A prime number (or a prime) is a natural number greater than 1 that has no positive divisors other than 1 and itself.

For example,

5 is prime, as only 1 and 5 divide it.

Example Program (Method 1)

/* Example Program For Find Prime Number Using For Loop In C++
Pardeep Patel @ studywarehouse.com  */
#include<iostream>
#include<conio.h>
#include<math.h> // Math.h For sqrt function
using namespace std;

int main()
{

// Variable Declaration
int n;

// Get Input Value
cout<<"Enter the Number :";
cin>>n;

cout<<"List Of Prime Numbers Below "<<n<<endl;

//for Loop Block For Find Prime Number

for (int i=2; i<n; i++)
for (int j=2; j*j<=i; j++)
{
if (i % j == 0)
break;
else if (j+1 > sqrt(i)) {
cout << i << endl;
}
}

// Wait For Output Screen
getch();
return 0;
}

Sample Output:
Enter the Number: 50
List Of Prime Numbers Below 50
5
7
11
13
17
19
23
29
31
37
41
43
47

Example Program (Method 2)

/* Example Program For Find Prime Number Using For Loop In C++
Pardeep Patel @ studywarehouse.com  */

#include<iostream>
#include<conio.h>
#include<math.h> // Math.h For sqrt function

using namespace std;

int main()
{

// Variable Declaration
int n;

// Get Input Value
cout<<"Enter the Number :";
cin>>n;

cout<<"List Of Prime Numbers Below "<<n<<endl;

//for Loop Block For Find Prime Number
for (int i=2; i<n; i++)
{
bool prime=true;
for (int j=2; j*j<=i; j++)
{
if (i % j == 0)
{
prime=false;
break;
}
}
if(prime) cout << i << endl;
}

// Wait For Output Screen
getch();
return 0;
}

Sample Output:
Enter the Number :50
List Of Prime Numbers Below 50
5
7
11
13
17
19
23
29
31
37
41
43
47