Exercises 2.3, 2.4

What are the main sub-systems involved in exercise 2.7?

Why do we say that the system engineering process is a waterfall process?

Make a research on the web and post a description (an references) in 5 lines maximum of a software error that resulted in a economical/human disaster (Hint: Ariane 5, ATT 1990...) Do not forget also to look at the references given in the book.