Introduction

Control Statement

- Program to the sum of natural numbers
- Program to check leap year
- Program to find factorial of the number
- Program to find reverse of the number
- Program to Check Armstrong Number
- Program to find the sum of Natural Numbers using Recursion
- Calculator Program
- Program to identify day of week
- Program to print Fibonacci series

Function

- Program to convert Binary to Octal Number
- Program to convert Octal to Binary Number
- Program to find reverse of the sentence using Recursion
- Program to Shutdown and restart Computer
- Program to find the area of triangle
- Program to find LCM
- Program to check prime number using Functions
- Program to convert Binary to Decimal Number
- Program to convert Decimal to Binary Number

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OOPS

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# Program to check whether the number is prime or not

In this article, We will check whether number is prime is not.

Prime Numbers are those numbers which is divisible by 1 and itself. Eg: 2,3,5,7,11 etc.

We will check the prime number by simply dividing all the number below that number. Suppose, If we have to check the 5 then we will divide 5 by 2,3 and 4. If the anyone gives remainder 0 then that is not a prime.

Let’s look and example to make clear concepts

```
#include<iostream>
using namespace std;
int main()
{
int num, i, flag = 0;
cout << "Enter a Number: ";
cin >> num;
for( i = 2; i < num; i++)
{
if( num % i == 0)
{
flag = 1;
break;
}
}
if( flag == 0 )
cout << "\nIt is a Prime Number" << endl;
else
cout << "\nIt is not a Prime Number" << endl;
return 0;
}
```

The output of above program is

```
Enter a number : 5
It is a Prime Number
Enter a number : 6
It is not a Prime Number
```

Let’s understand how program working:

**Step 1:**First we will initialize variables num, i and flag = 1**Step 2:**We will read the number**Step 3:**We will loop from 2 to that number. If any number gives remainder while dividing then we will set flag = 1**Step 4:**After loop end, We will change whether flag value is o or 1. If flag value has initial value then number is prime else number is not prime.

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