From clc-wiki

The C Programming Language, 2nd Edition, by Kernighan and Ritchie
Exercise 2.07 on page 49

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.

Solution by Gregory Pietsch

unsigned invert(unsigned x, int p, int n)
{
    return x ^ (~(~0U << n) << p);
}

/*
main driver added, in a hurry while tired, by RJH. Better test driver suggestions are welcomed!

main driver fixed by Flash Gordon as it was passing the parameters in the wrong order and
hex is a more useful output format than decimal for checking the result. Also start at 0
for n,p as they are valid inputs.
*/

#include <stdio.h>

int main(void)
{
  unsigned x;
  int p, n;

  for(x = 0; x < 700; x += 49)
    for(n = 0; n < 8; n++)
      for(p = 0; p < 8; p++)
        printf("%x, %d, %d: %x\n", x, p, n, invert(x, p, n));
  return 0;
}