判断二进制位上1个数量

main()
{
 unsigned x;
 int a,num;

 printf("put in a number:/n");
 scanf("%u",&x);

/*方法1:*/

 for(num=0,a=1;a!=0;a<<=1)
  if(a&x) ++num;
 printf("/nthe number of 1 is :%d/n",num);

/*方法二: */

 for(num=0,a=1;x!=0;x>>=1)
   if(a&x) ++num;

  printf("/nthe number of 1 is:%d/n",num);
}