How many bits are '1' in an integer variable?

[cuthbert]

Hi folks,

I am trying to find a more efficient way to count "How many bits are
'1' in an integer variable?".

I still have no idea to count the bits except using a loop and "if"
statements.
Could you know any other more efficient way?

Cuthbert

int main (void)
{
int var = 0xFF0F;
int i, count = 0;
int mask = 1;
for ( i = 0; i < sizeof(int)*8 ; i++ )
if ( mask<<i & var) count++ ;

printf("%d\n", count);

return 0;
}