cfunc.c

ART OF Assembly Language Programming, 很不错

#include <stdlib.h>
#include <stdio.h>


/* Generic logic function.  The "Func" parameter contains the 16-bit 	*/
/* logical function number.  This is actually an encoded truth table	*/
/* for the function.  The a, b, c, and d parameters are the inputs to	*/
/* the logic function.  If we treat "func" as a 2x2x2x2 array of bits,	*/
/* this particular function selects bit "func[d,c,b,a]" from func.	*/

int
generic(int func, int a, int b, int c, int d)
{
	return (func >> (a + b*2 + c*4 + d*8)) & 1;
}

/* Main program to drive the generic logic function written in C.	*/

main()
{
	int func, a, b, c, d;

	do
	{
		printf("Enter function value (hex): ");
		scanf("%x", &func);
		if (func != 0)
		{
			printf("Enter values for d, c, b, & a: ");
			scanf("%d%d%d%d",
				&d, &c, &b, &a);

			printf("The result is %d\n", generic(func,a,b,c,d));
			printf("Func = %x, A=%d, B=%d, C=%d, D=%d\n",
				func, a, b, c, d);
		}
	} while (func !=0);

}