Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!husc6!necntc!ames!ucbcad!ucbvax!hplabs!hpcea!hpccc!kevino
From: kevino@hpccc.HP.COM (Kevin Owen)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Looking for C functions to access PC memory
Message-ID: <5060012@hpccc.HP.COM>
Date: Tue, 10-Nov-87 23:35:16 EST
Article-I.D.: hpccc.5060012
Posted: Tue Nov 10 23:35:16 1987
Date-Received: Sun, 15-Nov-87 03:28:51 EST
References: <24261F3U@PSUVMB>
Organization: HP Corporate Computing Center
Lines: 55

/ hpccc:comp.sys.ibm.pc / luis@grinch.UUCP (luis) /  8:43 pm  Nov  7, 1987 /
In article <447@ucdavis.ucdavis.edu> kwok@iris.UUCP (Conrad Kwok) writes:
>When you are using C, you don't need any special routine to read
>memory. All you need to do is to declare a pointer (near or far
>depending on the address) and then you may read or write to that
>location using normal assignment statements. Here is an example to
>read the value at location 0xC000:0x0100
>
>	char far *ptr;
>
>	ptr = (char far *) 0xC0000100L;
>	printf("Value at 0xC000:0x0100 is %d\n", *ptr);
>
>[...]

Thank you for posting the example, but I have a few questions...
  1. Why is there an 'L' at the end of the address?  (does it stand for Long?)
  2. I have been trying to access the DTR on my modem, but I don't know
     what the base address is.  From the Technical Reference, I know that
     the offset is 3FE (bit 0), but can't find the base addres..  Can anyone
     help?

-------------------------------------------------------------------------------
Luis Chanu                             "Live every day as if it were your last,
UUCP: ...ihnp4!sun!aeras!grinch!luis      because one day you will be right."
UUCP: ...pyramid!wjvax!grinch!luis                              -Benny Hill
              Disk-Claimer: That's not your disk, that's my disk.
-------------------------------------------------------------------------------
----------

While I did not post the above response I thought I might take a stab at 
addressing your questions. 

You are correct that L indicates long.  As for your second question - you 
need to use inp() and outp() to be able to access your serial port.

Both serial and parallel ports on a PC are considered to reside in I/O space
and cannot be accessed using memory references.  

A sample code fragment follows :
------------------------------------

#include <conio.h>

unsigned port = 0x3fe;
char result;

result = inp(port);       /* Result now contains the byte input from port 3fe */
printf("DTR is %s\n",(result & 0x01) ? "HIGH" : "LOW");

------------------------------------

I hope this helps...

Regards,  Kevin Owen