Q23868: How to Do "Peeks" and "Pokes" in a C Program

Article: Q23868
Product(s): See article
Version(s): 3.00 4.00 5.00 5.10 6.00 6.00a
Operating System(s): MS-DOS
Keyword(s): ENDUSER | s_quickc | mspl13_c
Last Modified: 6-FEB-1991

The sample code below contains two functions that simulate what are
commonly known as "peek" and "poke" functions. The peek() function
allows you to look at the contents of any memory location while the
poke() function allows you to place a value into any memory location.

Sample Code
-----------

/* The following function will stuff a value into any location in
   addressable memory. seg:ofs = val.
*/

void poke(unsigned int seg, unsigned int ofs, char val)
{
    unsigned char far *ptr;

    ptr = (unsigned char far *) (((long)seg<<16)|(long)ofs);
    *ptr = val;
}

/* The following function will return the contents of any location in
   addressable memory. return(seg:ofs).
*/

unsigned char peek(unsigned int seg, unsigned int ofs)
{
    unsigned char far *ptr;

    ptr = (unsigned char far *) (((long)seg<<16)|(long)ofs);
    return(*ptr);
}

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