The document discusses different types of loops in C++ including sentinel, while, do-while, and for loops. It provides the syntax for each loop type and examples of their usage. The while loop evaluates a test condition first before executing the loop body. The do-while loop is similar but evaluates the test condition at the end, so the body is always executed at least once. The for loop allows initializing a counter, evaluating a test condition, and updating the counter in each iteration. Nested for loops are demonstrated to output a triangle of asterisks of decreasing size.

1. Slide 1
Lecture
03

2. Slide 2
Loop Basics

3. Slide 3
Loop Types
 Sentinel
 while
 do-while
 Counting
 for

4. Slide 4
Sentinel Loops

5. Slide 5
while Syntax
while(test condition)
{
statement
}

6. Slide 6
When a program encounters a while loop, the test
condition is evaluated first. If the condition is TRUE,
the program executes the body of the loop. The
program then returns to the test condition and
reevaluates. If the condition is still TRUE, the body
executes again.
while Syntax

7. Slide 7
Example #1
while (7)
cout << “hello” << endl;

8. Slide 8
Example #2
#include<iostream>
using namespace std;
int main()
{
int input;
cout <<"enter number between 5 and 89, inclusive: ";
cin >> input;
while (input < 5 || input > 89)
{
cout << "that value is unacceptable... try again: ";
cin >> input;
}
cout << "the value"<<input<< "is in the interval[5, 89]"<< endl;
cin.get();
//system("PAUSE");
return 0;
}

9. Slide 9
Example #3
#include<iostream>
using namespace std;
int main()
{
long sum = 0;
int counter = 1;
while (counter<=100)
{
sum += counter;
counter++ ;
}
cout << "sum of first 100 integers is "<< sum ;
cin.get();
system("PAUSE");
return 0;
}

10. do-while Syntax
Do
{
statement
}
while (test condition);

11. Copyright © 2003 Pearson Education, Inc. Slide 11
The do-while loop is similar to the while loop, except
that the test condition occurs at the end of the loop.
The do-while loop is an exit-condition loop. This
means that the body of the loop is always executed
first. Then, the test condition is evaluated. If the test
condition is TRUE, the program executes the body of
the loop again. If the test condition is FALSE, the loop
terminates and program execution continues with the
statement following the while.
do-while Syntax

12. Slide 12
Example #1
do{
cout << "Enter an integer between 2 and 174 (inclusive)"
<< "that is a multiple of 3: ";
cin >> input;
}
while (!(input >= 2 && input <= 174 && input%3 == 0));

13. Slide 13
Counting Loops

14. Slide 14
for Syntax
for (startExpression; testExpression; countExpression)
}
statement
}

15. Slide 15
• The startExpression is evaluated before the loop begins. It is
acceptable to declare and assign in the startExpression(such as int x =
1;).
• This startExpression is evaluated only once at the beginning of the loop.
• The testExpression will evaluate to TRUE (nonzero) or FALSE (zero).
While TRUE, the body of the loop repeats. When the testExpression
becomes FALSE, the looping stops and the program continues with the
statement immediately following the for loop body in the program code.
• The countExpression executes after each trip through the loop. The
count may increase/decrease by an increment of 1 or of some other
value.
• Braces are not required if the body of the for loop consists of only ONE
statement. Please indent the body of the loop for readability.
for Syntax

16. Slide 16
Example #1
int max;
float average;
long sum = 0;
short i = 0;
cout << "enter positive integer: ";
cin >> max;
for(i=0; i <= max; i++)
sum += i;
average = sum/max;
cout << "average is " << average << endl;

17. Slide 17
Goal Output
* * * * *
* * * *
* * *
* *
*
Example #2

18. Slide 18
Outputting 5 Lines
for (int i = 1; i <= 5; i++)
{
cout << endl;
}

19. Slide 19
Outputting 5 Stars
for (int i = 1; i <= 5; i++)
{
cout << “* ”;
}

20. Slide 20
Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
output
i=1
j=?
variable values

21. Slide 21
Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
output
i=1
j=?
variable values

22. Slide 22
Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
output
i=1
j=1
variable values

23. Slide 23
Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
*
output
i=1
j=1
variable values

24. Slide 24
Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
*
output
i=1
j=2
variable values

25. Slide 25
Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
* *
output
i=1
j=2
variable values

26. Slide 26
Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
* *
output
i=1
j=3
variable values

27. Slide 27
Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
* * *
output
i=1
j=3
variable values

28. Slide 28
Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
* * *
output
i=1
j=4
variable values

29. Slide 29
Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
* * * *
output
i=1
j=4
variable values

30. Slide 30
Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
* * * *
output
i=1
j=5
variable values

31. Slide 31
Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
* * * * *
output
i=1
j=5
variable values

32. Slide 32
Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
* * * * *
output
i=1
j=6
variable values

33. Slide 33
Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
* * * * *
output
i=1
j=6
variable values

34. Slide 34
Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
* * * * *
output
i=2
j=?
variable values

35. Slide 35
Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
* * * * *
output
i=2
j=1
variable values

36. Slide 36
Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
* * * * *
*
output
i=2
j=1
variable values

37. Slide 37
Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
* * * * *
*
output
i=2
j=2
variable values

38. Slide 38
Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
* * * * *
* *
output
i=2
j=2
variable values

39. Slide 39
Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
* * * * *
* *
output
i=2
j=3
variable values

40. Slide 40
Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * *
output
i=2
j=3
variable values

41. Slide 41
Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * *
output
i=2
j=4
variable values

42. Slide 42
Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
output
i=2
j=4
variable values

43. Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
output
i=2
j=5
variable values

44. Slide 44
Combining
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * * *
output
i=2
j=5
variable values
oops!!!

45. Slide 45
Goal vs Actual
Goal
* * * * *
* * * *
* * *
* *
*
Actual
* * * * *
* * * * *
* * * * *
* * * * *
* * * * *
j=1
j=2
j=3
j=4
j=5
i=1
i=2
i=3
i=4
i=5

46. Slide 46
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
output
i=1
j=?
variable values

47. Slide 47
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
output
i=1
j=1
variable values

48. Slide 48
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
*
output
i=1
j=1
variable values

49. Slide 49
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
*
output
i=1
j=2
variable values

50. Slide 50
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* *
output
i=1
j=2
variable values

51. Slide 51
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* *
output
i=1
j=3
variable values

52. Slide 52
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * *
output
i=1
j=3
variable values

53. Slide 53
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * *
output
i=1
j=4
variable values

54. Slide 54
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * *
output
i=1
j=4
variable values

55. Slide 55
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
output
i=1
j=5
variable values

56. Slide 56
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
output
i=1
j=6
variable values

57. Slide 57
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
output
i=1
j=6
variable values

58. Slide 58
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
output
i=2
j=?
variable values

59. Slide 59
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
output
i=2
j=1
variable values

60. Slide 60
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
*
output
i=2
j=1
variable values

61. Slide 61
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
*
output
i=2
j=2
variable values

62. Slide 62
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* *
output
i=2
j=2
variable values

63. Slide 63
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* *
output
i=2
j=3
variable values

64. Slide 64
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * *
output
i=2
j=3
variable values

65. Slide 65
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * *
output
i=2
j=4
variable values

66. Slide 66
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
output
i=2
j=4
variable values

67. Slide 67
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
output
i=2
j=5
variable values

68. Slide 68
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
output
i=2
j=5
variable values

69. Slide 69
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
output
i=3
j=?
variable values

70. Slide 70
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
output
i=3
j=1
variable values

71. Slide 71
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
*
output
i=3
j=1
variable values

72. Slide 72
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
*
output
i=3
j=2
variable values

73. Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
* *
output
i=3
j=2
variable values

74. Slide 74
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
* *
output
i=3
j=3
variable values

75. Slide 75
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
* * *
output
i=3
j=3
variable values

76. Slide 76
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
* * *
output
i=3
j=4
variable values

77. Slide 77
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
* * *
output
i=3
j=4
variable values

78. Slide 78
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
* * *
output
i=4
j=?
variable values

79. Slide 79
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
* * *
output
i=4
j=1
variable values

80. Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
* * *
*
output
i=4
j=1
variable values

81. Slide 81
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
* * *
*
output
i=4
j=2
variable values

82. Slide 82
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
* * *
* *
output
i=4
j=2
variable values

83. Slide 83
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
* * *
* *
output
i=4
j=3
variable values

84. Slide 84
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
* * *
* *
output
i=4
j=3
variable values

85. Slide 85
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
* * *
* *
output
i=5
j=?
variable values

86. Slide 86
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
* * *
* *
output
i=5
j=1
variable values

87. Slide 87
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
* * *
* *
*
output
i=5
j=1
variable values

88. Slide 88
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
* * *
* *
*
output
i=5
j=2
variable values

89. Slide 89
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
* * *
* *
*
output
i=5
j=2
variable values

90. Slide 90
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
* * *
* *
*
output
i=6
j=?
variable values

91. Slide 91
Fixed
for (int i=1; i <= 5; i++)
{
for (int j=1; j <= 5 – i + 1; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
* * *
* *
*
output
i=6
j=?
variable values

92. Slide 92
* * * * *
* * * *
* * *
* *
*

93. Slide 93
Solution Rows
for (short i = 0; i < 5; i++)
{
for (short j = 1; j <= i; j++)
cout << " ";
for (short j = i; j < 5; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
* * *
* *
*

94. Slide 94
Solution Spaces
for (short i = 0; i < 5; i++)
{
for (short j = 1; j <= i; j++)
cout << " ";
for (short j = i; j < 5; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
* * *
* *
*

95. Slide 95
Solution Stars
for (short i = 0; i < 5; i++)
{
for (short j = 1; j <= i; j++)
cout << " ";
for (short j = i; j < 5; j++)
cout << "* ";
cout << endl;
}
* * * * *
* * * *
* * *
* *
*

96. Slide 96
Random Number Generation

97. Slide 97
rand()
#include <iostream>
using namespace std;
int main()
{
for(int i = 1; i <= 10; i++)
cout << rand() << endl;
return 0;
}

98. Slide 98
rand()
#include <iostream>
using namespace std;
int main()
{
for(int i = 1; i <= 10; i++)
cout << rand() << endl;
return 0;
}
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First Execution

99. Slide 99
rand()
#include <iostream>
using namespace std;
int main()
{
for(int i = 1; i <= 10; i++)
cout << rand() << endl;
return 0;
}
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First Execution
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Second Executio

100. Slide 100
Pseudo-Random Generation
The numbers aren't actually random -- they're generated by a formula,
so they're just pseudorandom.

101. Slide 101
The pseudo-random number generator is initialized using the argument
passed as seed.
For every different seed value used in a call to srandsrand, the pseudo-randompseudo-random
number generatornumber generator can be expected to generate a different succession of
results in the subsequent calls to rand.
Two different initializations with the same seed will generate the same
succession of results in subsequent calls to rand.
In order to generate random-like numbers, srandsrand is usually initialized to some
distinctive runtime value, like the value returned by function time (declared in
header <ctime><ctime>). This is distinctive enough for most trivial randomization
needs.

102. Slide 102
srand()
#include <iostream>
#include <ctime>
#include <cstdlib>
using namespace std;
int main()
{
srand(time(NULL));
for(int i = 1; i <= 10; i++)
cout << rand() << endl;
return 0;
}

103. Slide 103
srand()
#include <iostream>
#include <ctime>
#include <cstdlib>
using namespace std;
int main()
{
srand(time(NULL));
for(int i = 1; i <= 10; i++)
cout << rand() << endl;
return 0;
}
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First Execution

104. Slide 104
srand()
#include <iostream>
#include <ctime>
#include <cstdlib>
using namespace std;
int main()
{
srand(time(NULL));
for(int i = 1; i <= 10; i++)
cout << rand() << endl;
return 0;
}
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First Execution
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Second Execution

105. Slide 105
limiting range: [0, MAX_RAND]
#include <iostream>
#include <ctime>
#include <cstdlib>
using namespace std;
int main()
{
long next_value;
srand(time(NULL));
for (int i = 1; i <= 100000; i++)
if (rand()%100 <= 34)
cout << "hello" << endl; // ~35,000 times
else
cout << "goodbye" << endl; // ~65,000 times
return 0;
}

106. Slide 106
#include <iostream>
using namespace std;
void main ()
{
int x, y;
double z;
if(typeid(x) == typeid(y))
cout << "x and y are of same type."<<endl;
else
cout<< "x and y are of different type. " <<endl;
cout << "The type of z is "<< typeid(z).name()<<endl;
cout<< "The type of y is "<< typeid(y).name() << endl;
}
typeid ()
The expected output of the program is given below.
x and y are of same type.
The type of z is double
The type of y is int
The operator typeid () identifies the type of variable. Here we only show the use
of the operator. It returns reference to type of its argument. It is coded as:
typeid(object);

107. Slide 107