647: Highlights

• If you want to have two or more versions of a file, then you can arrange for conditional compilation.
• If you want to have certain lines of code compiled conditionally, then define a control symbol by instantiating the following pattern:

  #define control symbol 
  

  and then surround the lines of code as follows:

  #ifdef control symbol 
  lines to be compiled if control symbol is defined 
  #else 
  lines to be compiled if control symbol is not defined 
  #endif