Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!rutgers!cunixf.cc.columbia.edu!cubmol!ping
From: ping@cubmol.bio.columbia.edu (Shiping Zhang)
Newsgroups: comp.lang.c
Subject: Re: sizeof and multi-dimensional arrays
Message-ID: <1991Jan6.023116.5690@cubmol.bio.columbia.edu>
Date: 6 Jan 91 02:31:16 GMT
References: <1991Jan5.050613.22303@Neon.Stanford.EDU> <fred.663069060@prisma> <4596@sactoh0.SAC.CA.US>
Reply-To: ping@cubmol.bio.columbia.edu (Shiping Zhang)
Organization: Dept. of Biology, Columbia Univ., New York, NY
Lines: 24

In article <4596@sactoh0.SAC.CA.US> jak@sactoh0.SAC.CA.US (Jay A. Konigsberg) writes:

>Also I bumped the array to "char x[5][6]" and got:
 
>sizeof(x[0])=6
>sizeof(*x)=6
>sizeof(x)=30
 
>This seems to be one of the finer differences between pointers and arrays.
...
 
>sizeof(x[0]) makes sense as it returns the total size of that dimmension
>	     of the array.
>
>sizeof(*x)   DOES NOT make sense. The size of a pointer on this machine
>	     is 4 bytes. (Note: adding "char *y; sizeof(y) does return 4).

For an array x, *x is equivalent to x[0], so sizeof(x[0]) and sizeof(*x)
should get the same number. Don't be confused with the difference
between *x and &x. *x means a point in a declaration, but not in an
expression. 

-ping