For the tutorials in this chapter, you will take as your starting point a Time for action tutorial you did in Chapter 2 that involves updating a file with news about examinations. You are responsible for collecting the results of an annual examination where writing, reading, speaking, and listening skills are evaluated. The professors grade the examinations of their students in the scale 0-100 for each skill, and generate text files with the information. Then they send the files to you for integrating the results in a global list.
In the initial chapters, you were learning the basics of PDI. You were worried about how to do simple stuff such as reading a file or doing simple calculations. In this chapter, you will go beyond that and take care of the details such as making a decision if the filename expected as a command line is not provided or if it doesn't exist.