#include <stdio.h>/* * function bit_count * Counts the number of bits on (i.e., = 1) in an unsigned int * (This code assumes that an int is 32-bits!) * Parameter: *   x - number to count bits of * Return value: *   number of bits on in x */int bit_count(unsigned int x ){  static unsigned int mask[] = { 0x55555555,                                 0x33333333,                                 0x0F0F0F0F,                                 0x00FF00FF,                                 0x0000FFFF };  int i;  int shift;   /* number of positions to shift to right */  for( i=0, shift=1; i < 5; i++, shift *= 2 )    x = (x & mask[i]) + ( (x >> shift) & mask[i] );  return x;}int main(){  unsigned int x;  printf("Enter a number: ");  scanf("%i", &x);  printf("There are %d bits on in %X\n", bit_count(x), x);  return 0;}