Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!decwrl!sun!pitstop!sundc!seismo!uunet!mcvax!kth!enea!maxim!prc
From: prc@maxim.ERBE.SE (Robert Claeson)
Newsgroups: comp.arch
Subject: Re: String lengths
Message-ID: <499@maxim.ERBE.SE>
Date: 7 Feb 89 08:30:07 GMT
References: <6133@columbia.edu> <5124@aldebaran.UUCP> <7@microsoft.UUCP> <762@atanasoff.cs.iastate.edu>
Organization: ERBE DATA AB
Lines: 32

In article <762@atanasoff.cs.iastate.edu>, hascall@atanasoff.cs.iastate.edu (John Hascall) writes:

> >  - All machines I know of that have character string instructions want
> >    the length of the string. This forces the string primitives to first
> >    scan for null, a time wasting operation.

>    I assume you mean something like:

>       +------+---+---+---+---+---+---+---+---+---+---+---+---+---+
>       |length| H | E | L | L | O | , |   | W | O | R | L | D | \n|
>       +------+---+---+---+---+---+---+---+---+---+---+---+---+---+

>   but, what size would you use for "length", a byte? a word? a longword?

A 16-bit word, just to remain compatible with all the 16-bit machines
out there.

>   I suspect that some of these machines' instructions expect different
>   sized operands for the length.

Some expects 16 bits, some expects 32 bits, and a few (such as the old
Z-80) expects 8 bits.

>   Also, to quote K&R: "C was originally designed ... on the DEC PDP-11",
>   a machine with no string instructions.

Well, what can we learn from this?
-- 
Robert Claeson, ERBE DATA AB, P.O. Box 77, S-175 22 Jarfalla, Sweden
"No problems." -- Alf
Tel: +46 758-202 50  EUnet:    rclaeson@ERBE.SE  uucp:   uunet!erbe.se!rclaeson
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