C/stdlib.h/atol
atol: converts the string into a long int value
//Declaration: long int atol(const char *str);
#include <stdlib.h>
#include <stdio.h>
int main(void)
{
char num1[80], num2[80];
printf("Enter first: ");
gets(num1);
printf("Enter second: ");
gets(num2);
printf("The sum is: %ld.", atol(num1)+atol(num2));
return 0;
}
/*
Enter first: 3
Enter second: 2
The sum is: 5.*/