1. Repetitive Structures
CSE1222: Lecture 7
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2. The Ohio State University
logExample.cpp
// example of log(k) for k = 1,2,..,8
. . .
int main() {
cout << "log(1) = " << log(1.0) << endl;
cout << "log(2) = " << log(2.0) << endl;
cout << "log(3) = " << log(3.0) << endl;
cout << "log(4) = " << log(4.0) << endl;
cout << "log(5) = " << log(5.0) << endl;
cout << "log(6) = " << log(6.0) << endl;
cout << "log(7) = " << log(7.0) << endl;
cout << "log(8) = " << log(8.0) << endl;
return 0; }
CSE1222: Lecture 7
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3. The Ohio State University
logExample.cpp
...
cout << "log(1) = " << log(1.0) << endl;
cout << "log(2) = " << log(2.0) << endl;
cout << "log(3) = " << log(3.0) << endl;
cout << "log(4) = " << log(4.0) << endl;
cout << "log(5) = " << log(5.0) << endl;
cout << "log(6) = " << log(6.0) << endl;
cout << "log(7) = " << log(7.0) << endl;
cout << "log(8) = " << log(8.0) << endl;
> logExample.exe
log(1) = 0
log(2) =
log(3) =
log(4) =
log(5) =
log(6) =
log(7) =
log(8) =
CSE1222: Lecture 7
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4. Repetition Structures (Loops)
Motivation:
Allow repetition of code (e.g., outputting from 1 to 1000 should not involve the programmer to write 1000 lines of cout statements!)
CSE1222: Lecture 7
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5. The Ohio State University
logWhile.cpp
// example of while loop for log(k) for k = 1,2,..,8
. . .
int main() {
int k(0);
k = 1;
while (k <= 8)
cout << "log(" << k << ") = "
<< log(double(k)) << endl;
k++; }
return 0;
CSE1222: Lecture 7
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6. The Ohio State University
logWhile.cpp
...
k = 1;
while (k <= 8) {
cout << "log(" << k << ") = "
<< log(double(k)) << endl;
k++; }
> logWhile.exe
log(1) = 0
log(2) =
log(3) =
log(4) =
log(5) =
log(6) =
log(7) =
log(8) =
CSE1222: Lecture 7
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7. The Ohio State University
while Loops
The while statement is of the form:
while (conditional expression) {
statement1;
statement2;
... }
CSE1222: Lecture 7
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8. The Ohio State University
How while Loops Work
First, the conditional expression is tested. If it is true, then the statement(s) within the loop structure is/are executed.
Once the end of those statements is reached, then the process is repeated.
If the expression ever evaluates to false, then the while statement is exited, and the program continues beyond the loop.
CSE1222: Lecture 7
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9. The Ohio State University
Types of Loops
Pretest Loops checks the looping condition first, then begins execution
while
for
Posttest Loops begins execution first, then checks looping condition
do-while
CSE1222: Lecture 7
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10. Control Flow of a while Loop
CSE1222: Lecture 7
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11. The Ohio State University
While Example
count = 1;
while (count <= 10) {
cout << count << “ “;
count++; //increment count! }
Output is “ ”
CSE1222: Lecture 7
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12. Control Flow of the Example Program
CSE1222: Lecture 7
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13. Repetition Structures 2
Motivation 2:
Allow repetition of code based on input (e.g., a program should be able to output n lines of cout statements where n is a user input.)
CSE1222: Lecture 7
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14. The Ohio State University
logWhile2.cpp
...
int main() {
int n(0), k(0);
cout << "Enter number of logarithms to compute: ";
cin >> n;
k = 1;
while (k <= n)
cout << "log(" << k << ") = "
<< log(double(k)) << endl;
k++; }
return 0;
Note: Header deleted in slide
CSE1222: Lecture 7
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15. The Ohio State University
logWhile2.cpp
...
cout << "Enter number of logarithms to compute: ";
cin >> n;
k = 1;
while (k <= n) {
cout << "log(" << k << ") = "
<< log(double(k)) << endl;
k++; }
> logWhile2.exe
Enter number of logarithms to compute: 5
log(1) = 0
log(2) =
log(3) =
log(4) =
log(5) =
CSE1222: Lecture 7
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16. The Ohio State University
logWhile2.cpp
...
cout << "Enter number of logarithms to compute: ";
cin >> n;
k = 1;
while (k <= n) {
cout << "log(" << k << ") = "
<< log(double(k)) << endl;
k++; }
What happens here?
> logWhile2.exe
Enter number of logarithms to compute: -3
???
CSE1222: Lecture 7
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17. Repetition Structures 3
If a program receives incorrect input, it can repeatedly prompt for the correct input.
CSE1222: Lecture 7
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18. The Ohio State University
logWhile3.cpp
// example of while loop to prompt for correct input
...
int main() {
double x(0.0);
cout << "Enter number: ";
cin >> x;
while (x <= 0)
cout << "Input must be positive." << endl; }
cout << "log(" << x << ") = “ << log(x) << endl;
return 0;
CSE1222: Lecture 7
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19. The Ohio State University
logWhile3.cpp
...
cout << "Enter number: ";
cin >> x;
while (x <= 0) {
cout << "Input must be positive." << endl; }
cout << "log(" << x << ") = " << log(x) << endl;
> logWhile3.exe
Enter number: -4.5
Input must be positive.
Enter number: 0
Enter number: 4.5
log(4.5) =
CSE1222: Lecture 7
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20. The Ohio State University
logWhileError.cpp
// example of a while loop with a logical error
. . .
int main() {
int k(0);
k = 1;
while (k <= 8)
cout << "log(" << k << ") = "
<< log(double(k)) endl; }
return 0;
Try running this program.
CSE1222: Lecture 7
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21. The Ohio State University
probability.cpp
...
int main() {
double p(0.0);
cout << "Enter probability player A wins 1 game: ";
cin >> p;
while (p < 0.0 || p > 1.0) {
cout << "Input must be in range [0:1]." << endl; }
cout << "Probability player A loses all 5 games = "
<< pow((1-p), 5.0) << endl;
return 0;
CSE1222: Lecture 7
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22. The Ohio State University
...
while (p < 0.0 || p > 1.0) {
cout << "Input must be in range [0:1]." << endl;
cout << "Enter probability player A wins 1 game: ";
cin >> p; }
> probability.exe
Enter probability player A wins: 2
Input must be in range [0:1].
Enter probability player A wins: -1
Enter probability player A wins: 0.2
Probability player A loses all 5 games =
>
CSE1222: Lecture 7
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23. The Ohio State University
temperature.cpp
// print a table converting fahrenheit to celsius
...
int fahrenheit(0), min_fahrenheit(0), max_fahrenheit(0);
int STEP_SIZE(10);
cout << "Enter min and max fahrenheit: ";
cin >> min_fahrenheit >> max_fahrenheit;
fahrenheit = min_fahrenheit;
// loop until fahrenheit is greater than max_fahrenheit
while (fahrenheit <= max_fahrenheit) {
// convert fahrenheit to celsius
float celsius = (fahrenheit ) * 5.0/9.0;
cout << "farenheit = " << fahrenheit
<< “ celsius = " << celsius << endl;
fahrenheit += STEP_SIZE; // increment by STEP_SIZE }
CSE1222: Lecture 7
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24. The Ohio State University
temperature.cpp
...
int STEP_SIZE(10);
fahrenheit = min_fahrenheit;
// loop until fahrenheit is greater than max_fahrenheit
while (fahrenheit <= max_fahrenheit) {
// convert fahrenheit to celsius
float celsius = (fahrenheit ) * 5.0/9.0;
cout << "farenheit = " << fahrenheit
<< “ celsius = " << celsius << endl;
fahrenheit += STEP_SIZE; // increment by STEP_SIZE }
> temperature.exe
Enter min and max fahrenheit:
farenheit = 20 celsius =
farenheit = 30 celsius =
farenheit = 40 celsius =
farenheit = 50 celsius = 10
farenheit = 60 celsius =
CSE1222: Lecture 7
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25. The Ohio State University
temperature.cpp
...
int STEP_SIZE(10);
fahrenheit = min_fahrenheit;
// loop until fahrenheit is greater than max_fahrenheit
while (fahrenheit <= max_fahrenheit) {
// convert fahrenheit to celsius
float celsius = (fahrenheit ) * 5.0/9.0;
cout << "farenheit = " << fahrenheit
<< “ celsius = " << celsius << endl;
fahrenheit += STEP_SIZE; // increment by STEP_SIZE }
> temperature.exe
Enter min and max fahrenheit:
farenheit = 25 celsius =
farenheit = 35 celsius =
farenheit = 45 celsius =
farenheit = 55 celsius =
CSE1222: Lecture 7
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26. The Ohio State University
temperature2.cpp
...
int STEP_SIZE(5);
fahrenheit = min_fahrenheit;
while (fahrenheit <= max_fahrenheit) {
float celsius = (fahrenheit ) * 5.0/9.0;
cout << "farenheit = " << fahrenheit
<< “ celsius = " << celsius << endl;
fahrenheit += STEP_SIZE; // increment by STEP_SIZE }
> temperature2.exe
Enter min and max fahrenheit:
farenheit = 25 celsius =
farenheit = 30 celsius =
farenheit = 35 celsius =
farenheit = 40 celsius =
farenheit = 45 celsius =
farenheit = 50 celsius = 10
farenheit = 55 celsius =
farenheit = 60 celsius =
CSE1222: Lecture 7
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27. The Ohio State University
temperatureError.cpp
// print a table converting fahrenheit to celsius
...
int fahrenheit(0), min_fahrenheit(0), max_fahrenheit(0);
int STEP_SIZE(10);
cout << "Enter min and max fahrenheit: ";
cin >> min_fahrenheit >> max_fahrenheit;
fahrenheit = min_fahrenheit;
// loop until fahrenheit does not equal max_fahrenheit
while (fahrenheit != max_fahrenheit) // Note != instead of <= {
// convert fahrenheit to celsius
float celsius = (fahrenheit ) * 5.0/9.0;
cout << "farenheit = " << fahrenheit
<< “ celsius = " << celsius << endl;
fahrenheit += STEP_SIZE; // increment by STEP_SIZE }
Try 20, 60. Try 0, Try 25, 75. Try 20, 75.
CSE1222: Lecture 7
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28. The Ohio State University
sinWhile.cpp (Error) …
int main() {
double x(0.0);
double increment(0.1);
cout.setf(ios::fixed);
while (x != 1.0)
cout << x << ": " << sin(x) << " " << cos(x) << endl;
x += increment; }
return 0;
CSE1222: Lecture 7
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29. The Ohio State University
for Loops
CSE1222: Lecture 7
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30. The Ohio State University
logFor.cpp
// example of for loop for log(k) for k = 1,2,..,8
#include <iostream>
#include <cmath>
using namespace std;
int main() {
for (int k = 1; k <= 8; k++)
cout << "log(" << k << ") = "
<< log(double(k)) << endl; }
return 0;
CSE1222: Lecture 7
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31. The Ohio State University
logFor.cpp
...
for (int k = 1; k <= 8; k++) {
cout << "log(" << k << ") = "
<< log(double(k)) << endl; }
> logFor.exe
log(1) = 0
log(2) =
log(3) =
log(4) =
log(5) =
log(6) =
log(7) =
log(8) =
CSE1222: Lecture 7
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32. The Ohio State University
for Loop Syntax
for (initialize; condition; alter) {
statement1;
statement2;
statement3;
statement4;
... }
CSE1222: Lecture 7
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33. The Ohio State University
for Loop Syntax (2)
Initializing list
A statement to set the starting value(s) of variables (normally a loop counter)
Expression
The looping condition
Altering list
Statement that is executed at the end of every loop traversal
Normally determines how the counter is manipulated after each pass through the loop
Important note: At the end of a pass through the loop, the statements in the altering list is executed BEFORE the loop expression is evaluated.
CSE1222: Lecture 7
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34. The Ohio State University
How for Loops Work
First, the initialization statements are executed.
Then the conditional expression is tested. If it is true, then the statement(s) within the loop structure is/are executed.
Once the end of those statements is reached, then altering statements are executed, and the process is repeated.
If the expression ever evaluates to false, then the loop statement is exited, and the program continues beyond the loop.
CSE1222: Lecture 7
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35. Control Flow of a for Loop
CSE1222: Lecture 7
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36. The Ohio State University
for Loop Example
for (int k = 1; k <= 8; k++) {
cout << "log(" << k << ") = "
<< log(double(k)) << endl; }
// the while-loop equivalent:
int k(0);
. . .
k = 1;
while (k <= 8)
k++;
CSE1222: Lecture 7
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37. The Ohio State University
for Loop Example2
// Compute n logarithms:
for (int k = 1; k <= n; k++) {
cout << "log(" << k << ") = "
<< log(double(k)) << endl; }
// the while-loop equivalent:
int k(0);
. . .
k = 1;
while (k <= n)
k++;
CSE1222: Lecture 7
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38. (Too) Clever for Loop Example
double x(0.0);
cout << “Enter Number: “;
for (cin >> x; x <= 0; cin >> x) // a while loop is better {
cout << "Input must be positive." << endl;
cout << "Enter number: "; }
// the while-loop equivalent:
cout << “Enter number: “;
cin >> x;
while (x <= 0)
cout << "log(" << x << ") = " << log(x) << endl;
CSE1222: Lecture 7
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39. The Ohio State University
for Loops
for loops and while loops are interchangeable.
A for loop is a pre-test loop
Whether to use a while or a for loop is a question of style and readability.
Use for loops to count from a to b;
Use while loops to iterate until some condition is satisfied.
CSE1222: Lecture 7
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40. The Ohio State University
for Loop Example4
for (int k = 1; k <= 8; k++) {
cout << "log(" << k << ") = "
<< log(double(k)) << endl; }
cout << k << endl; // SYNTAX ERROR
// Variable k can be declared before the for-loop
int k(0);
for (k = 1; k <= 8; k++)
cout << k << endl; // What is the value of k?
CSE1222: Lecture 7
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41. The Ohio State University
Using Nested Loops
A loop inside of another loop
Extremely useful and very common
for (int i = 1; i <= 5; i++) {
cout << “i is now “ << i << endl;
//inner (nested) loop
for (int j = 1; j <= 4; j++)
cout << “j is now “ << j << endl; }
} //What is the output?
CSE1222: Lecture 7
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42. The Ohio State University
CSE1222: Lecture 7
The Ohio State University

43. Nested for loops: square.cpp
// print a square of x's
...
int length(0);
cout << "Enter square edge length: ";
cin >> length;
for (int row = 1; row <= length; row++) {
// print length x's
for (int col = 1; col <= length; col++)
cout << "x"; }
cout << endl; // print newline to finish row
CSE1222: Lecture 7
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44. Nested for loops: square.cpp
...
for (int row = 1; row <= length; row++) {
// print length x's
for (int col = 1; col <= length; col++)
cout << "x"; }
cout << endl; // print newline to finish row
> square.exe
Enter square edge length: 6
xxxxxx
CSE1222: Lecture 7
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45. Nested for loops: diagonal.cpp
// print a diagonal of x's
...
int length(0);
cout << "Enter diagonal length: ";
cin >> length;
for (int row = 1; row <= length; row++) {
// print (row-1) spaces
for (int col = 1; col <= row-1; col++)
cout << " "; }
cout << "x" << endl; // print x on diagonal
CSE1222: Lecture 7
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46. Nested for loops: diagonal.cpp
...
for (int row = 1; row <= length; row++) {
// print (row-1) spaces
for (int col = 1; col <= row-1; col++)
cout << " "; }
cout << "x" << endl; // print x on diagonal
> diagonal.exe
Enter diagonal length: 6 x
CSE1222: Lecture 7
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47. The Ohio State University
squareError.cpp
// version of square.cpp with errors
...
int length(0);
cout << "Enter square edge length: ";
cin >> length;
for (int row = 1; row <= length; row++); {
// print length x's
for (int col = 1; col <= length; col++);
cout << "x"; }
cout << endl; // print newline to finish row
Will this program compile?
What will it output when it runs?
CSE1222: Lecture 7
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48. The Ohio State University
do-while loops
A do-while loop checks the condition at the end of the loop;
Example:
char c(‘n’); do {
... //rest of the program
cout << “Do you wish to continue: “;
cin >> c; }
while (c == ‘y’ || c == ‘Y’);
See text for more details.
CSE1222: Lecture 7
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49. The Ohio State University
Conclusion on Loops
Loops are generally used for repetition of a section of code.
There are three basic types:
while, for, and do-while
while and for are pretest (entrance controlled)
do-while is posttest (exit controlled)
CSE1222: Lecture 7
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50. Common Programming Errors (1)
Use == when comparing for equivalence in while, for, and do-while statements! (Same as using == in if-statements.)
Precision problem:
double x, y;
. . .
“while (x != y)” may always be true even though mathematically x should equal y.
CSE1222: Lecture 7
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51. Common Programming Errors (1)
For each statement, what is the output?
for (int i = 1; i < 7; i++)
{ cout << i << endl; }
for (int i = 1; i <= 7; i++)
for (int i = 0; i <= 7; i++)
for (int i = 0; i < 7; i++)
CSE1222: Lecture 7
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52. Common Programming Errors (1)
For each statement, what is the output?
for (int i = 1; i < 7; i++)
{ cout << i; } {
cout << “Row “ << i;
for (int j = 1; j < 4; j++)
{ cout << “ Col “ << j << endl; } }
CSE1222: Lecture 7
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53. Common Programming Errors (2)
Do not place a semicolon at the end of a for statement:
int i;
for (i = 1; i <= 10; i++);
{ cout << “i = “ << i << endl; }
What does this output?
Outputs: i = 11
CSE1222: Lecture 7
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54. Common Programming Errors (3)
Use semicolons, not commas, to separate items in a for statement:
for (i=0, i<10, i++) //invalid
for (i=0; i<10; i++) //valid
Do not forget the semicolon at the end of the while statement in a do-while loop
do {
...
} while(x > 0);
CSE1222: Lecture 7
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55. Loop Programming Techniques
CSE1222: Lecture 7
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56. Interactive Input with a loop
int main() {
double x(0.0), total(0.0), average(0.0);
const int NUM_INPUTS(4);
total = 0.0;
for (int i = 0; i < NUM_INPUTS; i++)
// ask user for a number
cout << "Enter a number: ";
cin >> x;
total = total + x; }
average = total / NUM_INPUTS;
cout << "The average of the entered values is: "
<< average << endl;
CSE1222: Lecture 7
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57. Selection within a Loop
int main() {
double x(0.0), postot(0.0), negtot(0.0);
const int NUM_INPUTS(5);
// NOTE: postot and negtot initialized to 0.
for (int i = 1; i <= NUM_INPUTS; i++)
cout << "Enter a number: ";
cin >> x;
// Selection: Separate positive from negative inputs.
if (x > 0)
{ postot = postot + x; }
else
{ negtot = negtot + x; } }
cout << "The positive total is " << postot << endl;
cout << "The negative total is " << negtot << endl;
return(0);
CSE1222: Lecture 7
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58. Selection within a Loop (2)
int main() {
double x(0.0), postot(0.0), negtot(0.0);
cout << "Enter a number: ";
cin >> x;
// NOTE: postot and negtot initialized to 0.
while (x != 0.0)
// Selection: Separate positive from negative inputs.
if (x > 0)
{ postot = postot + x; }
else
{ negtot = negtot + x; } }
cout << "The positive total is " << postot << endl;
cout << "The negative total is " << negtot << endl;
. . .
CSE1222: Lecture 7
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59. Evaluating Functions of One Variable
// Calculates several values for y = 10x² + 3x - 2
int main() {
int x(0), y(0), xmin(0), xmax(0);
cout << "Minimum and maximum x values: ";
cin >> xmin >> xmax;
for (x = xmin; x <= xmax; x++)
y = 10 * pow(x, 2) + 3 * x – 2;
cout << "x = " << x
<< " f(x) = " << y << endl; }
CSE1222: Lecture 7
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60. Prompting for Correct Input
int main() {
const int MAX_AGE(125);
int age(0);
cout << “Enter your age (1-“ << MAX_AGE << “):”;
cin >> age;
while (age <= 0 || age > MAX_AGE)
cout << “Invalid input. Try again.” << endl; }
CSE1222: Lecture 7
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61. Summation: Sum of Cubes
...
int main() {
long sum(0);
int n(0);
cout << “Enter number of terms in the summation: “;
cin >> n;
for (int i = 1; i <= n; i++)
sum += i*i*i; }
cout << “1^3 + 2^3 + 3^ “
<< n << “^3 = “ << sum << endl;
return 0;
CSE1222: Lecture 7
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62. Summation Over Two Variables
Input: n
Compute 𝑖=0 𝑛 𝑗=0 𝑖 𝑖−𝑗 .
Outputs: i = 11
CSE1222: Lecture 7
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63. Summation Over Two Variables
Compute 𝑖=0 𝑛 𝑗=0 𝑖 𝑖−𝑗 .
Table of (i-j) (where j ≤ i):
(i-j)
j=0
j=1
j=2
j=3
...
i=0
i=1 1
i=2 2
i=3 3
Outputs: i = 11
CSE1222: Lecture 7
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64. Summation Over Two Variables
Input: n
Compute 𝑖=0 𝑛 𝑗=0 𝑖 𝑖−𝑗 .
Algorithm:
sum ← 0;
for i ← 0 to n do
for j ← 0 to i do
sum ← sum + (i-j);
Outputs: i = 11
CSE1222: Lecture 7
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65. The Ohio State University
Algorithm
From “Programming and Problem Solving with C++” By Nell Dale:
An algorithm is “a step-by-step procedure for solving a problem”.
CSE1222: Lecture 7
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66. Summation Over Two Variables
Input: n
Compute 𝑖=0 𝑛 𝑗=0 𝑖 𝑖−𝑗 .
Algorithm:
sum ← 0;
for i ← 0 to n do
for j ← 0 to i do
sum ← sum + (i-j);
Outputs: i = 11
CSE1222: Lecture 7
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67. Summation over two variables
...
int main() {
long sum(0); // Initialize sum to zero
int n(0);
cout << "Enter max value of i: ";
cin >> n;
for (int i = 0; i <= n; i++)
for (int j = 0; j <= i; j++)
sum = sum + (i-j); }
cout << "sum_{i=0}^n sum_{j=0}^i (i-j) = " << sum << endl;
return 0;
CSE1222: Lecture 7
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68. Printing a table using nested loops
Input: n
Output: Table of 1/(i-j)2 for i = 1,...,n and j = 1,...,n.
Don’t print anything when i = j. Why?
CSE1222: Lecture 7
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69. Printing a table using nested loops
Input: n
Output: Table of 1/(i-j)2 for i = 1,...,n and j = 1,...,n.
Algorithm:
for i ← 1 to n do
for j ← 1 to n do
if (i ≠ j) print 1/(i-j)2
else print "******"
print newline; (Why?)
CSE1222: Lecture 7
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70. Printing a table using nested loops
...
int main() {
int numRows(0);
int diff(0);
cout << "Enter number of table rows: ";
cin >> numRows;
cout.setf(ios::fixed); // fixed precision output
CSE1222: Lecture 7
The Ohio State University

71. Printing a table using nested loops
...
for (int i = 1; i <= numRows; i++) {
for (int j = 1; j <= numRows; j++)
if (i != j)
diff = i-j;
cout << " " << 1.0/(diff*diff); }
else
cout << " ****** ";
cout << endl; // end row
CSE1222: Lecture 7
The Ohio State University

72. The Ohio State University
for (int i = 1; i <= numRows; i++){
for (int j = 1; j <= numRows; j++) {
if (i != j) {
diff = i-j;
cout << " " << 1.0/(diff*diff); }
else
{ cout << " ****** "; }
cout << endl; // end row
> printTable.exe
Enter number of table rows: 6
******
******
******
******
******
******
>
CSE1222: Lecture 7
The Ohio State University

73. The Ohio State University
Problem: Print primes
Print prime numbers between 2 and n.
CSE1222: Lecture 7
The Ohio State University

74. The Ohio State University
Print prime numbers
Input: n
Output: Prime numbers between 2 and n.
Algorithm:
for k ← 2 to n do
flag_composite ← false;
for j ← 2 to k-1 do
if (k mod j = 0) then
flag_composite ← true;
if (flag_composite = false) print k.
CSE1222: Lecture 7
The Ohio State University

75. The Ohio State University
prime.cpp
...
int main() {
int n(0);
bool flag_composite(false);
cout << "Enter n: ";
cin >> n;
CSE1222: Lecture 7
The Ohio State University

76. The Ohio State University
prime.cpp
...
cout << "Prime numbers:" << endl;
for (int k = 2; k <= n; k++) {
flag_composite = false;
for (int j = 2; j < k; j++)
if (k%j == 0) // if (k mod j == 0)
flag_composite = true; }
if (!flag_composite)
cout << k << endl; // k is prime
CSE1222: Lecture 7
The Ohio State University

77. The Ohio State University
for (int k = 2; k <= n; k++) {
flag_composite = false;
for (int j = 2; j < k; j++) {
if (k%j == 0) // if (k mod j == 0)
{ flag_composite = true; } }
if (!flag_composite)
{ cout << k << endl; } // k is prime
> prime.exe
Enter n: 20 2 3 5 7 11 13 17 19
CSE1222: Lecture 7
The Ohio State University

78. The Ohio State University
Summary
while loops:
Repeat until some condition is fulfilled;
Pretest loop.
for loops:
Used for counting;
3 parts: for (initialize; condition; alter){...}
do-while loops:
Example: “Do you wish to continue?”
Posttest loop.
CSE1222: Lecture 7
The Ohio State University