System Interactions

The lessons up to this point have explained how you can do some pretty remarkable things. Using their techniques you can read inputs entered by the user, perform intricate calculations, repeat a sequence of commands a huge number of times, and even build your own classes to model complex situations.

All of the programs that you've written so far, however, are self-contained. They get input from the user, but otherwise they don't interact with the computer.

The lessons in this section explain some of the ways a program can interact with the system. They explain how to read and write files, explore the filesystem, and print.

• Lesson 29: Using Files
• Lesson 30: Printing