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From: jack@vu44.UUCP (Jack Jansen)
Newsgroups: net.lang.c
Subject: Re:  Help with malloc(): datum ** and [i][j]
Message-ID: <374@vu44.UUCP>
Date: Tue, 28-Aug-84 02:35:47 EDT
Article-I.D.: vu44.374
Posted: Tue Aug 28 02:35:47 1984
Date-Received: Thu, 30-Aug-84 08:43:57 EDT
References: <12365@sri-arpa.UUCP> <461@sjuvax.UUCP> <8131@umcp-cs.UUCP>
Organization: VU Informatica, Amsterdam
Lines: 17

Chris Torek:
> Think of it this way:  suppose the array is declared as
> 
> 	int a[20][50];
> 
> Suppose we're asked to fetch a[6][4]. ....
> 
> The other way we could do it is multiply the 4 times the 50 and add
> 6; that is, start with the second subscript and multiply it by the
> second subscript size, then add the first subscript.  From here we
> do the same thing as before.  So add 206 to ``a'' and fetch from there.
> If I haven't got them reversed this is ``column major'' order.
Sorry Chris, but I think this is wrong. What you should do is
multiply the second subscript by the *first* subscript size, 
and add the first subscript, or, in this example use 4*20+6, or 86.

	Jack Jansen, {philabs|decvax}!mcvax!vu44!jack