UUCP> Organization: [Consultant], Foster City, CA Lines: 33 Andrew Klossnerwrites: +--------------- | CMS is a single-user IBM 370 operating system. When it runs | stand-alone on a 370, it supports a single user. Several instances of | it can be running under CP, each in a distinct virtual machine... | | There is some user interface in CP, but not much ... it's mostly of the | "simulate a front panel" variety, like the command to boot an operating | system in your virtual machine. +--------------- I find it interesting to compare TOPS-10, which was originally (in the PDP-10/30 configuration) a single user monitor. When it became a timesharing system, the user view of a single-user system persisted. Your "job" was a virtual machine, albeit with system calls in the "hardware" (much like the later versions of CP with the extended "diagnose" call). You managed your "core image" via front-panel-like commands, such as "examine" and "deposit". It was perfectly legal to sit and type octal machine code into (your job's) core and run it. You could "get" an image, run it, halt it, patch it, and "save" it again. When a program exited, the core image was still there. In fact, certain large programs depended on this -- after compiling one of them you would run it one time so it could build its symbol tables (or whatever), then it changed its starting address and exited so you could save it with the startup code already done (a trick "ps" could use, no doubt!). Rob Warnock Systems Architecture Consultant UUCP: {ihnp4,ucbvax!dual}!fortune!redwood!rpw3 DDD: (415)572-2607 USPS: 510 Trinidad Lane, Foster City, CA 94404