#include <iostream>
#include <cmath>
#include <iomanip>

int main()
{
    unsigned i, k, mask;
    i=1891;
    mask = 0xff;
    k = i & mask;
    std::cout << std::hex << "i, mask, k ="<<
     i << ", "<< mask << ", "<< k <<   std::endl;

    mask = mask | 0xf00;
    k = i & mask;
    std::cout << std::hex << "i, mask, k ="<<
     i << ", "<< mask << ", "<< k <<   std::endl;

    mask = 0x1 << 8 ;  // set 9th bit from LSB
    k = i & mask;
    std::cout << std::hex << "i, mask, k ="<<
     i << ", "<< mask << ", "<< k <<   std::endl;
     return(0);
}

$ ./a.exe
i, mask, k =763, ff, 63
i, mask, k =763, fff, 763
i, mask, k =763, 100, 100