The .cstack file format is a property list that has the following keys and values.  The comments denote how the file is stored internally.

{
  // The values in the Languages dictionary is stored in two NSString instance 
  // variables in the StackModel class.

  Languages = 
    {
	FirstValue = NSString;				
	SecondValue = NSString;
    };

  // The Notes string is stored in an NSString instance variable in the
  // StackModel class.

  Notes = NSString;

  // The Schedule array is stored in an NSArray instance variable in the    
  // Scheduler class. The Time is stored as an NSDate, and the Title is 
  // stored as an NSString.
 
  Schedule = (
    {
    Time = NSString;
    Title = NSString;
    }
  );

  // The State array is stored in an NSArray instance variable in the
  // Scheduler class. Slot and Cards values are stored as NSNumbers. The
  // The Title is stored as an NSString. Time values are stored as NSDates.

  State = (
    {
    Slot = NSString;
    Title = NSString;
    Cards = NSString;
    Time = NSString;
    Times = (
      {
      Time = NSString;
      Slot = NSString;
      Cards = NSString;
      }
    );
    }
  );

  // The Words array is stored in an NSArray instance variable in the
  // StackModel class. The NSArray is an array of CardModel objects.
  // the CardModel class stores FirstValue and SecondValue as NSStrings,
  // Slot as an NSnumber, and Time as an NSDate. The History array is 
  // stored as an NSarray in the CardModel Class. Time is stored as an
  // NSDate, and Result is strored as an NSString. (Pass or Fail)

  Words = (
	{
	FirstValue = NSString;
	SecondValue = NSString;
	Slot = NSString;
	Time = NSString;
	History = (
	  {
	  Time = NSString;
	  Result = NSString;
	  }
    );
  );
}