Important Notice

The pages on this site contain documentation for very old MS-DOS software, purely for historical purposes. If you're looking for up-to-date documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.

   ◄Contents►  ◄Flags Summary►  ◄Registers Summary►  ◄Register Setup►
──────────────────────────────────────────────────────────────────────────────
 
When DOS loads an EXE program, it sets registers as follows:
 
ES        Points to segment of Program Segment Prefix (PSP)
DS        Points to segment of PSP
CS:IP     Points to CS:IP address in EXE header
SS:SP     Points to SS:SP address in EXE header
 
When DOS loads a COM program, it sets all segment registers to the
beginning of the program, and IP to 100H.
                                    -♦-