Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site fortune.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxl!ihnp4!fortune!rpw3 From: rpw3@fortune.UUCP Newsgroups: net.unix-wizards Subject: Re: Terminal paging in the kernel - (nf) Message-ID: <2767@fortune.UUCP> Date: Fri, 16-Mar-84 07:05:57 EST Article-I.D.: fortune.2767 Posted: Fri Mar 16 07:05:57 1984 Date-Received: Sat, 17-Mar-84 02:41:46 EST Sender: notes@fortune.UUCP Organization: Fortune Systems, Redwood City, CA Lines: 25 #R:cca:-684100:fortune:11600071:000:1092 fortune!rpw3 Mar 16 01:53:00 1984 I agree with Steve Zimmerman -- paging in the kernel with parameter-setting in "stty". Notice that this obeys the VERY IMPORTANT software design principle called "separation of policy and mechanism". Here, "stty" sets policy, all the kernel does is implement it. Other examples: operating systems which put only a low-level process switcher in the kernel and put the long-term scheduler and swapper in user mode; network protocols which put the data moving in the kernel but put session control in user mode; systems which put the magtape driver in the kernel but all of the label handling and volume switching in user mode; error-flagging vs. error- logging and reporting; process accounting vs. logging and reporting; etc, etc. The key is that as long as the mechanism is clean (and general) enough, one can implement many policies on it. How many different UNIX shells have there been? They all use "fork" and "exec". Rob Warnock UUCP: {sri-unix,amd70,hpda,harpo,ihnp4,allegra}!fortune!rpw3 DDD: (415)595-8444 USPS: Fortune Systems Corp, 101 Twin Dolphin Drive, Redwood City, CA 94065