ansi_c_pg47_ch02_ex07.c

/*
 * Exercise 2-7.
 * Write a function invert(x,p,n) that returns x with the n bits that begin at
 * position p inverted (i.e., 1 changed into 0 and vice versa), leaving the
 * others unchanged.
 */


#include <stdio.h>



unsigned int
invert(unsigned int x, int p, int n) {
	unsigned int mask = (~0 << (p+1-n)) ^ (~0<<(p+1));
	return x ^ mask;
}

int
main() {
	unsigned int x = 0xff;
	unsigned int y = 0x00;
	y = invert(x,2,1);
	printf ("y = %X \n", y);
}