//Declaration: int atoi(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: %d.", atoi(num1)+atoi(num2)); return 0; } /* Enter first: 3 Enter second: 4 The sum is: 7.*/