unsigned long long to binary

Question

I am trying to check the set bits of an unsigned long long in c++ using below algorithm which only checks whether the bit is set or not.But my problem is the answer that I get is wrong.Please help me understand how unsigned long long is stored in binary.

Code:

#include<stdio.h>
#include<iostream>
#define CHECK_BIT(var,pos) ((var) & (1<<(pos)))
using namespace std;
int main()
{
    int pos=sizeof(unsigned long long)*8;
    unsigned long long a;
    cin>>a;
    pos=pos-1;
    while(pos>=0)
    {
        if(CHECK_BIT(a,pos))
          cout<<"1";
        else
          cout<<"0";
        --pos;
    }
}

Input :

1000000000000000000

Output:

1010011101100100000000000000000010100111011001000000000000000000

Expected Output:

110111100000101101101011001110100111011001000000000000000000

Similarly for another input:

14141

Output :

0000000000000000001101110011110100000000000000000011011100111101

Expected Output:

11011100111101

In the second example(in fact for any small number) the binary pattern just repeats itself after 32 bits.

Answer 1

I think what you have is an issue in the bit set macro , please replace it w/

#define CHECK_BIT(var,pos) ((var) & (1LL<<(pos)))