CSCI 201 Lab 12 -- Parameters and Classes in C++

Getting ready

Download a ZIP'ed copy of the Lab 12 project and store it in the C:\files directory. Use PowerZip to extract the archive to the C:\ directory.

This should create C:\files\lab12\ with two subdirectories called SwapEm and Stoplite.

Parameter passing

Rather than running the program, step through it with the debugger. Press F10 to move one statement at a time through the main routine. When the yellow arrow reaches the call to SwapEm, press F11 to move into the SwapEm routine. Then contine to press F10 to move through the statements of SwapEm.

As you step through the program, pay attention to the variables window at the bottom off your Visual C++ window. At first, it will display variables of main

but, as your move into SwapEm, it displays variables of SwapEm.

The information displayed in a variables window is the contents of C++ function activation records.

Step to the statement FormArg2 = Temp

Now move your mouse into the variables and move between the activation records of main and SwapEm. You do this selecting from a pull-down menu that is displayed when you click on the down arrow at the right end of the textbox labeled Context.

Instructor Checkoff I

Classes

This time you'll see two windows. One window is our stoplights from Lab 11. The North-South light should be a solid green, while the East-West light is a blinking red. Right now the second window is nothing more than a magenta background. Now press within the magenta. A car should appear! This car will remain until the East-West light is green for at least fifty Tick's.

The only files you'll change in this lab are stoplite.h and stoplite.cpp. If you'll look very carefully, you'll notice a slight difference between the Lab 11 stoplite.cpp and this one. The difference is in the Tick routine which now takes a single argument called carPresent. The variable carPresent represents a car "pad" on the East-West road. It is non-zero when a car is present, and it is zero when no car is present.

Instructor checkoff II

Modify the StopLight class so that the EW light will stop flashing when the car arrives.

Instructor checkoff III

Modify the StopLight class so that the NS light will change to Caution 20 ticks after the car arrives at the EW light.

Instructor checkoff IV

Modify the StopLight class so that the NS light will change to Caution 20 ticks after the car arrives at the EW light and then to Stop 20 ticks later when the EW light changes to Go.

Instructor checkoff V

Modify the StopLight class so that it will go through a complete single cycle each time an East-West car arrives and allow each car to cross the intersection 40 ticks after it arrives at the light. You must hold the green light in the East-West direction for at least fifty Tick's to allow the East-West car to pass.