C Coding Style

error.h

#define SUCCESS     0
#define NULL_ARGS   1
#define NULL_PARAM -1

main.c

#include <stdio.h>

#include "error.h"

int unsigned_sum( const unsigned int& x, const unsigned int& y );

int main( int argc, char* argv[] )
{
    if( argc != 0 )
    {
        unsigned int a, b;
        unsigned_sum( a, b );
        return SUCCESS;
    } else {
        return NULL_ARGS;
    }
}

int unsigned_sum( const unsigned int& x, const unsigned int& y )
{
    if( !x || !y )
    {
        return NULL_PARAM;
    }

    return x + y;
}