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# C Program to find whether a Number is Prime Or Composite using Recursion

• Prime Number: A number that is only divisible by 1 and itself.
• Composite Number: A number that is not a prime number.

Note: 1 is neither prime nor composite.

Below is a program to find whether the user input number is a prime number or a composite number using recursion.

``````#include<stdio.h>

// declaring the recursive function
int isPrime(int, int);

int main()
{
printf("\n\n\t\tStudytonight - Best place to learn\n\n\n");
int num, prime;
printf("Enter a positive number to check if Prime: ");
scanf("%d", &num);
prime = isPrime(num, num/2);
if(prime == 1)
{
printf("\n\n%d is a prime number\n\n", num);
}
else
{
printf("\n\n%d is a Composite number\n\n", num);
}
printf("\n\n\t\t\tCoding is Fun !\n\n\n");
return 0;
}

// function definition
int isPrime(int n, int i)
{
if(i == 1)
return 1;   // return statement terminates the recursive funtion
else
{
if(n%i == 0)
return 0;
else
isPrime(n, i-1);    // recursive call not using return statement
}
}``````