1. // average6.cpp
 2. // Averages a sequence of integers entered by the user.
 3. // The number of numbers to be averaged is decided
 4. // in advance by the user and is error-checked
 5. // to ensure that it is a positive integer.
 6. // Demonstrates count-controlled repetition.
 7. // Uses a for loop.
 8. 
 9. #include <iostream>
10. using namespace std;
11. 
12. int main()
13. {
14.    // Announce purpose of program:
15.    cout << "This program averages a sequence of integers "
16.              << "entered by the user." << endl << endl;
17. 
18.    // Ask user for length of sequence of numbers to be averaged:
19.    cout << "Enter the number of numbers to be averaged:>";
20.    int numberOfNumbers;
21.    cin >> numberOfNumbers;
22. 
23.    // Error-check length of sequence:
24.    if ( numberOfNumbers <= 0 )
25.    {
26.       cout << "The number of numbers, " << numberOfNumbers
27.              << ", is invalid.  Must be > 0." << endl;
28.       return 1;
29.    }  // if
30. 
31.    // Calculate cumulative sum of numbers entered:
32. 
33.    int sum = 0;        // cumulative sum
34.    cout << "Enter the numbers:> ";
35. 
36.    for ( int i = 0;  i < numberOfNumbers;  i++ )
37.    {
38.       // Read current input number:
39.       int number;
40.       cin >> number;
41. 
42.       // Add number to cumulative sum:
43.       sum += number;
44.    }  // for i
45. 
46.    // Compute the average and output the result:
47.    float average = (float) sum / numberOfNumbers;
48.    cout << "The average is: " << average << "." << endl;
49. 
50.    return 0;
51. }  // function main