Listing 1 *******************************

#include <stdio.h>

main(argc, argv)
int argc;
char *argv[];
   {
   char cmd_str[81];
   if (argc > 1)
       {
       /* Fill in the length byte with the length of variable 
	   plus "set" */

       cmd_str[0] = (char ) (strlen(argv[1]) + 4);
       strcpy(&cmd_str[1],"SET ");

       /* Add the command */
       strcat(&cmd_str[1], argv[1]);
		/* Put on the carriage return */
       cmd_str[cmd_str[0] + 1] = 0X0D; 

       /* 
           Call the 0X2E interrupt.

           ds:si should point to the string.

           The first byte contains the length and 
           excludes the first byte

           The byte which follows the command is a carriage 
           return
       */
		int_2e(cmd_str);
       }
   else
       printf("\n Usage:  test  environ_variable=value\n\n No spaces");
   exit(0);
   } 

; This is the assembly language routine for the small model
.model small
.data
save_ss	dw	?
save_sp dw	?

.code
;
public _int_2e
_int_2e proc
	push	bp
	mov bp,sp
	push	si
	push	di
	push	ds
	push	es
	mov 	ax,DGROUP
	mov		ds,ax
	mov		save_sp,sp
	mov		save_ss,ss
	mov		si,[bp+4]
	int		2eh
	mov		ax,DGROUP
	mov		ds,ax
	cli
	mov		sp,save_sp
	mov		ss,save_ss
	sti
	pop		es
	pop		ds
	pop		di
	pop		si
	pop		bp
	ret
_int_2e	endp
end

			
Listing 2 ***********************************

/*  This is how you could call the interrupt without assembly */

#include <stdio.h>

struct sregs
	{
	int ax;
	int bx;
	int cx;
	int dx;
	int si;
	int di;
	int ds;
	int es;
	} ;

char cmd_str[81];

main(argc, argv)
int argc;
char *argv[];
   {
   struct sregs reg;
   union {
   		unsigned long long_number;
   		char *pc;
   		} u;				/* For picking apart the address */
   if (argc > 1)
       {
       /* Fill in the length byte with the length of variable 
		   plus "set" */

       cmd_str[0] = (char ) (strlen(argv[1]) + 5);
       strcpy(&cmd_str[1],"SET ");
       /* Add the command */
       strcat(&cmd_str[1], argv[1]);
		/* Put on the carriage return */
       cmd_str[cmd_str[0] + 1] = 0X0D; 

       /* 
           Call the 0X2E interrupt.

           ds:si should point to the string.

           The first byte contains the length and 
           excludes the first byte

           The byte which follows the command is a carriage 
           return
       */


	   	/* Pick apart the address into segment/offset */
		u.pc = cmd_str;
		reg.ds = u.long_number >> 16;
		reg.si = u.long_number & 0XFFFF;
		reg.es = reg.ds;
		reg.di = reg.di;

		sysint(0X2E, &reg, &reg);

       }
   else
       printf("\n Usage:  test  environ_variable=value\n\n No spaces");
   exit(0);
   } 





       #include <stdio.h>

       FILE *file_out;
       FILE *printer;
       FILE *disk_file;
       #define SCREEN 0
       #define PRINTER 1
       #define DISK 2

       initialize()
            {
            printer = fopen("PRN","w");                
            disk_file = fopen("TEMP","w");
           ...
           }

       switch_output(to_where)
       int to_where;           /* Where to go to */
           {
           switch(to_where)
               {
           case PRINTER:
               file_out = printer;
               break;
           case DISK:
               file_out = disk_file;
               break;
           case SCREEN:
               file_out = stdout;      /* This is the screen */
               break;
               }
           return;
           }

       /*  Somewhere in your program */

           printf("\n Going to printer");
           switch_output(PRINTER);
               ....
           fprintf(file_out, "Output");