Name:
Sec: 11/01/2005
Lab 4.1 Defining and Using Classes
Recall that two structured data types are arrays,
which have elements of the same type, and structures, which have elements of
differing types. Another structured data type is a class, which is specifically
designed to combine data and functions in a single unit. A class is a
collection of a fixed number of components. The components of a class are
called the members of the class. If a member of a class is a variable, you
define it just like any other variable, but you cannot initialize it at
definition. If a member of a class is a function, you typically use the
function prototype to define that member. Member functions can directly access
any data member of the class without passing that data member as an argument.
No memory is allocated in a class definition.
Instead, memory is allocated when the class is instantiated (an object is created).
Additionally, the semicolon (;) is part of the syntax. The members of a class
are classified into three categories: private, public, and protected. By
default, all members of a class are private. Private members cannot be accessed
outside of the class. A public member is accessible outside the class.
Protected members will be discussed in Chapter 13.
A class and its members can be described
graphically using Unified Modeling Language (UML) notation. A UML diagram
contains three boxes stacked vertically. The top box contains the name of the
class; the middle box contains the data members and their data types; and the
bottom box contains the member method names, parameter list, and return types.
The + (plus) sign indicates that it is a public member; the - (minus) sign
indicates that it is a private member. The # (pound) symbol indicates that it
is a protected member.
Objectives
In this lab, you define a class and declare
objects.
After completing this lab, you will be able
to:
Use basic
UML notation to design and specify a class.
Write a
driver program that contains a class definition.
Instantiate
an object of a class.
Practice
using coding projects and working with a program defined across multiple files.
Describing Classes Using the
Unified Modeling Language (UML) Notation and Declaring Objects
1a. Create a
UML diagram for a struct named Money that will
contain data members. Your struct (or
class) should contain a char data member named type
and a double data member named amount as public
members. (See Ch #12, pg. 599 for a
quick discussion and example of UML diagrams).
1b. Implement
the struct in your diagram in C++ and save your code in a file named Money.h.
2a. Create a
UML diagram for a class named Exchange that will
contain data members and member functions to allow a user to input, validate,
and convert pesos, Euro dollars, and Swiss francs to
The class
has 2 data members, US
and entered, which will be of
the type Money that you defined in
Exercise 7, and should be private members.
The
Boolean function getData and the void
functions convert and displayExchange
have no formal parameters and should be public members.
The void
function outputType has no
formal parameters and is a private member.
2b. Implement the design and member functions of
your diagram in C++ and save your code in 2 files. One file named Exchange.h
should contain the definition of your Exchange class. The other file, named Exchange.cpp, should contain the implementation of the function
members of the Exchange class. You will
need to #include “Money.h” in your Exchange.h file. Likewise you will need a #include “Exchange.h” at the top of your Exchange.cpp file.
2c. Implement
the member functions so that they meet the following criteria:
The
member function named getData should prompt the user for
the type of currency: (p) for Mexican pesos, (d) for U. S. dollars, (f) for
Swiss francs, (e) for Euro dollars, and (q) for quit, and then input the
character into the data member entered.type. If a
‘q’ is entered, the value false is returned. If a valid character is entered,
the program prompts the user for an amount, and inputs that amount into the
data member entered.amount. Use a
loop in the function until the user enters q to quit or enters a valid type.
The
member function named displayExchange displays
the type of currency and the beginning amount and the amount in
The
member function named outputType displays
a description for the character type of currency; for example,‘d’would display
“U. S. dollars”.
The
member function named convert assigns the exchange
amount of the value entered in U. S. dollars to US.amount
and assigns the character type of entered.type
to US.type. The conversions are: 1
U. S. dollar = 0.9553 Euro dollars = 1.4054 Swiss francs = 9.815 Mexican pesos
2d. Since you are now writing a program that
contains multiple files (3 so far, Money.h,
Exchange.h and Exchange.cpp) you MUST begin using projects in your IDE (Dev or
Visual C++ compilers). If you haven’t
already, create a new project in your development environment (ConvertMoney
would be a good name for the project).
Add the 3 files you have created so far to your project.
3a. Now we will create what is known as a driver
program that will use and test your Exchange class. Design a driver program that #include “Exchange.h” the Exchange class
that you created in step 2. Name the
program TestExchange.cpp (and add it
to your project). This file will contain
your main function for the program you are writing. Write a loop that creates an Exchange object
and uses the getData() member. The loop
should continue until the returned value from getData() is false. After calling getData(), within the loop you
should then call the member functions convert() and displayExchange().
3b. Enter, compile, link, and execute TestExchange.cpp.
The following is a copy of the screen results that
might appear after running your program, depending on the data entered. The
input entered by the user is shown in bold.
This program prompts the user to enter
a character to designate the type of
currency to be exchanged and the amount
of money
to be exchanged.
Enter a character for currency type and
an amount.
(P)esos, Swiss (f)rancs, (E)uro dollars
or (q)uit: x 123.543
You entered an invalid type, please
re-enter.
p 123.543
You entered 123.54 in Pesos, which is
$12.59 in U.S. dollars.
Enter a character for currency type and
an amount.
(P)esos, Swiss (f)francs, (E)uro dollars
or (q)uit: f 500
You entered 500.00 in Swiss francs,
which is $355.77 in U.S. dollars.
Enter a character for currency type and
an amount.
(P)esos, Swiss (f)francs, (E)uro dollars
or (q)uit: e 987
You entered 987.00 in Euro dollars,
which is $1033.18 in U.S. dollars.
Enter a character for currency type and
an amount.
(P)esos, Swiss (f)francs, (E)uro dollars
or (q)uit: q
Lab 4 Finished
You have now completed Lab 4.
Turn in the previous pages to the instructor and make sure you have
uploaded your TestExchange.cpp, Exchange.h, Exchange.cpp and Money.h in a new Lab4 folder in
your online student account.
Attached at the end of this lab is a description
of your third programming assignment, which will be due next Friday Oct 21. After completing this lab, now is a good time
to begin thinking about how you will implement the second programming
assignment.