with DOS/4GW? - Open Watcom

DOS Programming Guide
0x0021 function to create a directory. The string of characters are used to provide the
directory name. This example can be adapted to handle most real-mode interrupt calls that
aren’t supported in protected mode.
/*
SIMULATE.C - Shows how to issue a real-mode interrupt
from protected mode using DPMI call 300h. Any buffers
to be passed to DOS must be allocated in DOS memory
This can be done with DPMI call 100h. This program
will call DOS int 21, function 39h, "Create
Directory".
Compile & Link: wcl386 /l=dos4g simulate
*/
#include
#include
#include
#include
static struct rminfo {
long EDI;
long ESI;
long EBP;
long reserved by system;
long EBX;
long EDX;
long ECX;
long EAX;
short flags;
short ES,DS,FS,GS,IP,CS,SP,SS;
} RMI;
void main()
{
union REGS regs;
struct SREGS sregs;
int interrupt no=0x31;
short selector;
short segment;
char far *str;
/* DPMI call 100h allocates DOS memory */
memset(&sregs,0,sizeof(sregs));
regs.w.ax=0x0100;
regs.w.bx=0x0001;
int386x( interrupt no, &regs, &regs, &sregs);
segment=regs.w.ax;
selector=regs.w.dx;
/* Move string to DOS real-mode memory */
str=MK FP(selector,0);
fstrcpy( str, "myjunk" );
/* Set up real-mode call structure */
memset(&RMI,0,sizeof(RMI));
RMI.EAX=0x00003900; /* call service 39h ah=0x39 */
RMI.DS=segment; /* put DOS seg:off into DS:DX*/
RMI.EDX=0; /* DOS ignores EDX high word */
36 How Do I Simulate a Real-Mode Interrupt with DOS/4GW?