Counting number of 1's and 0's from integer with bitwise operation

Is there a better way of doing this?

// Definition: Count number of 1's and 0's from integer with bitwise operation
//
// 2^32 = 4,294,967,296
// unsigned int 32 bit

#include

int CountOnesFromInteger(unsigned int);

int main()
{
    unsigned int inputValue;
    short unsigned int onesOfValue;
    printf("Please Enter value (between 0 to 4,294,967,295) : ");
    scanf("%u",&inputValue);
    onesOfValue = CountOnesFromInteger(inputValue);

    printf("\nThe Number has \"%d\" 1's and \"%d\" 0's",onesOfValue,32-onesOfValue);
}

int CountOnesFromInteger(unsigned int value)
{
    unsigned short int i, count = 0;
    for(i = 0; i > 1;
    }
    return count;
}

Yes, there is a better way:

int CountOnesFromInteger(unsigned int value) {
    int count;
    for (count = 0; value != 0; count++, value &= value-1);
    return count;
}

The code relies on the fact that the expression x &= x-1; removes the rightmost bit from x that is set. We keep doing so until no more 1's are removed. This technique is described in K&R.

This approach is superior because it doesn't depend on an integer's size - it's totally portable - and it tests every bit in a fairly efficient way (with the comparison value != 0).

Also, you might want to replace 32 in main() with sizeof(int)*CHAR_BIT so that your code doesn't depend on an integer using 32 bits:

#include 
#include 

int CountOnesFromInteger(unsigned int);

int main()
{
    unsigned int inputValue;
    short unsigned int onesOfValue;
    printf("Please Enter value (between 0 to 4,294,967,295) : ");
    scanf("%u",&inputValue);
    onesOfValue = CountOnesFromInteger(inputValue);

    printf("\nThe Number has \"%d\" 1's and \"%zu\" 0's",onesOfValue,sizeof(int)*CHAR_BIT-onesOfValue);
    return 0;
}

StackExchange Code Review Q#38182, answer score: 28