atoi - Converts the String to integer value in C

  #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;
  }

Output:
Enter first: 6
Enter second: 4
The sum is: 10