1. Intro to Programming Week # 4 Control Structure Lecture # 8
Department of Computer Science & Engineering
Air University
Intro to Programming Week # 4 Control Structure Lecture # 8
By: Saqib Rasheed

2. Increment operator ++
counter ++ ;
same as
counter = counter + 1;

3. Decrement operator --
counter -- ;
same as
counter = counter - 1

4. Post/Pre Increment Int x = 10 //Post Increment x++; cout<<x;
int y = 10;
cout<<y<<endl;
cout<<y++<<endl;
cout<<++y<<endl;
cout<<y--<<endl;
cout<<--y<<endl; 10 12

5. Post/Pre Increment int y = 10; int y = 5, x = 6; y--; y--;
cout<<y<<endl;
cout<<y--<<endl;
cout<<++y<<endl;
cout<<y<<endl
int y = 5, x = 6;
y--;
cout<<y<<endl;
cout<<y-- + x++<<endl;
cout<<++y + --x<<endl;
cout<<y + x<<endl;
cout<<"y = "<<y <<endl;
cout<<"x = "<<x <<endl; 4 10
Y = 4
X = 6 9

6. Compound Assignment Operators Operator =

7. +=
counter += 3 ;
same as
counter = counter + 3 ;

8. -=
counter -= 5 ;
same as
counter = counter – 5 ;

9. *=
x*=2
x = x * 2

10. /=
x /= 2
x = x / 2

11. %=
x %= 2 ;
same as
x = x % 2 ;

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

13. Why we use loops Add these Numbers 1+2+3+4+5+6+7+8+9= 55 Add these
………… = ?

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

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

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

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

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

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

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

22. 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

23. 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

24. 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

25. 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

26. 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

27. 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

28. 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

29. 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

30. 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

31. Sum of 10 int x=0; for (int i =0; i<=10; i++) { x = x+i; }
cout<<x<<endl;

32. While Syntax

33. While Semantics

34. Example
int sum , number ; sum = 0 ; number = 1 ; while ( number <= 1000 ) { sum = sum + number ; number = number + 1 ; } cout << “ The sum of the first 1000 integer starting from 1 is ” << sum ;

35. (User Defined) while (number <= UpperLimit)

36. Example
int sum, number , UpperLimit ; sum = 0 ; number = 1 ; cout << “ Please enter the upper limit for which you want the sum ” ; cin >> UpperLimi t; while (number <= UpperLimit) { sum = sum + number ; number = number +1 ; } cout << “ The sum of the first ” << UpperLimit << “ integer is ” << sum ;

37. Sum Of Even Numbers
if ( number % 2 == 0 ) { sum = sum + number ; } number = number + 1 ;

38. Example
sum = 0; number = 1; cout << “ Please enter the upper limit for which you want the sum ”; cin >> UpperLimit; while (number <= UpperLimit) { if (number % 2 == 0) sum = sum + number; number = number + 1; } cout << “ The sum of all even integer between 1 and ” << UpperLimit << “ is” << sum;

39. 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;

40. 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;

41. 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;

42. 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

43. 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

44. 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 --

45. 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

46. 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

47. 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

48. 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

49. 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 --

50. 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

51. 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

52. 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

53. 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

54. 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 --

55. 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

56. 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

57. 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

58. 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

59. 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 --

60. 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

61. 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

62. 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

63. 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

64. 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

65. 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

66. 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;

67. Table of Two 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; }

68. 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?

69. 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;

70. 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; }

71. 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!

72. Out Put?
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;

73. Only extracts nonblank characters
Counting Characters
int NumberOfNonBlanks = 0;
int NumberOfUpperCase = 0;
char c;
while (cin >> c) {
++NumberOfNonBlanks;
if ((c >= 'A') && (c <= 'Z')) { ++NumberOfUpperCase; }
cout << "Nonblank characters: " << NumberOfNonBlanks
<< endl << "Uppercase characters: "
<< NumberOfUpperCase << endl;
Only extracts nonblank characters

74. Counting Characters int NumberOfNonBlanks = 0;
int NumberOfUpperCase = 0;
char c;
cout<<“To Terminate Press 0 ”;
while (cin >> c && C !- ‘0’) {
++NumberOfNonBlanks;
if ((c >= 'A') && (c <= 'Z')) { ++NumberOfUpperCase; }
cout << "Nonblank characters: " << NumberOfNonBlanks
<< endl << "Uppercase characters: "
<< NumberOfUpperCase << endl;
Use to
terminate

75. Counting All Characters
char c;
int NumberOfCharacters = 0;
int NumberOfLines = 0;
while (cin.get(c) && c !='0') { ++NumberOfCharacters; if (c == '\n') { ++NumberOfLines } }
cout << "Characters: " << NumberOfCharacters
<< endl << "Lines: " << NumberOfLines
<< endl;
Extracts all characters

76. File Processing #include <iostream> #include <fstream>
using namespace std;
int main() {
ifstream fin("mydata.txt");
int ValuesProcessed = 0;
float ValueSum = 0;
float Value;
while ( fin >> Value ) {
ValueSum += Value;
++ValuesProcessed; }
if (ValuesProcessed > 0) {
ofstream fout("average.txt");
float Average = ValueSum / ValuesProcessed;
fout << "Average: " << Average << endl;
return 0;
else {
cerr << "No list to average" << endl;
return 1;

77. Iteration Do’s Key Points
Make sure there is a statement that will eventually terminate the iteration criterion
The loop must stop!
Make sure that initialization of loop counters or iterators is properly performed
Have a clear purpose for the loop
Document the purpose of the loop
Document how the body of the loop advances the purpose of the loop