#command        Specify a user-defined command or translation directive
 #command...     continued
 #define         Define a manifest constant or pseudofunction
 #error          Generate a compiler error and display a message
 #ifdef          Compile a section of code if an identifier is defined
 #ifndef         Compile a section of code if an identifier is undefined
 #include        Include a file into the current source file
 #stdout         Send literal text to the standard output device             .
 #undef          Remove a #define macro definition
 #xcommand       Specify a user-defined command or translation directive