Thread: Adding two big numbers in c (help)

I need to rewrite a code(below) that adds and multiply two big numbers,it needs to have functions and strings as required by my teacher but i'm not that great with them so i went ahead and wrote the code without the functions,the thing is i need your help and rewrite it with functions (and keep it as loyal as the source),i appreciate all the help ya'll guys can provide me,thanks in advance.


Here is the code without functions:

Code:

 

#include<stdio.h>
#include<string.h>
int main()
{
    char str1[101];
    char str2[101];
    int i,j,k,sum,carry,l,a,b,c,d;
    while(scanf("%s %s",str1,str2)!=EOF)
    {
        a=strlen(str1);
        b=strlen(str2);
    long int str3[110]={0};
        k=0;
        carry=0;
        sum=0;
        for(i=a-1,j=b-1;;i--,j--)
        {
            c=str1[i]-'0';
            d=str2[j]-'0';
            if(j<0)
            {
                d=0;
            }
            if(i<0)
            {
                c=0;
            }
            if(i<0&&j<0)
            {
                break;
            }
            sum=c+d+carry;
            str3[k]=sum%10;
            carry=sum/10;
            k++;
        }
    printf("sum = ");
    for(l=k-1;l>=0;l--)
    {
        printf("%ld",str3[l]);
    }
    printf("\n");
    }
    return 0;
}

Try your code with 9 and 1.

BTW, your variable names are terrible!