/* The BIOS INT 15 option 88H provides the total available extended 
memory in KBytes size in AX register. This program must be used only on 286 and higher PCs */
        #include <stdio.h>
	#include <dos.h>
 	main()
 	{
 	int extmem;
 	union REGS regin,regout;
 	regin.h.ah=0x88;	/* option 88H */
 	int86(0x15,&regin,&regout); /* of BIOS INT 15H */
 	extmem=regout.x.ax;
 	printf("The available extended memory is %d KB \n",extmem);
	}