Subject:
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Re: Help with pointers
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Thu, 25 Mar 1999 18:42:18 GMT
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Original-From:
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Keith Hearn <khearn@STOPSPAMlegato.com>
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Viewed:
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1039 times
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In message <36FA5DB7.32ABEF8@zhwin.ch>, Thomas Hauri writes:
> Hi all
> little question:
>
> How can I ad a value to a pointer ??
>
> int *px, x;
>
> px = &x;
>
> px = px + 1; (????? pointing to the lowbyte of x for example)
When you do pointer arithmatic, you work in increments of what the
pointer points to. So if you have a pointer to an int, as in the above
example, when you add one to it, you actually make it point to the
next int, not the next byte or word.
This is so that you can have an array of something and move a pointer
through the array by ioncrementing it without having to pay
attention to how big your array elements are.
If you want to point to the low byte of x, you might be able to do
something like this:
int x;
char * p; /*this assumes that a char is one byte*/
p = &x;
p++;
Be warned that that is pretty non-portable code. What it actually does
depends on how big int and char are with the specific
compiler/machine combination, and details like byte ordering within
words.
The above all applies to "normal" C. I'm not exactl sure how IC would
handle it.
Keith Hearn
khearn@legato.com
>
> Is it just NOT possible with IC or am I missunderstanding anything ????
>
> Thanks for any help.
>
> --
> Thomas Hauri
> ZHW Zuercher Hochschule Winterthur
> University of applied sciences
> Technikumstr.9 /PF
> CH-8401 Winterthur
> Switzerland
>
> Phone : +41 52 267 74 79
> Fax : +41 52 268 74 79
> Mail : Thomas.Hauri@zhwin.ch
> HP : http://www.zhwin.ch
>
>
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Message is in Reply To:
 | | Help with pointers
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| Hi all little question: How can I ad a value to a pointer ?? int *px, x; px = &x; px = px + 1; (????? pointing to the lowbyte of x for example) Is it just NOT possible with IC or am I missunderstanding anything ???? Thanks for any help. -- Thomas (...) (26 years ago, 25-Mar-99, to lugnet.robotics.handyboard)
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