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From: jru@etn-rad.UUCP (John Unekis)
Newsgroups: comp.sources.wanted,comp.lang.c,comp.sys.ibm.pc
Subject: Re: C / IBM REQUIREMENTS......
Message-ID: <262@etn-rad.UUCP>
Date: Thu, 27-Aug-87 11:55:53 EDT
Article-I.D.: etn-rad.262
Posted: Thu Aug 27 11:55:53 1987
Date-Received: Sun, 30-Aug-87 04:10:23 EDT
References: <6050@ut-ngp.UUCP>
Reply-To: jru@etn-rad.UUCP (0000-John Unekis)
Organization: Eaton Inc. IMSD, Westlake Village, CA
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Xref: mnetor comp.sources.wanted:2069 comp.lang.c:4001 comp.sys.ibm.pc:7245

In article <6050@ut-ngp.UUCP> marshek@ut-ngp.UUCP (The Genie) writes:
>
>Anybody out there have any stuff to do a peek & poke function in C ?
>(The peek & poke of BASIC).
...
 Simple, use a pointer variable, and the large model switch on the compiler.

 char *p;    declares a pointer to a byte
 int  *p;    declares a pointer to a word

 to access a physical address, you must construct it in the form of a segment
 and offset. The segment is put in the most significant word of the pointer,
 the offset is put in the least significant part. The physical address you will
 reach is the addition of the two with the segment left shifted by four bits
 (one hex digit) i.e.
	      segment      YYYY0
	      +offset    +  xxxx
	      -------    --------
	      physical     Ynnnx
	      address

setting the pointer to a constant such as
	p = (char *) 0xA1112225;  
would reach physical address (hex) A3335
to 'peek' you would simply say      variable = *p;
to 'poke' you would say             *p = value;

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hope this helps       ihnp4!wlbr!etn-rad!jru