**The Program in C that uses a function to determine whether a given positive integer is a prime number or no**t **is given below**:

```
#include <stdio.h>
int is_prime(int num) {
if (num <= 1) {
return 0;
}
for (int i = 2; i < num; i++) {
if (num % i == 0) {
return 0;
}
}
return 1;
}
int main() {
int num;
printf("Enter a positive integer: ");
scanf("%d", &num);
if (is_prime(num)) {
printf("%d is a prime number.\n", num);
} else {
printf("%d is not a prime number.\n", num);
}
return 0;
}
```

## Output:

Enter a positive integer: 6

6 is not a prime number.

## Pro-Tips**💡**

In this program, `is_prime`

is the function that determines whether a given positive integer is a prime number or not.

The function takes one parameter: the positive integer to check. The function first checks if the number is less or equal to 1, and if it is, it returns 0 (not prime).

Then it uses a for loop to iterate through the integers from 2 to `num-1`

and check if `num`

is divisible by any of them using the modulus operator `%`

.

If it is divisible by any of them, then it is not prime so it will return 0. If it is not divisible by any of them, then it is a prime number, so it will return 1.

The main function prompts the user for a positive integer, then calls the `is_prime`

function to check if it is a prime number and print the result

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