Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!husc6!rutgers!rochester!pt!k.cs.cmu.edu!lindsay From: lindsay@k.cs.cmu.edu (Donald Lindsay) Newsgroups: comp.arch Subject: Re: machine word sizes Message-ID: <1184@k.cs.cmu.edu> Date: Fri, 24-Jul-87 11:16:58 EDT Article-I.D.: k.1184 Posted: Fri Jul 24 11:16:58 1987 Date-Received: Sat, 25-Jul-87 15:52:14 EDT References: <142700010@tiger.UUCP> <2792@phri.UUCP> <8315@utzoo.UUCP> <2807@phri.UUCP> <565@saturn.ucsc.edu> Organization: Carnegie-Mellon University, CS/RI Lines: 12 I believe that John Von Neumann chose 36 bits as giving the precision he wanted for arithmetic calculation. This was in the early 1950's, when floating point hardware was too expensive to be worthwhile. Twelve bit machines, such as the PDP-8, were used as lab machines. The best analog-to-digital converters (ADCs) were 12 bits at that time. Perhaps some 24-bit machines relate to this. The PDP-5, 7, 9, and 15 were 18 bit machines ( 36/2 I'm sure ). The most visible result of this is the silly tendency to use six-and-three characters for filenames ( "myfile.bas" ).