#include <stdio.h>

main( argc, argv ) int argc; char *argv[];

{

    unsigned source;

    int parity;

    if ( argc > 1 )
    {
        if ( sscanf( argv[1], "%d", &source ) == 1 )
        {
            printf( "%d = ", source );
            for ( parity = 0; source; parity++ )
                source &= ( source - 1 );
            printf( "%d\n", parity & 1 );
        }
    }

The function in the article is faster for > 8-bit values when there are more than eight ones in the value being checked. Also, I suppose theirs is better than K&R because it always executes in the same number of cycles.