Windows NT Systems Programming: Spring 2000

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Assignment 4: Flying the Spaceship

NOTE: You must do at least one of Assignment 4 or 5. If you do both you will receive extra credit that can be applied towards your grade on the first three assignments. To give you time to consider your options, I am making the due date the same for both assignments but advise you not to wait till the end to do these assignments.

Description: You are to make a small change in the ATL version of the SpaceShip server program demonstrated in class and found here and demonstrate its use by accessing it from a visual basic program. The modifications to the SpaceShip object handle a finite fuel supply. As the spaceship flys it uses fuel as a function of its velocity. When it runs out of fuel, it will stop. You must refuel it before you can move again.

Due: April 20

FUNCTIONAL REQUIREMENTS:

COM Server

1. Add a Fuel Capacity property to the Space Ship
2. When the space ship is out of fuel, it will stop.
3. When flying, decrease the fuel capacity in proportion to the speed.
4. Add a method to refuel which takes as an argument the amount of fuel (up to the capacity of the fuel tank)

COM Client

Write a set of Visual Basic functions in EXCEL that will do the following:

1. LOAD: Load the COM object
2. FLY: Fly the spaceship using a velocity found in an EXCEL spreadsheet cell and updating the current position in a second EXCEL spreadsheet cell
3. REFUEL: refuels the spaceship using an amoutn found in a third EXCEL spreadsheet cell.
4. UNLOAD: unloads the COM object

On an EXCEL spreadsheet which will be used to control the spaceship:

1. Add a button for loading and unloading the COM object
2. Add a button for flying the spaceship which when pressed will update the current position based on the velocity in the velocity cell.
3. Add a button which will refuel the space ship.

IMPLEMENTATION (NON-FUNCTIONAL) REQUIREMENTS:

1. You must build the server using ATL (if fact you will modify the existing ATL program)
2. You must use Visual Basic in Excel.

HINTS:

• You need to change the following line in "MySpaceShip.h" to

  COM_INTERFACE_ENTRY2(IDispatch, IMotion)

• You need to enable macros to enable Visual Basic programming
• You need to declare the COM object to be global so it is accessible from all the VB functions using the following statement at the beginning

  Dim SpaceShipObj As Object

• You can add buttons to an EXCEL spreadsheet by selecting "view/toolbars/forms" and on the resulting toolbar selecting a button control. It will ask you to assign a macro and list the VB functions you wrote - select the one you want. Also edit the button label.
• When changing the value of an EXCEL cell (e.g. velocity), you need to hit the "Enter" key before you can push a button.

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Last updated: March 30, 2000.