1. Computer Science 1620
Loops

2. Write a program to display a table of squares and cubes of the first 5 integers:
NUMBER SQUARE CUBE

3. Write a program to display a table of squares and cubes of the first 5 integers:
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl;
num++;
return 0; }

5. Write a program to display a table of squares and cubes of the first 5 integers:
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl;
num++;
return 0; }

6. Write a program to display a table of squares and cubes of the first 20 integers:
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl;
num++;
return 0; }

7. Write a program to display a table of squares and cubes of the first 50 integers:
#include <iostream>
using namespace std;
#include <iomanip>
int main ()
cout << " " << endl;
cout << "NUMBER SQUARE CUBE" << endl; {
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl;
int num = 1;
num++;
return 0; }

8. Write a program to display a table of squares and cubes of the first n integers, where n is specified by the user (let n be of max 10):
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
int num = 0;
int size;
cout << "Please enter the number of squares and cubes to display: ";
cin >> size;
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
if (num < size) {
num++;
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl; }

9. Write a program to display a table of squares and cubes of the first n integers, where n is specified by the user (let n be of max 10):
if (num < size) {
num++;
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl; }
return 0;

10. Issues
1) Repeated code
2) Non-scalable
3) Non user-friendly

11. While Loop while: while ( ) boolean expression C++ Statement
this statement will be executed repeatedly, for as long as this expression has value true
note that the statement can be a compound statement

12. Rewrite our program to display a table of squares and cubes of the first 5 integers:
NUMBER SQUARE CUBE

13. Write a program to display a table of squares and cubes of the first 5 integers:
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl;
num++;
return 0; }

14. Write a program to display a table of squares and cubes of the first 5 integers:
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl;
num++; }
return 0;

15. Program: Program Memory: Output: #include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
num++; }
return 0;
Output:

16. Program: Program Memory: Output:
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
num++; }
return 0;
cout << "NUMBER SQUARE CUBE" << endl;
Output:
NUMBER SQUARE CUBE

17. Program: Program Memory: Output:
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
num++; }
return 0;
cout << " " << endl;
Output:
NUMBER SQUARE CUBE

18. Program: Program Memory: num 1 Output: int num = 1;
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
num++; }
return 0;
num 1
int num = 1;
Output:
NUMBER SQUARE CUBE

19. Program: Program Memory: num 1
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
num++; }
return 0;
num 1
while (num <= 5) {
Since 1 <= 5, the expression is true, so the while statement is executed
Output:
NUMBER SQUARE CUBE

20. Program: Program Memory: num 1 Output: #include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
num++; }
return 0;
num 1
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
Output:
NUMBER SQUARE CUBE

21. We are now at the end of the while statement.
Program:
Program Memory:
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
num++; }
return 0;
num 2 1
num++;
Output:
We are now at the end of the while statement.
We "loop" to the beginning again, testing to see if the expression is false.
NUMBER SQUARE CUBE

22. Program: Program Memory: num 2
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
num++; }
return 0;
num 2
while (num <= 5) {
Since 2 <= 5, the expression is true, so the while statement is executed
Output:
NUMBER SQUARE CUBE

23. Program: Program Memory: num 2 Output: #include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
num++; }
return 0;
num 2
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
Output:
NUMBER SQUARE CUBE

24. We are now at the end of the while statement.
Program:
Program Memory:
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
num++; }
return 0;
num 2 3
num++;
Output:
We are now at the end of the while statement.
We "loop" to the beginning again, testing to see if the expression is false.
NUMBER SQUARE CUBE

25. Program: Program Memory: num 3
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
num++; }
return 0;
num 3
while (num <= 5) {
Since 3 <= 5, the expression is true, so the while statement is executed
Output:
NUMBER SQUARE CUBE

26. Program: Program Memory: num 3 Output: #include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
num++; }
return 0;
num 3
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
Output:
NUMBER SQUARE CUBE

27. We are now at the end of the while statement.
Program:
Program Memory:
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
num++; }
return 0;
num 3 4
num++;
Output:
We are now at the end of the while statement.
We "loop" to the beginning again, testing to see if the expression is false.
NUMBER SQUARE CUBE

28. Program: Program Memory: num 4
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
num++; }
return 0;
num 4
while (num <= 5) {
Since 4 <= 5, the expression is true, so the while statement is executed
Output:
NUMBER SQUARE CUBE

29. Program: Program Memory: num 4 Output: #include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
num++; }
return 0;
num 4
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
Output:
NUMBER SQUARE CUBE

30. We are now at the end of the while statement.
Program:
Program Memory:
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
num++; }
return 0;
num 5 4
num++;
Output:
We are now at the end of the while statement.
We "loop" to the beginning again, testing to see if the expression is false.
NUMBER SQUARE CUBE

31. Program: Program Memory: num 5
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
num++; }
return 0;
num 5
while (num <= 5) {
Since 5 <= 5, the expression is true, so the while statement is executed
Output:
NUMBER SQUARE CUBE

32. Program: Program Memory: num 5 Output: #include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
num++; }
return 0;
num 5
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
Output:
NUMBER SQUARE CUBE

33. We are now at the end of the while statement.
Program:
Program Memory:
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
num++; }
return 0;
num 6 5
num++;
Output:
We are now at the end of the while statement.
We "loop" to the beginning again, testing to see if the expression is false.
NUMBER SQUARE CUBE

34. Program: Program Memory: num 6
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
num++; }
return 0;
num 6
while (num <= 5) {
Since 6 <= 5 is false, the while loop statement is not executed, but skipped (just like with an if)
Output:
NUMBER SQUARE CUBE

35. Program: Program Memory: num 6 Output: return 0;
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10)
<< num*num << setw(8) << num*num*num << endl;
num++; }
return 0;
num 6
return 0;
Output:
NUMBER SQUARE CUBE

37. Modify the program to print out the results for the first 20 integers:
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl;
num++; }
return 0;

38. Modify the program to print out the results for the first 20 integers:
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 20) {
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl;
num++; }
return 0;

39. Modify the program to print out the results for the first 10000 integers:
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 10000) {
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl;
num++; }
return 0;

40. Modify the program to print out the results for the first 10000 integers:
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 10000) {
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl;
num++; }
return 0;

41. Modify the program to print out the results for the first n integers, where n is specified by the user:
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 10000) {
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl;
num++; }
return 0;

42. Modify the program to print out the results for the first n integers, where n is specified by the user:
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
int n;
cout << "Please enter the number of squares and cubes to display: ";
cin >> n;
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 10000) {
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl;
num++; }
return 0;

43. Modify the program to print out the results for the first n integers, where n is specified by the user:
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
int n;
cout << "Please enter the number of squares and cubes to display: ";
cin >> n;
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= n) {
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl;
num++; }
return 0;

44. Designing the While Loop
typical format:
Loops are typically controlled by a variable (or set of variables). This is where the variables receive their values.
initialization
while ( ) { }
boolean expression
C++ Statements
This is typically where the control variables are updated.
<update>

45. Modify the program to print out the results for the first 5 integers:
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl;
num++; }
return 0;
Initialization
Update

46. Loop Programming useful to determine beforehand
what the initialization value of the control variable is:
assigning a variable a value
reading a value from the user
what the loop expression is
what the loop statement will do (aside from the update)
what the update is

47. Example: Write a program that calculates the sum of the first 20 positive integers ( …. + 20)
Initialization:
initialize control variable to 1
initialize the sum to 0
Loop Expression
Loop while the control variable <= 20
Loop statement
Add the control variable value to the current sum
Update
increment the variable by 1

48. Write a program that calculates the sum of the first 20 positive integers.
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
int sum = 0;
int num = 1;
while (num <= 20) {
sum += num;
num++; }
cout << "Sum = " << sum << endl;
return 0;
initialization
while (
boolean expression)
Initialization:
initialize control variable to 1
initialize sum to 0
Loop Expression
Loop while the control variable <= 20
Loop statement
Add the control variable value to the current sum
Update
increment the variable by 1
C++ Statements
<update> }

49. Write a program that calculates the sum of the first 20 positive integers.
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
int sum = 0;
int num = 1;
while (num <= 20) {
sum += num;
num++; }
cout << "Sum = " << sum << endl;
return 0;
while (
boolean expression)
Initialization:
initialize control variable to 1
initialize sum to 0
Loop Expression
Loop while the control variable <= 20
Loop statement
Add the control variable value to the current sum
Update
increment the variable by 1
C++ Statements
<update> }

50. Write a program that calculates the sum of the first 20 positive integers.
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
int sum = 0;
int num = 1;
while (num <= 20) {
sum += num;
num++; }
cout << "Sum = " << sum << endl;
return 0;
while (
Initialization:
initialize control variable to 1
initialize sum to 0
Loop Expression
Loop while the control variable <= 20
Loop statement
Add the control variable value to the current sum
Update
increment the variable by 1
C++ Statements
<update> }

51. Write a program that calculates the sum of the first 20 positive integers.
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
int sum = 0;
int num = 1;
while (num <= 20) {
sum += num;
num++; }
cout << "Sum = " << sum << endl;
return 0;
while (
Initialization:
initialize control variable to 1
initialize sum to 0
Loop Expression
Loop while the control variable <= 20
Loop statement
Add the control variable value to the current sum
Update
increment the variable by 1
<update> }

52. Write a program that calculates the sum of the first 20 positive integers.
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
int sum = 0;
int num = 1;
while (num <= 20) {
sum += num;
num++; }
cout << "Sum = " << sum << endl;
return 0;
Initialization:
initialize control variable to 1
initialize sum to 0
Loop Expression
Loop while the control variable <= 20
Loop statement
Add the control variable value to the current sum
Update
increment the variable by 1

53. Write a program that calculates the sum of the first 20 positive integers.
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
int sum = 0;
int num = 1;
while (num <= 20) {
sum += num;
num++; }
cout << "Sum = " << sum << endl;
return 0;
Initialization:
initialize control variable to 1
initialize sum to 0
Loop Expression
Loop while the control variable <= 20
Loop statement
Add the control variable value to the current sum
Update
increment the variable by 1

55. There are several forms of loops
counter-controlled loops
when you know exactly how many iterations there will be (like the previous example)
sentinel-controlled loops
when you don't know how many iterations there will be
require a special value for stopping
flag-controlled loop
loops until a boolean variable changes value

56. Sentinel-controlled Loop
common when reading input
from a user
from a file
continues to loop until a pre-defined special value is input
value is called a sentinel

57. Example: Write a program to read in numbers from a user, and prints the sum of the numbers.
How do we know when the user is done?
Solution: Use a sentinal value (such as 0)
That is, loop until the user enters the sentinel value, then stop and print the sum of the numbers.

58. Example: Write a program to read in numbers from a user, and prints the sum of the numbers.
Initialization:
initialize sum to 0
read input from user into control variable
Loop Expression
Loop while the control variable is not zero
Loop statement
Add the control variable value to the current sum
Update

59. Write a program to read in numbers from a user, and prints the sum of the numbers.
#include <iostream>
using namespace std;
int main () {
int sum = 0;
int num;
cout << "Please enter a number: ";
cin >> num;
while (num != 0) {
sum += num; }
cout << "Sum = " << sum << endl;
return 0;
initialization
Initialization:
initialize sum to 0
read input from user into control variable
Loop Expression
Loop while the control variable is not zero
Loop statement
Add the control variable value to the current sum
Update
while (
boolean expression)
C++ Statements
<update> }

60. Write a program to read in numbers from a user, and prints the sum of the numbers.
#include <iostream>
using namespace std;
int main () {
int sum = 0;
int num;
cout << "Please enter a number: ";
cin >> num;
while (num != 0) {
sum += num; }
cout << "Sum = " << sum << endl;
return 0;
Initialization:
initialize sum to 0
read input from user into control variable
Loop Expression
Loop while the control variable is not zero
Loop statement
Add the control variable value to the current sum
Update
while (
boolean expression)
C++ Statements
<update> }

61. Write a program to read in numbers from a user, and prints the sum of the numbers.
#include <iostream>
using namespace std;
int main () {
int sum = 0;
int num;
cout << "Please enter a number: ";
cin >> num;
while (num != 0) {
sum += num; }
cout << "Sum = " << sum << endl;
return 0;
Initialization:
initialize sum to 0
read input from user into control variable
Loop Expression
Loop while the control variable is not zero
Loop statement
Add the control variable value to the current sum
Update
C++ Statements
<update> }

62. Write a program to read in numbers from a user, and prints the sum of the numbers.
#include <iostream>
using namespace std;
int main () {
int sum = 0;
int num;
cout << "Please enter a number: ";
cin >> num;
while (num != 0) {
sum += num; }
cout << "Sum = " << sum << endl;
return 0;
Initialization:
initialize sum to 0
read input from user into control variable
Loop Expression
Loop while the control variable is not zero
Loop statement
Add the control variable value to the current sum
Update
<update> }

63. Write a program to read in numbers from a user, and prints the sum of the numbers.
#include <iostream>
using namespace std;
int main () {
int sum = 0;
int num;
cout << "Please enter a number: ";
cin >> num;
while (num != 0) {
sum += num; }
cout << "Sum = " << sum << endl;
return 0;
Initialization:
initialize sum to 0
read input from user into control variable
Loop Expression
Loop while the control variable is not zero
Loop statement
Add the control variable value to the current sum
Update }

64. Write a program to read in numbers from a user, and prints the sum of the numbers.
#include <iostream>
using namespace std;
int main () {
int sum = 0;
int num;
cout << "Please enter a number: ";
cin >> num;
while (num != 0) {
sum += num; }
cout << "Sum = " << sum << endl;
return 0;
Initialization:
initialize sum to 0
read input from user into control variable
Loop Expression
Loop while the control variable is not zero
Loop statement
Add the control variable value to the current sum
Update }

66. For Loop similar to while loop
explicit place for initialization and update
each component separated by semicolons
initialization
while ( ) { }
boolean expression
C++ Statements
update
for ( ; ; )
initialization
boolean expression
update
C++ Statements

67. For Loop this statement is executed once, before the loop starts
this expression is evaluated before the loop statement
this statement is executed after the loop statement
for ( ; ; )
initialization
boolean expression
update
C++ Statements

68. Rewrite our while loop for the square and cube table using a for loop
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl;
num++; }
for ( ; ; )
initialization
boolean expression
update
C++ Statements

69. Rewrite our while loop for the square and cube table using a for loop
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl;
num++; }
for ( ; ; )
int num = 1
boolean expression
update
C++ Statements

70. Rewrite our while loop for the square and cube table using a for loop
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl;
num++; }
for ( ; ; )
int num = 1
num <=5
update
C++ Statements

71. Rewrite our while loop for the square and cube table using a for loop
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl;
num++; }
for ( ; ; )
int num = 1
num <=5
num++
C++ Statements

72. Rewrite our while loop for the square and cube table using a for loop
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl;
num++; }
for ( ; ; )
int num = 1
num <=5
num++
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl;

73. Rewrite our while loop for the square and cube table using a for loop
int num = 1;
while (num <= 5) {
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl;
num++; }
for (int num = 1; num <= 5; num++)
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl;

74. Write a program to display a table of squares and cubes of the first 5 integers:
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << "NUMBER SQUARE CUBE" << endl;
cout << " " << endl;
for (int num = 1; num <= 5; num++)
cout << setw(6) << num << setw(10) << num*num << setw(8) << num*num*num << endl;
return 0; }

75. For Loops
you can have more than one statement (actually expressions!!) in the initialization component
separated by commas (comma operator)
int x, sum;
for (x = 1, sum = 0; x < 20; x++)
sum += x;

76. Comma operator (left to right, very low precedence!)
expr1 , expr2
(expr1 is evaluated, expr2 is evaluated, result is the value of expr2)
Examples
2,3,4,5 evaluates to 5
Was created for “for” loop!

77. For Loops you can declare a variable in the initialization component
int sum = 0;
for (int x = 1; x < 20; x++)
sum += x;

78. For Loops
you can declare more than one variable of the same type in the initialization statement
they must be declared with only one keyword
// this is ok
for (int x = 1, sum = 0; x < 20; x++)
sum += x;
// this is not ok
for (int x = 1, int sum = 0; x < 20; x++)
sum += x;

79. For Loops
you cannot declare variables of different types in the initialization component
you can, however, assign variables of different types in the initialization component
// this is not ok
for (int x = 1, double sum = 0; x < 20; x++)
sum += x;
int x;
double sum;
for (x = 1, sum = 0; x < 20; x++)
sum += x;

80. For Loops any while loop can be rewritten as a for loop how to choose?
Personal preference
For Loops are typically used when:
the initialization and update are simple (typically only one or two small statements)
the loop is count controlled (not sentinel controlled)

81. Example: Convert the following while loop to a for-loop
int sum = 0;
int num;
cout << "Please enter a number: ";
cin >> num;
while (num != 0) {
sum += num; }
Ugly – much easier to read as a while loop
int sum;
int num;
for (sum = 0; cout << "Please enter a number: ", cin >> num; num != 0; cout << "Please enter a number: ", cin >> num) {
sum += num; }

82. For Loops
it is not required that any code be placed into the initialization or update component
they can be empty
when they are empty, they are known as nulls
in this case, the for loop looks much like a while loop

83. Example: Convert the following while loop to a for-loop
int sum = 0;
int num;
cout << "Please enter a number: ";
cin >> num;
while (num != 0) {
sum += num; }
int sum = 0;
int num;
cout << "Please enter a number: ";
cin >> num;
for ( ; num != 0; ) {
sum += num; }

84. Question: How many times will the following loop execute?
Answer: 0 times
if the condition is initially false, the loop never executes
this means a while loop and a for loop may never execute their code
int max = 10;
int num = 11;
while (num < max) {
cout << num << endl;
num++; }

85. Do-While Syntax: do C++ Statement while ( ); boolean expression
The condition is tested after the statement is executed

86. Example: Write a program to read in numbers from a user, and prints the sum of the numbers.
User is done when 0 (sentinel) is typed in

87. Write a program to read in numbers from a user, and prints the sum of the numbers.
#include <iostream>
using namespace std;
int main () {
int sum = 0;
int num;
cout << "Please enter a number: ";
cin >> num;
while (num != 0) {
sum += num; }
cout << "Sum = " << sum << endl;
return 0; }

88. Write a program to read in numbers from a user, and prints the sum of the numbers.
#include <iostream>
using namespace std;
int main () {
int sum = 0;
int num;
cout << "Please enter a number: ";
cin >> num;
while (num != 0) {
sum += num; }
cout << "Sum = " << sum << endl;
return 0; }

89. Write a program to read in numbers from a user, and prints the sum of the numbers.
#include <iostream>
using namespace std;
int main () {
int sum = 0;
int num;
do {
cout << "Please enter a number: ";
cin >> num;
sum += num;
} while (num != 0);
cout << "Sum = " << sum << endl;
return 0; }
Since the code inside of the loop gets executed at least once, we can read our initial value inside the loop }

91. While/For vs. Do-While Which to use?
While/For Loops execute their statement 0 or more times
Do-while executes its statement at least 1 time
Which to use?
programmer preference
do-while loops are quite uncommon
more difficult to read
can be rewritten using a while loop

92. Example: Write a program that reads an integer n from the user and displays n stars in a line:
Enter the numbers of stars: 5
*****

93. Example: Write a program that reads an integer n from the user and displays n stars in a line:
#include <iostream>
using namespace std;
int main() {
int stars;
cout << "Enter the number of stars: ";
cin >> stars;
for (int i = 1; i <= stars; i++) {
cout << "*"; }
cout << endl;
return 0;

94. Example: Write a program that reads an integer n from the user and displays n stars in a line:
#include <iostream>
using namespace std;
int main() {
int n;
cout << "Enter the number of stars: ";
cin >> n;
for (int i = 1; i <= stars; i++) {
cout << "*"; }
cout << endl;
return 0;

95. Example: Write a program that reads an integer n from the user and displays n stars in a line:
#include <iostream>
using namespace std;
int main() {
int n;
cout << "Enter the number of stars: ";
cin >> n;
for (int i = 1; i <= n; i++) {
cout << "*"; }
cout << endl;
return 0;

96. Example: Write a program that reads an integer n from the user and displays n stars in a line:
#include <iostream>
using namespace std;
int main() {
int n;
cout << "Enter the number of stars: ";
cin >> n;
for (int i = 1; i <= n; i++) {
cout << "*"; }
cout << endl;
return 0;

97. Example: Write a program that reads an integer n from the user and displays n stars in a line:
#include <iostream>
using namespace std;
int main() {
int n;
cout << "Enter the number of stars: ";
cin >> n;
for (int i = 1; i <= n; i++) {
cout << "*"; }
cout << endl;
return 0;

98. Example: Write a program that reads an integer n from the user and displays n stars in a line:
#include <iostream>
using namespace std;
int main() {
int n;
cout << "Enter the number of stars: ";
cin >> n;
for (int i = 1; i <= n; i++) {
cout << "*"; }
cout << endl;
return 0;

99. Example: Write a program that reads an integer n from the user and displays n stars in a line:
#include <iostream>
using namespace std;
int main() {
int n;
cout << "Enter the number of stars: ";
cin >> n;
for (int i = 1; i <= n; i++) {
cout << "*"; }
cout << endl;
return 0;

100. Example: Write a program that reads an integer n from the user and displays n stars in a line:
#include <iostream>
using namespace std;
int main() {
int n;
cout << "Enter the number of stars: ";
cin >> n;
for (int i = 1; i <= n; i++) {
cout << "*"; }
cout << endl;
return 0;

101. Example: Write a program that reads an integer n from the user and displays n stars in a line:
#include <iostream>
using namespace std;
int main() {
int n;
cout << "Enter the number of stars: ";
cin >> n;
int i = 1;
while (i <= n) {
cout << "*";
i++; }
cout << endl;
return 0;

103. Nested Loops Nested Loops
recall that a loop body can contain virtually any C++ statement:
this includes another loop
when a loop is inside another loop, we call the inner loop a nested loop
the nested loop is called once for each iteration of the outer loop

104. Example: Write a program that reads an integer n from the user and displays a square of n x n stars:
Enter the height of square: 5
*****

105. Problem Breakdown: ***** for (int j = 0; j < n; j++) {
for (int i = 1; i <= stars; i++) {
cout << "*"; }
cout << endl;
Repeat n times
draw a line of n stars
go to next line

106. Problem Breakdown: ***** for (int j = 0; j < n; j++) {
for (int i = 1; i <= stars; i++) {
cout << "*"; }
cout << endl;
Repeat n times
Repeat n times
draw a line of n stars
go to next line

107. Problem Breakdown: ***** for (int j = 1; j <= n; j++) {
for (int i = 1; i <= stars; i++) {
cout << "*"; }
cout << endl;
Repeat n times
Repeat n times
draw a line of n stars
go to next line

108. Problem Breakdown: ***** for (int j = 1; j <= n; j++) {
for (int i = 1; i <= stars; i++) {
cout << "*"; }
cout << endl;
Repeat n times
Repeat n times
draw a line of n stars
go to next line
go to next line

109. Problem Breakdown: ***** for (int j = 1; j <= n; j++) {
for (int i = 1; i <= stars; i++) {
cout << "*"; }
cout << endl;
Repeat n times
Repeat n times
draw a line of n stars
go to next line
go to next line

110. Problem Breakdown: ***** ?? for (int j = 1; j <= n; j++) {
for (int i = 1; i <= stars; i++) {
cout << "*"; }
cout << endl;
Repeat n times
Repeat n times
draw a line of n stars
draw a line of n stars ??
go to next line
go to next line

111. This code drew us a line of n stars!!
Example: Write a program that reads an integer n from the user and displays n stars in a line:
#include <iostream>
using namespace std;
int main() {
int n;
cout << "Enter the number of stars: ";
cin >> n;
for (int i = 1; i <= n; i++) {
cout << "*"; }
cout << endl;
return 0;
for (int i = 1; i <= n; i++) {
cout << "*"; }
This code drew us a line of n stars!!

112. This code drew us a line of n stars!!
Example: Write a program that reads an integer n from the user and displays n stars in a line:
#include <iostream>
using namespace std;
int main() {
int n;
cout << "Enter the number of stars: ";
cin >> n;
for (int i = 1; i <= n; i++) {
cout << "*"; }
cout << endl;
return 0;
for (int i = 1; i <= n; i++) {
cout << "*"; }
This code drew us a line of n stars!!

113. Problem Breakdown: ***** ?? for (int j = 1; j <= n; j++) {
for (int i = 1; i <= stars; i++) {
cout << "*"; }
cout << endl;
Repeat n times
Repeat n times
for (int i = 1; i <= n; i++) {
cout << "*"; }
draw a line of n stars
draw a line of n stars ??
go to next line
go to next line

114. Problem Breakdown: ***** for (int j = 1; j <= n; j++) {
for (int i = 1; i <= n; i++) {
cout << "*"; }
cout << endl;
Repeat n times
draw a line of n stars
go to next line

115. Write a C++ program to display a square of stars on the screen:
#include <iostream>
using namespace std;
int main() {
int n;
cout << "Enter the height of the square: ";
cin >> n;
for (int j = 1; j <= n; j++) {
for (int i = 1; i <= n; i++) {
cout << "*"; }
cout << endl;
return 0;

117. Note that inside the inner loop, the code has access to the outer loop variables
for (int j = 1; j <= n; j++) {
for (int i = 1; i <= n; i++) {
cout << "*"; }
cout << endl;
At this point in the code,
we have access to i and
j variable

118. This means the outer loop can be used to control the inner loop
Example: Write a program to display the following to the screen: * **
***
****
*****
******
*******
********

119. Write a C++ program to display a square of stars on the screen:
#include <iostream>
using namespace std;
int main() {
int n;
cout << "Enter the height of the square: ";
cin >> n;
for (int j = 1; j <= n; j++) {
for (int i = 1; i <= n; i++) {
cout << "*"; }
cout << endl;
return 0;
What controls the length
of the line being drawn?

120. Problem Breakdown: * ** *** **** ***** ****** ******* ******** ??
for (int j = 1; j <= n; j++) {
for (int i = 1; i <= n; i++) {
cout << "*"; }
cout << endl;
Repeat n times
draw x stars, where x is the current pass through the loop. ??
go to next line

121. Problem Breakdown: * ** *** **** ***** ****** ******* ********
for (int j = 1; j <= n; j++) {
for (int i = 1; i <= j; i++) {
cout << "*"; }
cout << endl;
Repeat n times
draw x stars, where x is the current pass through the loop.
go to next line

122. Write a C++ program to display a triangle of stars on the screen:
#include <iostream>
using namespace std;
int main() {
int n;
cout << "Enter the height of the triangle: ";
cin >> n;
for (int j = 1; j <= n; j++) {
for (int i = 1; i <= j; i++) {
cout << "*"; }
cout << endl;
return 0;

123. It is possible to embed loops as deep as you like:
for (int a = 0; a < n; a++) {
for (int b = 0; b < n; b++) {
for (int c = 0; c < n; c++) {
for (int d = 0; d < n; d++) {
...

124. Caution must be used when embedding loops
Loops have the power to create a long program with few lines
Nested loops increase length multiplicatively
for (int i = 1; i <= n; i++) {
cout << "*"; }
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= n; j++) {
cout << "*"; }
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= j; j++) {
for (int k = 1; k <= j; k++) {
cout << "*"; }
cout statement
executes n times
cout statement
executes n2 times
cout statement
executes n3 times

125. break and continue C++ statements break continue terminates a loop
code begins at statement following loop
continue
skips the remaining code in the loop

126. Example: Write a program that reads in 5 user numbers, and displays their inverse (1/x)
if the user enters a 0, print "Stop trying to break my program", and exits the loop

127. #include <iostream> using namespace std; int main() { int x;
Write a program that reads in 5 user numbers, and displays their inverse (1/x)
if the user enters a 0, print "Stop trying to break my program", and exits the loop
#include <iostream>
using namespace std;
int main() {
int x;
for (int count = 0; count < 5; count++) {
cout << "Please enter a number: ";
cin >> x;
cout << "The inverse of " << x << " is " << (1.0 / x) << endl; }
return 0;

128. #include <iostream> using namespace std; int main() { int x;
Write a program that reads in 5 user numbers, and displays their inverse (1/x)
if the user enters a 0, print "Stop trying to break my program", and exits the loop
#include <iostream>
using namespace std;
int main() {
int x;
for (int count = 0; count < 5; count++) {
cout << "Please enter a number: ";
cin >> x;
cout << "The inverse of " << x << " is " << (1.0 / x) << endl; }
return 0;

130. #include <iostream> using namespace std; int main() { int x;
Write a program that reads in 5 user numbers, and displays their inverse (1/x)
if the user enters a 0, print "Stop trying to break my program", and exits the loop
#include <iostream>
using namespace std;
int main() {
int x;
for (int count = 0; count < 5; count++) {
cout << "Please enter a number: ";
cin >> x;
cout << "The inverse of " << x << " is " << (1.0 / x) << endl; }
return 0;

131. #include <iostream> using namespace std; int main() { int x;
Write a program that reads in 5 user numbers, and displays their inverse (1/x)
if the user enters a 0, print "Stop trying to break my program", and exits the loop
#include <iostream>
using namespace std;
int main() {
int x;
for (int count = 0; count < 5; count++) {
cout << "Please enter a number: ";
cin >> x;
if (x == 0) {
cout << "Stop trying to break my program" << endl;
break; }
cout << "The inverse of " << x << " is " << (1.0 / x) << endl;
return 0;

133. Example: Write a program that reads in 5 user numbers, and displays their inverse (1/x)
if the user enters a 0, print "Stop trying to break my program", but continues the loop

134. #include <iostream> using namespace std; int main() { int x;
Write a program that reads in 5 user numbers, and displays their inverse (1/x)
if the user enters a 0, print "Stop trying to break my program", and continues the loop
#include <iostream>
using namespace std;
int main() {
int x;
for (int count = 0; count < 5; count++) {
cout << "Please enter a number: ";
cin >> x;
if (x == 0) {
cout << "Stop trying to break my program" << endl;
break; }
cout << "The inverse of " << x << " is " << (1.0 / x) << endl;
return 0;

135. #include <iostream> using namespace std; int main() { int x;
Write a program that reads in 5 user numbers, and displays their inverse (1/x)
if the user enters a 0, print "Stop trying to break my program", and continues the loop
#include <iostream>
using namespace std;
int main() {
int x;
for (int count = 0; count < 5; count++) {
cout << "Please enter a number: ";
cin >> x;
if (x == 0) {
cout << "Stop trying to break my program" << endl;
continue; }
cout << "The inverse of " << x << " is " << (1.0 / x) << endl;
return 0;

137. break and continue some consider both bad programming practice
break is somewhat common
continue is very uncommon
some consider both bad programming practice
difficult to follow code
can always be rewritten with conditional statements

138. #include <iostream> using namespace std; int main() { int x;
Write a program that reads in 5 user numbers, and displays their inverse (1/x)
if the user enters a 0, print "Stop trying to break my program", and exits the loop
#include <iostream>
using namespace std;
int main() {
int x;
for (int count = 0; count < 5; count++) {
cout << "Please enter a number: ";
cin >> x;
if (x == 0) {
cout << "Stop trying to break my program" << endl;
break; }
cout << "The inverse of " << x << " is " << (1.0 / x) << endl;
return 0;

139. #include <iostream> using namespace std; int main() {
Write a program that reads in 5 user numbers, and displays their inverse (1/x)
if the user enters a 0, print "Stop trying to break my program", and exits the loop
#include <iostream>
using namespace std;
int main() {
int x = 99;
for (int count = 0; (x != 0) && (count < 5); count++) {
cout << "Please enter a number: ";
cin >> x;
if (x == 0) {
cout << "Stop trying to break my program" << endl;
} else {
cout << "The inverse of " << x << " is " << (1.0 / x) << endl; }
return 0;

140. #include <iostream> using namespace std; int main() { int x;
Write a program that reads in 5 user numbers, and displays their inverse (1/x)
if the user enters a 0, print "Stop trying to break my program", and continues the loop
#include <iostream>
using namespace std;
int main() {
int x;
for (int count = 0; count < 5; count++) {
cout << "Please enter a number: ";
cin >> x;
if (x == 0) {
cout << "Stop trying to break my program" << endl;
continue; }
cout << "The inverse of " << x << " is " << (1.0 / x) << endl;
return 0;

141. #include <iostream> using namespace std; int main() { int x;
Write a program that reads in 5 user numbers, and displays their inverse (1/x)
if the user enters a 0, print "Stop trying to break my program", and continues the loop
#include <iostream>
using namespace std;
int main() {
int x;
for (int count = 0; count < 5; count++) {
cout << "Please enter a number: ";
cin >> x;
if (x == 0) {
cout << "Stop trying to break my program" << endl;
} else {
cout << "The inverse of " << x << " is " << (1.0 / x) << endl; }
return 0;

142. Loops – Summary three types of loops three styles of loop coding
while
for
do-while
three styles of loop coding
fixed count
sentinel-controlled
flag-controlled
loops can be nested
break and continue
artificial loop control
use with care