title: @ in C header file
body: <p>Reading a header file, which implements the mapping of I/O devices for a microcontroller, I stumbled about the following code snippet: </p>
  
  <pre><code>typedef union{
      unsigned char Byte; 
      struct
      {
           unsigned char BIT0          :1;
           unsigned char BIT1          :1; 
           ...
           unsigned char BIT7          :1;
      }Bits; 
  }COP;
  
  extern volatile COP _COP @(0x0000 + 0x000000006FUL); 
  </code></pre>
  
  <p>I cannot make any sense of the last line since I do not know the @ Operator.</p>