1. C++ Iterative Constructs
Three constructs
while statement
for statement
do-while statement

2. While Syntax

3. While Semantics

4. Computing an Average int listSize = 4; int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;

5. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;

6. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;

7. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
sum

8. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
sum

9. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
sum
value --

10. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
sum
value 1

11. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
sum 1
value 1

12. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed 1
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
sum 1
value 1

13. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed 1
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
sum 1
value 1

14. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed 1
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
sum 1
value --

15. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed 1
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
sum 1
value 5

16. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed 1
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
sum 6 1
value 5

17. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed 2 1
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
sum 6
value 5

18. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed 2
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
sum 6 6
value 5

19. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed 2 2
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
sum 6
value --

20. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed 2 2
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
sum 6
value 3

21. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed 2
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
sum 9 6
value 3

22. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed 3 2
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
sum 9
value 3

23. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed 3 3
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
sum 9
value 3

24. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed 3 3
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
sum 9
value --

25. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed 3 3
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
sum 9
value 1

26. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed 3
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
sum 10 9
value 1

27. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed 4 3
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
sum 10
value 1

28. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed 4 3
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
sum 10
value 1

29. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed 4 3
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
sum 10
average
2.5

30. Execution Trace Suppose input contains: 1 5 3 1 6 listSize 4
numberProcessed 4 3
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
sum 10
average
2.5

31. Stays in stream until extracted
Suppose input contains:
Execution Trace
Stays in stream until extracted
int listSize = 4;
int numberProcessed = 0;
double sum = 0;
while (numberProcessed < listSize) {
double value;
cin >> value;
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;

32. Power of Two Table const int TableSize = 20; int i = 0;
long Entry = 1;
cout << "i" << "\t\t" << "2 ** i" << endl;
while (i < TableSize) { cout << i << "\t\t" << Entry << endl; Entry = 2 * Entry; ++i; }

33. Better Way of Averaging
The value of the input operation corresponds to true only if a successful extraction was made
int numberProcessed = 0;
double sum = 0;
double value;
while ( cin >> value ) {
sum += value;
++numberProcessed; }
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
What if list is empty?

34. Even Better Way of Averaging
int numberProcessed = 0;
double sum = 0;
double value;
while ( cin >> value ) {
sum += value;
++numberProcessed; }
if ( numberProcessed > 0 ) {
double average = sum / numberProcessed ;
cout << "Average: " << average << endl;
else {
cout << "No list to average" << endl;

35. The For Statement Syntax for (ForInit ; ForExpression; PostExpression)
Action
Example
for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; }

37. Execution Trace i
for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; }
cout << "all done" << endl;

38. Execution Trace i
for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; }
cout << "all done" << endl;

39. Execution Trace i
for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; }
cout << "all done" << endl;
i is 0

40. Execution Trace i
for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; }
cout << "all done" << endl;
i is 0

41. Execution Trace i 1
for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; }
cout << "all done" << endl;
i is 0

42. Execution Trace i 1
for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; }
cout << "all done" << endl;

43. Execution Trace i 1
for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; }
cout << "all done" << endl;
i is 0
i is 1

44. Execution Trace i 1
for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; }
cout << "all done" << endl;
i is 0
i is 1

45. Execution Trace i 2
for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; }
cout << "all done" << endl;
i is 0
i is 1

46. Execution Trace i 2
for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; }
cout << "all done" << endl;
i is 0
i is 1

47. Execution Trace i 2
for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; }
cout << "all done" << endl;
i is 0
i is 1
i is 2

48. Execution Trace i 2
for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; }
cout << "all done" << endl;
i is 0
i is 1
i is 2

49. Execution Trace i 3
for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; }
cout << "all done" << endl;
i is 0
i is 1
i is 2

50. Execution Trace i 3
for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; }
cout << "all done" << endl;
i is 0
i is 1
i is 2

51. Execution Trace i 3
for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; }
cout << "all done" << endl;
i is 0
i is 1
i is 2
all done

52. Table Revisiting const int TableSize = 20; long Entry = 1;
cout << "i" << "\t\t" << "2**i" << endl;
for (int i = 0; i <= TableSize; ++i) { cout << i << "\t\t" << Entry << endl; Entry *= 2; }

53. Table Revisiting const int TableSize = 20; long Entry = 1;
cout << "i" << "\t\t" << "2**i" << endl;
for (int i = 0; i < TableSize; ++i) { cout << i << "\t\t" << Entry << endl; Entry = 2 * Entry; }
cout << "i is" << i << endl; // illegal
The scope of i is limited to the loop!

54. int Counter1 = 0; int Counter2 = 0; int Counter3 = 0; int Counter4 = 0; int Counter5 = 0; ++Counter1;
for (int i = 1; i <= 10; ++i) { ++Counter2; for (int j = 1; j <= 20; ++j) { Counter3; }
++Counter4; }
++Counter5;
cout << Counter1 << " " << Counter2 << " "
<< Counter3 << " " << Counter4 << " "
<< Counter5 << endl;

55. For Into While Observation The for statement is equivalent to {
ForInit;
while (ForExpression) {
Action;
PostExpression; }