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From: hans@log-hb.UUCP (Hans Albertsson)
Newsgroups: net.lang.c
Subject: Re: pointer question
Message-ID: <140@log-hb.UUCP>
Date: Wed, 14-Mar-84 07:28:09 EST
Article-I.D.: log-hb.140
Posted: Wed Mar 14 07:28:09 1984
Date-Received: Sat, 17-Mar-84 02:39:13 EST
References: <7624@mgweed.UUCP>
Organization: TeleLOGIC Nyn{shamn SWEDEN
Lines: 19

[come & get it ]

	I know one machine where pointers are not just different
	length, but different data structures as well. I'm thinking
	of the DEC PDP-10, a 36-bit machine, ( VERY nice.. ) where
	most stuff gets put in an integral no. of full words, and a
	pointer	to one of these objects is 18 bits, that is a Half-word.
	
	However, characters can have one of many representations,
	usually, but not always, 7 bits each ( other usual sizes are
	5 or 6 bits ), and packed an integral no. of characters in a
	word, usually 5 7-bit char:s ( = 35 bits ) in a word. The left-
	over bit is ignored... This means that a "pointer" to a
	character string is a complex structure, containing A) the
	starting address, B) the "Byte Size" in bits plus the "Byte
	Number" you're presently looking at. It takes up MOST of a
	36-bit word.
	
	Other examples probably exist.