April
1999 QUESTION 4 Total Marks: 20 Marks |
Click here to access other
questions
Click to access
|
(a) | Explain what is meant by inheritance
in object-oriented programming and give one benefit of it.
|
[3] |
Singapore Post requires a program to simulate its postal system. You are to write such a program. | ||
(b) | An item of mail contains a postage cost (an
integer representing cents) and the type of the mail (a pointer to an array of
characters). Give an implementation of the class Mail that contains: (1) these private data items; (2) an accessor for the postage
cost; and (3) a method display that
prints the mail and the postage cost in the form $x.xx, e.g. the cost 100 would be
displayed as $1.00.
|
[5] |
(c) | A package is an item of mail that has postage
$3.50 and a integer weight. Use inheritance to implement the class Package that contains a constructor that takes a
weight and initialises all its variables appropriately.
|
[6] |
(d) | A mailbox is a collection of mail items.
Consider the following declaration of the class Mailbox. class MailBox { Give the implementation of a function total_postage that takes a reference to a mailbox and returns the total postage of all mail items in it. |
[6] |