C Program to Check a number whether it is prime or not Using for loop

1. 
   
3. //C Program to Check a number whether it is prime or not using for loop
4. 
   
5. #include <stdio.h>
6. int main() {
7.     int number, i, a = 0;
8.     printf("Enter a positive Number To Check whether it is prime or not:- ");
9.     scanf("%d", &number);
10. 
    
12.  if(number<0)
13.     {
14.         printf("You Entered Negative Number , Please Enter Positive Number.");
15.         exit(0);
16.      }
17. 
    
18.     for (i = 2; i <= number / 2; ++i) {
19. 
    
20.         if (number % i == 0) {
21.             a = 1;
22.             break;
23.         }
24.     }
25. 
    
26.     if (number == 1) {
27.         printf("1 is neither prime number nor composite number.");
28.     }
29.     else {
30.         if (a == 0)
31.             printf("%d is a prime number.", number);
32.         else
33.             printf("%d is not a prime number.", number);
34.     }
35. 
    
36.     return 0;
37. }

Output