c - Floating Point Exception from my for loop that is not initialized correctly -

i keep getting floating point expection on program trying determine if number prime or not in c. used loop:

for(i=1:i<num/2:i++)    (if num%i==0)  

then prime. please help!

stopping @ square root of num variable sufficient , here's sample code doing job you're asking in correct form :

#include <stdio.h> #include <math.h> void main() {  int i,num;  printf("enter number check if prime or not : ");  scanf("%d",&num);   for(i=2 ; <= (int)sqrt(num) ; i++)   if(num%i==0)    {     printf("%d not prime ",num);     break;   }  if(i > (int)sqrt(num))    printf("%d prime"); }