688: Highlights

• Header files should contain global variable declarations for every global variable that you expect to appear in more than one file.
• You can declare global variables as often as you like. You can define them only once.
• If you want to declare a global variable, then instantiate the following pattern:

  extern data type variable name; 
  

• If you want a global variable to be accessible from only those functions defined in the same file, then instantiate the following pattern:

  static data type variable name;