Reverse Bits ( 16 bit )

int main( void )
{
    int a= 0xFF00, i, rev=0;

    for( i = 0; i < 16; ++i )
    {
        if( a & ( 1 << i ) )
        {
            rev |= ( 0x8000 >> i );
        }
    }
    printf( "Input is 0x%04x\n", a );
    printf( "Reverse Bit Is 0x%04x\n", rev );

    return 0;
}