/*************************************************************\
 * inc - 22-08-2001 - checksum.c -- http://www.incubus.co.uk *
 * Free code, so don't come crying to me if it fouls up ||   *
 * Windows(DOS) and Linux compatable code                    *
 * Calculates a modulus 11 checksum, 6 or 5 digit weights    *
 *                                                           *
 * This code is not perfect but it does the job. I would be  *
 * grateful if you sent me improvements made to this code.   *
\*************************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/*-- Check Sum Weights --*/
#define MOD_WEIGHT_6 "65432"
#define MOD_WEIGHT_5 "5432"
#define SUCCESS 1
#define ERROR 0

int checkSum (char *value);

int main (int argc, char *argv[])
{	if (argc == 2)
	{   if(!checkSum(argv[1]))
            printf("Number incorrect length (4-5 digits only)\n");
    }
	else
	{	printf("Please enter a number with the checkdigit missing -\n");
		printf("  1234  = 5th digit will be the checkdigit\n");
        printf("  12345 = 6th digit will be the checkdigit\n");
	}
	return EXIT_SUCCESS;
}

int checkSum (char *value)
{	int count;
    int temp=0;
    int x;

	count=strlen(value);
	for (x=0; x < count; x++)
		if (count == 4)
			temp+=((value[x] -48) * (MOD_WEIGHT_5[x]-48));
		else if (count == 5)
			temp+=((value[x] -48) * (MOD_WEIGHT_6[x]-48));
		else
			return ERROR;

	count = (11-(temp%11));

    printf("Number with checkdigit appended = %s",value);
    if (count == 11)
		printf("X\n");
	else if (count == 10)
		printf("0\n");
    else
        printf("%d\n",count);
    return SUCCESS;
}