Primary Arithmatic

#include<stdio.h>
#include<string.h>
int main(){

    char a[10],b[10];
    int i,j,t,len1,len2;

   gets(a);
      gets(b);

    while(a[0]!='0'||b[0]!='0'){
    int op=0,carry=0;
    len1=strlen(a);
    len2=strlen(b);
    i=len1-1;
    j=len2-1;
    while(i>=0||j>=0){
      if(i<0)t= carry+(b[j]-'0');
      else if(j<0)t=carry+(a[i]-'0');
    else t=carry+(a[i]-'0')+(b[j]-'0');
     carry=t/10;
     if(carry)
     op++;

     i--;
     j--;
        }
        if(op==0)
        printf("No carry operation\n");
        else if(op==1)
        printf("%d carry operation\n",op);
        else printf("%d carry operations\n",op);

      gets(a);
      gets(b);
        }
        return 0;
}