Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 exptools 1/6/84; site ihuxq.UUCP Path: utzoo!watmath!clyde!cbosgd!ihnp4!ihuxq!agk From: agk@ihuxq.UUCP (Andy Kegel) Newsgroups: net.unix-wizards Subject: Re: Csh confusion: #define HZ 100? Message-ID: <1360@ihuxq.UUCP> Date: Thu, 29-Nov-84 17:56:12 EST Article-I.D.: ihuxq.1360 Posted: Thu Nov 29 17:56:12 1984 Date-Received: Fri, 30-Nov-84 07:49:21 EST References: <124@osu-eddie.UUCP> Organization: AT&T Bell Labs, Naperville, IL Lines: 27 > We have been doing some major hacking on csh, particularly in the area > of rewriting the tcsh editor interface. (If you're interested, when > it's done, it'll edit in either vi or emacs style.) Sounds like ksh(1). > However, in > tracking down a core-dump bug which affects us only on our Suns, it was > discovered that that the symbol HZ, defined in sh.local.h, is #defined > as 100. Now, obviously, HZ is the ac line frequency; why would it ever > be 100? (Has Berkeley got some really strange power requirements?) Obviously, HZ is not the ac line frequency, but more likely related to the periodic timer. The periodic timer is commonly based on the 60 Hz line, but not always. (Horn fanfare) Enter the AT&T 3B computer line. The first 3B machine (the AT&T 3B20D computer) was designed to run without the need for AC power (continuous processing was a requirement, batteries were the solution). The designers thought it would be nice if the clock and scheduler kept running (:-), so they provided a programmable timer. Given a programmable timer, I can understand why some one would decide to count 10 millisecond units than 16.66666666666666666666666666666666666666666666 millisecond units. Now that battery powered machines are becoming more common, I expect that 60 Hz will become an interesting bit of party trivia (but then, I can expect dancing elephants and Santa Claus, too). But why #define HZ 100 ended up in csh is a mystery to me. -andy kegel just another one of them AT&T Bell Labs people with opinions of his own