# Prime Number program in C

Sure! Here’s an example of a program in C that checks whether a given number is prime or not:

```#include <stdio.h>

int isPrime(int num) {
if (num <= 1) {
return 0;  // not a prime number
}

for (int i = 2; i * i <= num; i++) {
if (num % i == 0) {
return 0;  // not a prime number
}
}

return 1;  // prime number
}

int main() {
int num;
printf("Enter a number: ");
scanf("%d", &num);

if (isPrime(num)) {
printf("%d is a prime number.\n", num);
} else {
printf("%d is not a prime number.\n", num);
}

return 0;
}
```

In this program, the `isPrime` function takes an integer as input and checks whether it is prime or not. It follows the basic primality test algorithm, where it iterates from 2 to the square root of the number and checks if any number divides the given number. If a divisor is found, the number is not prime.

In the `main` function, the user is prompted to enter a number, which is then passed to the `isPrime` function. Based on the return value, the program displays whether the number is prime or not.

Note: This program assumes that the input number is an integer greater than or equal to zero.

Categories C