Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!julius.cs.uiuc.edu!ux1.cso.uiuc.edu!aries!mcdonald From: mcdonald@aries.scs.uiuc.edu (Doug McDonald) Newsgroups: comp.lang.c Subject: Re: Unix and C Message-ID: <1990Nov8.152413.10792@ux1.cso.uiuc.edu> Date: 8 Nov 90 15:24:13 GMT References: <4458@mint39.UUCP> <1990Nov8.100816.6004@ericsson.se> Sender: news@ux1.cso.uiuc.edu (News) Organization: School of Chemical Sciences, Univ. of Illinois at Urbana-Champaign Lines: 24 In article <1990Nov8.100816.6004@ericsson.se> epames@eos.ericsson.se writes: >> >Of course the whole of Unix cannot be written in C but only a small >percentage need be written in assembler. It is true that an OS cannot be written entirely 100% in conformant ANSI C in general. However, for some processors it probably CAN be written in an UNHOSTED ANSI C with the only "extension" being that you can be sure that you know exactly what constructs like *((volatile unsigned char *)12345) = 6789; will in fact do (down to the coding level, such as how the mov instruction would be used. Perhaps a couple of pragmas would help. Some PDP-11 processors are probably in this class. I can think of only one obvious problem - many have a Processor Status register that requires special instructions to access. Processors that have special IO instructions of course exist - there indeed C alone cannot an operating system create. Doug McDonald