title: Where / How is null defined?
body: <p>Null is not declared?</p>
  
  <p>My code:</p>
  
  <pre><code>// Include necessary libraries
  #include &lt;cstdlib&gt; // Exits
  #include &lt;iostream&gt; // I/O
  #include &lt;cstring&gt; // String functions
  using namespace std;
  
  int main(int argc, char *argv[])
  {
      //Declare local Constants and Variables
      const char SOKINP[19] = "23456789TtJjQqKkAa"; // Valid Input Characters
      char acCards [5]; // Array to hold up to five cards (user input)
      bool bErr;        // Loop on Error (Calculated)
      int  i,           // Loop variable (Calculated)
      iNbrCrd,          // Number of Cards 2-5 (user input)
      iNAces,           // Number of Aces (Calculated)
      iTS;              // Total Score (Calculated)
  
      ...
  
      for (i=0;i&lt;iNbrCrd;i++){
         do {
             cout &lt;&lt; "Enter Card #" &lt;&lt; i &lt;&lt; " (2-9,t,j,q,k or a)  &gt;";
             cin  &gt;&gt; acCards[i];
             cout &lt;&lt; endl;
             bErr = (strchr(SOKINP, acCards[i]) == null) ? true : false; // *ERROR*
         } while (bErr);
      }
      return EXIT_SUCCESS;
  }
  </code></pre>
  
  <p>[Error] 'null' was not declared in this scope</p>
  
  <p>How do I declare 'null'?  I tried including several other libraries.
  I'm using Dev C++ v5.4.2</p>
  
  <p>Thanks, ~d</p>