Here are few ways using which addition can be performed without the use of arithmetic operator '+'.

1. Recursion

int add(int, int);
int main() {
   int num1, num2;

   printf("\nEnter the two Numbers : ");
   scanf("%d %d", &num1, &num2);

   printf("\nAddition of two num is : %d", add(num1, num2));
   return (0);
}

int add(int num1, int num2) {
   if (!num1)
      return num2;
   else
      return add((num1 & num2) << 1, num1 ^ num2);
}

2. Looping 1

int main() {
   int num1 = 10, num2 = 5, i;

   while (num2 > 0) {
      num1++;
      num2--;
   }

   printf("%d", num1);
   return (0);
}

3. Looping 2

int main() {
int num1 = 10, num2 = 5, i;

while (num2--) {
num1++;
}

printf("Sum is : %d", num1);
return (0);
}

4. Looping 3

int sum(int, int);
int main() {
   int a, b;

   printf("Enter the two Numbers: ");
   scanf("%d %d", &a, &b);

   printf("Addition of two num. is : %d", add(a, b));
   return(0);
}

int add(int num1, int num2) {
   int i;
   for (i = 0; i < num2; i++)
      num1++;
   return num1;
}

5. Using Subtraction for Addition!

int main() {
   int num1 = 10, num2 = 5;

   num1 = num1 - (-num2);
   printf("Sum is : %d",num1);

   return (0);
}

I hope this note would be helpful to all. Do share your views and comments.

Note: Header files are not included in above code.