Why my while loop in OCaml doesn't work as expected?

Question

I am trying to translate this C code to OCaml code, which should check if the input int is prime number or not. My C code works, but my ocaml code doesn't even run.

void is_prime(int pri){
    int a=2;
    int b=poww(a,2);
    while(b<=pri){
       int resu=pri%a;
       if(resu==0) {
            printf("False");
            return 0;
       }
       a++;
       b=poww(a,2);
    }
    printf("True");
}

And this is my OCaml code:

let is_prime n = 
  let a= ref 2 in
  let b= ref (pow !a 2) in 
  let c= ref true in
  while !b<n do
    let resu= (n mod !a) in
    if resu=0 then c:=false;
    a:=!a+1;
    b:=(pow !a 2);
  done in
  if c=false then false
  else true
;;

What I want is an OCaml code takes an int as input and output a boolean. pow in my OCaml code is an existing function pow ab (where a and b are int and output a^b). For some reason, the code doesn't work...

Update: problem solved New Ocaml code that works:

let is_prime n = 
  if n>1 then
    let a= ref 2 in
    let b= ref (pow !a 2) in 
    let c= ref true in

    while !b<n do
    (*ignore (Printf.printf "abc");*)
      let resu= (n mod !a) in
      if resu=0 then c:=false;
      a:=!a+1;
      b:=(pow !a 2);
    done;
    if !c then true
    else false
  else raise Domain
;;

Answer 1

One possibility: your C code has while (b <= pri) . Your OCaml code has while !b < n . The meanings of <= in C and < in OCaml are different.