title: What is the '__IO' directive in GCC?
body: <p>I am working on an embedded device, and there is some code that was originally compiled using the IAR compiler.</p>
  
  <p>I am trying to recompile said code using the GCC compiler.</p>
  
  <p>There is a particular statement: <code>typedef __IO</code> , which simply doesn't get compiled ("Unrecognized symbol error"). </p>
  
  <p>Could anyone suggest how I could get this statement to compile properly?</p>