C++ Program to Print Prime Numbers

In this article, you will learn and get code to print prime numbers using a C++ program in the following ways:

Before creating these programs for the printing of prime numbers, let's first understand them.

What is a prime number?

If a number can't be divisible by any number except 1 and the number itself, then that number is called a prime number. For example, 2, 3, 5, 7, 13, 17, 19, etc.

Print prime numbers between 1 and 100

This program prints all prime numbers between 1 and 100 using the for loop. The question is, "Write a program in C++ to print prime numbers from 1 to 100." Here is its answer:

#include<iostream>
using namespace std;
int main()
{
    int i, chk=0, j;
    cout<<"Prime Numbers Between 1 to 100 are:\n";
    for(i=1; i<=100; i++)
    {
        for(j=2; j<i; j++)
        {
           if(i%j==0)
           {
               chk++;
               break;
           }
        }
        if(chk==0 && i!=1)
            cout<<i<<endl;
        chk = 0;
    }
    cout<<endl;
    return 0;
}

This program was built and runs under the Code::BlocksĀ IDE. Here is its sample output:

C++ program print prime numbers

The dry run of the above program goes like this:

C++ Print Prime Numbers in a Given Range

To print all prime numbers between a particular range (entered by the user) in C++ programming, do a divisibility test (as done in the previous program) using a for loop, from 2 to one less than that number (i.e., n-1). If the number is divided by any number from 2 to one less than that, then the number will not be prime. Otherwise, print it as a prime number, as shown here in the following program.

#include<iostream>
using namespace std;
int main()
{
    int st, en, i, j, chk=0;
    cout<<"Enter the Range\n";
    cout<<"Enter the Starting Number: ";
    cin>>st;
    cout<<"Enter the Ending Number: ";
    cin>>en;
    cout<<"\nPrime Numbers between "<<st<<" and "<<en<<" are:\n";
    for(i=st; i<=en; i++)
    {
        for(j=2; j<i; j++)
        {
           if(i%j==0)
           {
               chk++;
               break;
           }
        }
        if(chk==0 && i!=1)
            cout<<i<<endl;
        chk = 0;
    }
    cout<<endl;
    return 0;
}

Here is the initial output of this program's sample run:

print prime numbers in given range c++

Now enter the two numbers, say 10 and 50, as the starting and ending numbers to print all prime numbers between 10 and 50, as shown in the screenshot below:

c++ print prime numbers

The same program in different languages

C++ Quiz


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