How to Write C++ Program to Find Prime Number

How to Find Prime Number in C++

Welcome to Virtual Study Solutions C++ Tutorial. Today we will discuss and learn how to Find Prime Number in C++ Programming.

Topics we will cover in this tutorial will be as follows:

1. What is a Prime Number
2. C++ Program to Find Prime Number
3. Prime Number C++ Program Logic
4. Example Code to Find Prime Number

 C++ Program to Find Prime Number

What is a PRIME NUMBER

Prime Number is a Natural number which is greater than 1 and it has only two divisor 1 and itself is Called Prime number ".

Lets take a Example:

2, 3, 5, 7 is prime Number, because it has only two divisors 1 and itself.

Also Read: How to write C++ program to find Fibonacci Series

C++ Program To Find Prime Number

#include<iostream.h>

#include<conio.h>

void main()

{

//clrscr();

int number,count=0;

cout<<"ENTER NUMBER TO CHECK IT IS PRIME OR NOT ";

cin>>number;

for(int a=1;a<=number;a++)

{

if(number%a==0)

{

count++;

}

}

if(count==2)

{

cout<<" PRIME NUMBER \n";

}

else

{

cout<<" NOT A PRIME NUMBER \n";

}

//getch();

}

Prime Number C++ Program Logic

To Understand the C++ Program logic to find Prime number first of all Recall PRIME NUMBER definition which is " a number which divides by 1 and itself ".

So we in our program we will make a condition like that in which user will enter a number and our program will check it by dividing it from 1 up to itself.

To check that how much times it has divided to numbers from 1 to itself we take a variable and increment it each times when a number is divided.

Also Read: How to write C++ Program to find factorial of Number

As You may already Know in C++ Programming we take a FOR LOOP which will start from 1 up to number that has entered to check whether it is PRIME NUMBER or not with in FOR LOOP we will set an IF condition and place counter (count++) variable in its body so whenever a number from 1 to number which has entered to check divides than IF condition becomes true and counter variable will be incremented.

When FOR LOOP is completed we check from IF condition that:

• if counter variables value is equal to 2 than number is PRIME 
• else NUMBER IS NOT PRIME.

Because if number divided two times by 1 and itself counter variable will incremented two times if more than two times counter variable will have value greater than 2. 

Also Read: What is Recursive function in c++ with Examples

Example Code to Find Prime Number

Here is the Example Code of C++ Program to Find Prime Number Screenshot:

Example Code to Find Prime Number in C++ 

Code output to Find Prime Number

Here is the Sample Output of Example program to find Prime Number:

Sample Output of Example program to find Prime Number

We Recommended You to change the logic of above Program For fast learning and do experiments with codes.