18.20. Write a function that gets any positive integer and determine prime or not prime.

#include<stdio.h>
#include<conio.h>
#include<math.h>
int is prime (long n)
{
int i, t;
if (n<2)
return 0;
t=sqrt (n);
for (i=2; i<=t; i++)
if (n%i==0)
return 0;
return 1;
}
void main ()
{
long n;
clrscr();
printf("Enter any positive integer”);
scanf ("%ld", &n);
if (isprime (n)==1)
printf ("Prime");
else
printf("Not prime");
getch();
}