don't understand this code..

[joevenzon]

Here's a pretty good introduction to templates (specifically see the section on Class Templates):
http://www.cplusplus.com/doc/tutorial/templates.html

In the car.h file you'll see CARDYNAMICS <double> dynamics, which means that for all of the car classes "double" gets substituted for T. I did it this way in case I wanted to try using a 32-bit float instead of a 64-bit double.