1. // FunctionDemo - demonstrate the use of functions
2. //                by breaking the inner loop of the
3. //                NestedDemo program off into its own
4. //                function
5. 
6. #include <stdio.h> 
7. #include <iostream.h>
8. 
9. // sumSequence - add a sequence of numbers entered from
10. //               the keyboard until the user enters a
11. //               negative number.
12. //               return - the summation of numbers entered
13. int sumSequence()
14. {
15.     // loop forever
16.     int nAccumulator = 0;
17. 	for(;;)
18. 	{
19.         // fetch another number
20. 	    int nValue = 0;
21. 	    cout << "Enter next number: ";
22. 	    cin  >> nValue;
23. 
24.         // if it's negative...
25. 	    if (nValue < 0)
26. 	    {
27.             // ...then exit from the loop
28. 		    break;
29.         }
30. 
31.         // ...otherwise add the number to the
32.         // accumulator
33.         nAccumulator = nAccumulator + nValue;
34. 	}
35. 
36.     // return the accumulated value
37.     return nAccumulator;
38. }
39. 
40. int main(int nArg, char* nArgs[])
41. {
42.     cout << "This program sums multiple series\n"
43.          << "of numbers. Terminate each sequence\n"
44.          << "by entering a negative number.\n"
45.          << "Terminate the series by entering two\n"
46.          << "negative numbers in a row\n";
47. 
48.     // Continue to accumulate numbers...
49.     int nAccumulatedValue;
50.     do
51.     {
52.         // sum a sequence of numbers entered from
53.         // the keyboard
54.         cout << "\nEnter next sequence\n";
55.         nAccumulatedValue = sumSequence();
56. 
57. 	    // now output the accumulated result
58. 	    cout << "\nThe total is " 
59.              << nAccumulatedValue 
60.              << "\n";
61. 
62.     // ...until the sum returned is 0
63.     } while (nAccumulatedValue != 0);
64.     cout << "Program terminating\n";
65.     return 0;
66. }
67.