A Program to Check a Prime Number
In this example, we are giving a program to check whether a number is prime or not. A number can be said prime if the number is divisible only by 1 and itself. For example: 2, 3, 5, 7, 11, 13, 17, 19 etc.
Program to check prime:
#include <stdio.h>
int main() {
int n, i, flag = 0;
printf("Enter a positive integer: ");
scanf("%d", &n);
for (i = 2; i < n / 2; ++i) {
// condition for non prime number
if (n % i == 0) {
flag = 1;
break;
}
}
if (n == 1) {
printf("1 is neither prime nor composite.");
}
else {
if (flag == 0)
printf("%d is a prime number.", n);
else
printf("%d is not a prime number.", n);
}
return 0;
}
Output:
Enter a positive integer: 7 7 is a prime number.