The Program in C that uses a function to determine whether a given positive integer is a prime number or not 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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