_mul32

mul32.c

/*
 * Multiplies two 32-bit numbers on 8086.
 */
long _stdcall _mul32(int highr, int lowr, int highl, int lowl)
{
	asm {
		
		; a = lowl * lowr
		mov ax, [bp + 6] ; lowl
		mul word [bp + 10] ; lowr
		mov bx, ax ; lowa  in bx
		mov cx, dx ; higha in cx
		
		; a +=
		; (lowl * highr) << 16
		mov ax, [bp + 6]
		mul word [bp + 4]
		add cx, dx
		
		; a +=
		; (highl * lowr) << 16
		mov ax, [bp + 8]
		mul word [bp + 6]
		add cx, dx
		
		mov ax, bx
		mov dx, cx

	}
}