C++ example to check whether a Number is Prime or Not

In this tutorial, we will discuss the concept of C++ example to check whether a Number is Prime or Not

In this post, we are going to learn how to check a number is prime or not using for, while and do-while loop in C++ programming language with Example program

Prime number

The number that can be divided by 1 and itself. it is called prime number

for Example 2,3,5,7,11,13…

C++ example to check whether a Number is Prime or Not — Check prime or not

C++ example to check a Number is Prime or Not

To understand this example programs, you should have previous knowledge of following C++ topics

For loop in C++ language

While loop in C++ language

Do while loop in C++ language

If statements in C++ language

Check the prime number using for loop

Program 1

#include <iostream>
#include <conio.h>
using namespace std;

int main()
{
    int num,i,count=0;

    cout<<"Enter the positive integer\n";
//Takes input from user
    cin>>num;
    for(i=2; i<=num/2; i++){

    //condition for non-prime
    if(num%i==0)
    {
        count=1;
        break;
    }
}

if(num==1){
        cout<<"you entered"<<num<<"\n";
    cout<<num<<" is neither a prime nor a composite number ";
}
else{
        if(count==0){
           cout<<"you entered" <<num<<"\n\n";
            cout<<num<<" is a prime number ";
        }
        else{
             cout<<"you entered: " <<num<<"\n\n";
            cout<<num<<" is not a prime number ";
        }
}
getch();
    return 0;
}

When the above code is executed, it produces the following results

Case 1

Enter the positive integer
45
you entered: 45
45 is not a prime number

Case 2

Enter the positive integer
43
you entered: 43
43 is a prime number

Case 3

Enter the positive integer
1
you entered 1
i is neither a prime nor a composite number

This program allows the user to enter a positive number and then it will check the given number is a prime number or not using for loop in C++ language

Check the prime number using while loop

Program 2

#include <iostream>
#include <conio.h>
using namespace std;

int main()
{
    int num,i,count=0;

    cout<<"Enter the positive integer\n";
//Takes input from user
    cin>>num;

    i=2;
    while(i<=num/2){

    //condition for non-prime
    if(num%i==0)
    {
        count=1;
        break;
    }
    i++;
}

if(num==1){
        cout<<"you entered "<<num<<"\n";
    cout<<num<<" is neither a prime nor a composite number ";
}
else{
        if(count==0){
           cout<<"you entered" <<num<<"\n\n";
            cout<<num<<" is a prime number ";
        }
        else{
             cout<<"you entered" <<num<<"\n\n";
            cout<<num<<" is not a prime number ";
        }
}
getch();
    return 0;
}

When the above code is executed, it produces the following results

Case 1

Enter the positive integer
99
you entered: 99
99 is not a prime number

Case 2

Enter the positive integer
97
you entered: 97
97 is a prime number

Case 3

Enter the positive integer
1
you entered 1
i is neither a prime nor a composite number

This program allows the user to enter a positive number and then it will check the given number is a prime number or not using while loop in C++ language

Check the prime number using the do-while loop

Program 3

#include <iostream>
#include <conio.h>
using namespace std;

int main()
{
    int num,i,count=0;

    cout<<"Enter the positive integer\n";
//Takes input from user
    cin>>num;

    i=2;
    do{

    //condition for non-prime
    if(num%i==0)
    {
        count=1;
        break;
    }
    i++;
}while(i<=num/2);

if(num==1){
        cout<<"you entered "<<num<<"\n";
    cout<<num<<" is neither a prime nor a composite number ";
}
else{
        if(count==0){
           cout<<"you entered" <<num<<"\n\n";
            cout<<num<<" is a prime number ";
        }
        else{
             cout<<"you entered" <<num<<"\n\n";
            cout<<num<<" is not a prime number ";
        }
}
getch();
    return 0;
}

When the above code is executed, it produces the following results

Case 1

Enter the positive integer
190
you entered: 190
190 is not a prime number

Case 2

Enter the positive integer
199
you entered: 199
199 is a prime number

Case 3

Enter the positive integer
1
you entered 1
i is neither a prime nor a composite number

This program allows the user to enter a positive number and then it will check the given number is a prime number or not using the do-while loop in C++ language

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