The stack in the upper-left corner of the program window displays a list of currently active methods. The name of the currently executing method appears at the bottom of this list, the name of the method that called it is just above, and so forth. For example, if method main called sort_list, which called move_smallest_to_front, which called move_element, the call stack would be:
sort_list
move_smallest_to_front
move_element
Additional methods may be listed above main. These methods are either part of CodeWarrior or part of the operating system. Normally you will be interested only in the ones from main down.
You can view the source code and local variables of any method in the call stack by selecting its name.