// constructors and destructor:

   stackClass();  // default constructor
   // copy constructor and destructor are
   // supplied by the compiler

// stack operations:
   bool StackIsEmpty() const;
   // Determines whether a stack is empty.
   // Precondition: None.
   // Postcondition: Returns true if the stack is empty;
   // otherwise returns false.

   void Push(stackItemType NewItem, bool& Success);
   // Adds an item to the top of a stack.
   // Precondition: NewItem is the item to be added.
   // Postcondition: If insertion was successful, NewItem
   // is on the top of the stack and Success is true;
   // otherwise Success is false.

   void Pop(bool& Success);
   // Removes the top of a stack.
   // Precondition: None.
   // Postcondition: If the stack was not empty, the item
   // that was added most recently is removed and Success
   // is true. However, if the stack was empty, deletion is
   // impossible and Success is false.

   void Pop(stackItemType& StackTop, bool& Success);
   // Retrieves and removes the top of a stack.
   // Precondition: None.
   // Postcondition: If the stack was not empty, StackTop
   // contains the item that was added most recently, the
   // item is removed, and Success is true. However, if the
   // stack was empty, deletion is impossible, StackTop is
   // unchanged, and Success is false.

   void GetStackTop(stackItemType& StackTop,
                    bool& Success) const;
   // Retrieves the top of a stack.
   // Precondition: None.
   // Postcondition: If the stack was not empty, StackTop
   // contains the item that was added most recently and
   // Success is true. However, if the stack was empty, the
   // operation fails, StackTop is unchanged, and Success
   // is false. The stack is unchanged.

   stackItemType Items[MAX_STACK];  // array of stack items
   int           Top;               // index to top of stack