WRITE A PROGRAM NUMBER IS PRIME OR NOT

#include<stdio.h>
#include<conio.h>
// NO IS PRIME OR NOT
int Isprime(int no)
{
int i;
for(i=2;i<=no/2;i++)
{
if(no%i==0)
return 0;
}
return 1;
}
void main()
{ 
   int x;
   printf("%d",Isprime(18));
}