// CS 350, Illinois Inst Tech, J. Sasaki
// Lecture 8, Spring 2012
//
// Bit selection examples in C
//
#include <stdio.h>

int main(void) {

	int x = 0x12345678, y = 0xcdef0123;

	// For printing:
	// %x   -- print in hex (as many characters as necessary)
	// %08x -- print zero-filled, >= 8 characters, in hex
	//
	printf("%x &  %x = %08x (bitwise and)\n", x, y, x & y);
	printf("%x |  %x = %08x (bitwise or)\n", x, y, x | y);
	printf("%x ^  %x = %08x (bitwise xor)\n", x, y, x ^ y);
	printf("\n");

	printf("%x && %x = %d (logical and)\n", x, y, x && y);
	printf("%x || %x = %d (logical or)\n", x, y, x || y);
	printf("\n");

	printf("!! %x = %d,  !! %x = %d\n", x, !!x, y, !!y);
	printf("\n");

	printf("   %x !=    %x = %d (inequality)\n", x, y, x != y);
	printf("!! %x != !! %x = %d (logical xor)\n", x, y, !!x != !!y);
	printf("\n");


	// Using xor's properties of associativity, commutativity, and N ^ N = 0,
	// we can swap two variables without using a temporary location.
	//
	// Note: x ^= y means x = x ^ y.  (Also exist &= and |= operators)
    //
	printf("x = %x, y = %x\n", x, y);
				// Say x = A and y = B
	x ^= y;		// Now x = A^B,  y = B
	y ^= x;		// x = A^B,  y = B^(A^B) = (B^B)^A = 0^A = A
	x ^= y;		// x = (A^B)^A = (A^A)^B = B,  y = A
	printf("x = %x, y = %x after x ^= y; y ^= x; x ^= y\n", x, y);
	printf("\n");

	int bitnbr = 2;
	int mask = 1 << bitnbr;		// << is left shift, >> is right shift
	int value = 0x01234563;
	printf("%08x | %08x = %08x (set bit %d)\n", value, mask, value | mask, bitnbr);

	value = 0x01234567;
	printf("%08x & %08x = %08x (select bit %d)\n", value, mask, value & mask, bitnbr);

	value = 0xffffffff;
	printf("%08x ^ %08x = %08x (reverse mask %d)\n", value, mask, value ^ mask, bitnbr);

	int reverse_mask = 0xffffffff ^ mask;
	value = 0x0123cdef;
	printf("%08x & %08x = %08x (unset bit %d)\n", value, reverse_mask, value & reverse_mask, bitnbr);

	return 0;
}