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  1. // Timothy Price CS1A Ch6 Challenge 21
  2. /*******************************************************************************
  3.  * Determine prime
  4.  *
  5.  * This program receives any number of integers and determines if they are
  6.  * prime numbers.
  7.  *
  8.  * Inputs:
  9.  * Integer or integers
  10.  *
  11.  * Outputs:
  12.  * Prime determination
  13. *******************************************************************************/
  14.  
  15. #include <iostream>
  16. #include <cmath>
  17.  
  18. using namespace std;
  19.  
  20. // Function prototype
  21. bool isPrime(int num);
  22.  
  23. int main() {
  24. int number;
  25.  
  26. cout << "-------- Prime Number Checker --------" << endl;
  27. cout << "Enter an integer (or enter 0 to exit): " << endl;
  28.  
  29. while (cin >> number && number != 0) {
  30. if (isPrime(number)) {
  31. cout << number << " is a prime number." << endl << endl;
  32. } else {
  33. cout << number << " is NOT a prime number." << endl << endl;
  34. }
  35. cout << "Enter another integer (or 0 to exit): " << endl;
  36. }
  37. cout << "Program ended." << endl;
  38. return 0;
  39. }
  40.  
  41. // Function to check if a number is prime
  42. bool isPrime(int num) {
  43. // Numbers less than or equal to 1 are not prime
  44. if (num <= 1) {
  45. return false;
  46. }
  47.  
  48. // Check for factors from 2 up to the square root of the number
  49. for (int i = 2; i <= sqrt(num); i++) {
  50. if (num % i == 0) {
  51. return false;
  52. }
  53. }
  54. // If number is prime, return true
  55. return true;
  56. }
Success #stdin #stdout 0s 5320KB
stdin
11
17
19
23
45
0
stdout
-------- Prime Number Checker --------
Enter an integer (or enter 0 to exit): 
11 is a prime number.

Enter another integer (or 0 to exit): 
17 is a prime number.

Enter another integer (or 0 to exit): 
19 is a prime number.

Enter another integer (or 0 to exit): 
23 is a prime number.

Enter another integer (or 0 to exit): 
45 is NOT a prime number.

Enter another integer (or 0 to exit): 
Program ended.