# C Program to Check whether a number is Prime Using Function

Problem: Write a C program to check whether given number is prime or not using function.

Solution: This C program accepts a number from user and passes it to a function named `isPrime()` which checks whether the input number is prime or not. Any natural number which is divisible by 1 and itself is known as prime number. So in `isPrime()` function we are using for loop to check if given number is divisible by any number between the range (1, number), if it divisible then it is not a prime number else it is a prime number.
```/* Aim: Write a function for the function prototype void isPrime(int n)*/

#include<stdio.h>
#include<stdlib.h>

void isPrime(int n); // isPrime Function Prototype

int main()
{
int n;

printf("\n Enter any number:- ");
scanf("%d",&n);

isPrime(n);

return 0;
}
// isPrime Function
void isPrime(int n)
{
int i,LED=0;

if(n<2)
printf("\n %d is not prime number \n \n",n);
exit(1);

for(i=2;i<=n/2;++i)
{
if(n%i==0)
LED=1;
break;
}

if(LED==0)
:printf("\n %d is prime number \n \n",n);
else
:printf("\n %d is not prime number \n \n",n);
}
```

### Output:

```[root@localhost ~]# gcc -o isPrime isPrime.c
[root@localhost ~]# ./isPrime

Enter any value:- 2

2 is prime number```