NetNews Usenet Archive 1992 #30/NN_1992_30.iso/spool/comp/lang/c/18705

Internet Message Format | 1992-12-21 | 1.8 KB

Path: sparky!uunet!spool.mu.edu!olivea!charnel!sifon!thunder.mcrcim.mcgill.edu!sobeco!philmtl!ray
From: [e-mail] (Ray Dunn)
Newsgroups: comp.lang.c
Subject: Re: Peek/Poke in C
Message-ID: <[e-mail]>
Date: 20 Dec 92 01:16:45 GMT
References: <[e-mail]> <behrenss.724679975@hphalle6>
Organization: Not Philips.
Lines: 32

In refd article, [e-mail] (Soenke Behrens) writes:
>>[e-mail] (eric webb) writes:
>>>Hi again.. does anyone know how to do equivalent of BASIC's PEEK & POKE
>>>statements in C?
>
>Very implentation-specific. Some architectures allow something along
>the lines of
>
>char *address;
>
>address = 0x678090;
>*address = 80; /* poke $678090,80 */
>printf ("And peek gives us: %d\n",*address);

_All_ architectures allow the above constructions.  What is architecture
specific is the range of numeric addresses which are meaningful, and
whether the addresses are absolute or relative to some base or segment
start address.  This is actually no different from PEEK and POKE in the
general case.

There are even architectures in which you can address _registers_ in this
way, and of course if running on hardware that has memory mapped I/O, the
I/O ports can be accessed using the same technique too.

On the PC you can create an absolute memory address so long as you define
the pointer to be of type far.  If you don't, then in small or medium model
the address is taken to be relative to the start of the data segment.  Far
pointers can be created into other segments by using (in MSC) the FP_SEG
and FP_OFF macros.
--
Ray Dunn at home        |  Beaconsfield, Quebec  |  Phone: [phone]
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