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Date: 09 Oct 1992 12:40:54 +0100
From: Arne Vajhxj <ARNE@ko.hhs.dk>
Reply-To: MACRO32@WKUVX1.BITNET
Subject: Re: C Language question
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> Question: in C, if one declares char a[I][J], is there anything in the
> language standard that guarantees that &a[0][0] is the first of a set of
> I*J contiguous chars, and that a[i+1][0] is guaranteed to be the same
> storage location as a[i][J] ).
>
> A friend asserts that it is, and says his experience on several systems
> 'proves' this. My belief is that there is nothing that says this will
> always be the case, and that the only constraint is that every valid pointer
> a[i] will point to J chars. Which of us is right?

I think your friend is rigth (a[I][J] would be I*J contigious bytes), but
I can not prove it, but ...

The arguments are:
  1)  As your friend has observed C-compilers tend to do it that way.
  2)  The creative way C lets you manipulate arrays, pointers and
      addresses must somehow assume, that they are stored contigious.
  3)  It is most efficient that way (simpler address calculations).

But to be absolutely certain you will need to check the real sources:
K&R and the ANSI specifications.

                                                          Arne

Arne Vajhxj                             local DECNET:  KO::ARNE
Computer Department                     PSI:           PSI%23831001304030::ARNE
Business School of Southern Denmark     Internet:      ARNE@KO.HHS.DK