"Indefinite reference to`itoa' " message when trying to use itoia function

Question

I found on some websites people talked about using the itoa function to convert an integer number into a string containing the number in binary format.

Code example that should do this:

#include<stdio.h> 
#include<stdlib.h>

int main(){

 int i = 5; // Valor a ser convertido
 char c[33]; // Onde vou guardar o valor convertido (use o tamanho 33)

 itoa(i, c, 2);  // converter na base 2, acredito que converta até base 32

 printf("%s\n", c);

 getchar();
}

My intention is to make tests to see the results of the conversions before using in my program but when trying to copy I get the message :

Right away I thought that defines it with the Head file that contained the prototype of the function was missing, but according to the websites I consulted she is in stdlib. h.

I have tried to add some library, search error message among other things.

Like other examples like of that question also present a similar problem.

Can anyone explain to me why the problem occurs and how to solve ? Thanks in advance.