The nested DO loop can be a killer for many people. Often it is difficult to see why variables change the way they do, and why the output is the way it is. Hopefully this example will help step you through the process slowly and easily enough to explain all of the subtle nuances of the process. In the example below, a program has been laid out for you. By clicking in the area provided, a pointer will move to show you what line you are on. A message will appear at the bottom explaining the process, and the variables and output will show you what the current values are.
Click in the white space below each time you are ready for the computer to take another step in the process. Or click on the "ALL" button for the process to continue at a steady rate for you.
Please let me know if there are any ways to make this example clearer.