# C++ Exercises: List non-prime numbers from 1 to an upperbound

## C++ For Loop: Exercise-16 with Solution

Write a C++ program to list non-prime numbers from 1 to an upperbound.

**Pictorial Presentation:**

**Sample Solution** :-

**C++ Code :**

```
#include <iostream>
#include <cmath>
using namespace std;
int main()
{
int ult;
cout << "\n\n List non-prime numbers from 1 to an upperbound:\n";
cout << "----------------------------------------------------\n";
cout << " Input the upperlimit: ";
cin >> ult;
cout << " The non-prime numbers are: " << endl;
for (int num = 2; num <= ult; ++num)
{
int mfactor = (int)sqrt(num);
for (int fact = 2; fact <= mfactor; ++fact)
{
if (num % fact == 0)
{
cout << num << " ";
break;
}
}
}
cout << endl;
return 0;
}
```

Sample Output:

List non-prime numbers from 1 to an upperbound: ---------------------------------------------------- Input the upperlimit: 25 The non-prime numbers are: 4 6 8 9 10 12 14 15 16 18 20 21 22 24 25

**Flowchart: **

**C++ Code Editor:**

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**Previous:** Write a program in C++ to asked user to input positive integers to process count, maximum, minimum,
and average or terminate the process with -1.

**Next:** Write a program in C++ to print a square pattern with # character.

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