k&r 2-6

#include <stdio.h>

unsigned setbits(unsigned x, unsigned p, unsigned n, unsigned y) {
  unsigned mask = (1 << n) - 1;
  unsigned rmy = mask & y;
  return (x & (~mask << (p - n + 1))) | rmy;
}

void showBits(unsigned a){
    for(int i = sizeof(a) * 8 - 1; i>= 0; i--)
        printf("%d", ( a >> i) & 1);
    printf("\n");
}

unsigned read(char ch) {
  unsigned nr;
  printf("%c=", ch); scanf("%u", &nr);
  return nr;
}

int main() {
  unsigned x, p, n, y;
  x = read('x'), p = read('p'), n = read('n'), y = read('y');

  showBits(x);
  showBits(y);

  unsigned ans = setbits(x, p, n, y);
  //printf("%u\n", ans);
  showBits(ans);

  return 0;
}