Problem 4-33 Modify the "Add two digit" grogram

//============================================================================
//  제출일 : 2005. 3. 12
//  작업환경 :  Windows XP SP1, VC++ 6.0, Pentium4
//  연습문제 4-33
//============================================================================

#include <iostream.h>
//using namespace std;

// Prototype Declarations
 int addThreeDigits (int num);
 int firstDigit (int);
 int secondDigit (int);
 int thirdDigit (int);

int main()
{
 cout << "Enter an integer: ";
 int number;
 cin >> number;

 int sum = addThreeDigits (number);
 cout << "\nSum of last three digits is: " << sum;
 return 0;
} //main

int addThreeDigits (int number)
{
 int result = firstDigit(number) + secondDigit(number) + thirdDigit(number);
 return result;
}

int firstDigit(int num)
{
 return (num % 10);
}

int secondDigit(int num)
{
 int result = (num / 10) % 10;
 return result;
}

int thirdDigit(int num)
{
 int result = (num /100) % 10;
 return result;
}