Introduction

Purpose: A control system for a multi-disk CD/DVD changer.

Abbreviations, Acronyms:

CD	Compact Disc
DVD	Digital Video Disc and/or Digital Versatile Disc

Background

About the System: You have been hired to implement the control system for a multi-disk CD/DVD changer. The changer has multiple slots, each of which can hold a single disc. Users have access to only one slot at a time. To move between slots, the changer has two buttons, labeled next and previous. The slots in the changer are arranged in a circle so that the user can continuously cycle through them by pressing these buttons.

The changer also has buttons labeled:

eject: Ejects the disc from the currently selected slot (if it has a disc in it).

ejectAll: Ejects the discs from all slots (starting with the currently selected slot)

getID: Gets the ID number (an integer that is greater than or equal to 1) of the disc in the currently selected slot

loadDisc: Loads a disc into the currently selected slot

off: Turns the power off

on: Turns the power on

Existing Components

A Driver has already been implemented. The source code is available but must not be modified.

Driver.cpp

New Components

You must develop the following new components:

Slot ( Design )

DiscChanger ( Design )

Some Advice:

A Development Strategy: It will be very difficult to debug the two classes at the same time. Hence, you should:

1. Implement the Slot class.
2. Test the Slot class.
3. Implement the DiscChanger class.
4. Test the DiscChanger class.

Running the Driver: There are several things you might want to consider when running the driver:

• The driver is case-sensitive. The valid commands (which correspond to buttons on the physical device) are: "eject", "ejectAll", "getID", "loadDisc" (which then prompts for an integer ID greater than 0), "next", "off", "on", and "previous".
• Running the driver can be very tedious. One way to reduce the tedium is to use input redirection.

  As you know, standard input (e.g., cin) normally comes from the console. You can redirect a file to standard input as follows:

  Driver < filename

  Then you can create a file that contains a sequence of commands and avoid the need to type them over and over. (An example is available on-line at test.txt)

• The driver can be told to be either terse or verbose. When it is being terse it does not print any prompts. When it is being verbose it prompts for commands and ID numbers. This behavior is determined at compile-time using the symbol PROMPT.

  To compile a verbose version, use:

  	g++ -c -DPROMPT=1 Driver.cpp
  	

  To compile a terse version, use:

  	g++ -c -DPROMPT=0 Driver.cpp
  	

  The terse version is particularly useful when used with re-directed input.

• You can terminate the driver by typing the end-of-file character (followed by return/enter) when prompted for a command. (Ctrl-Z in Windows; Ctrl-D in UNIX/LINUX)

Testing: At a minimum, you should test your code to make sure that it properly handles:

1. DiscChanger objects of different sizes (see the discssion of the "Size of the DiscChanger").
2. Loading a disc into a slot that isn't empty.
3. Getting the ID from an empty slot.
4. Arbitrary sequences of "next" and "previous" commands.
5. Commands when the DiscChanger is off.

Some tests are available on-line that might help get you started.

Note: You may have trouble moving your test files between machines with different operatings systems. This is because of the way in which an "end of line" is defined.

Late Submission:For this assignment, if your code does not pass the in-lab tests you will have one opportunity to have your code re-tested during the Professor's office hours on the next class-day after the due date (e.g., the Wednesday immediately after the Monday due date). However, you will incur a penalty of 25% (i.e., you will receive a maximum grade of 75).