This chapter is from the book
Q&A
Q. Can one function contain a call to another function?
A. Most definitely; in fact, such calls can be nested as deeply as you need them to be.
Q. What characters can I use in function names?
A. Function names must start with a letter or an underscore and can contain letters, digits, and underscores in any combination. They cannot contain spaces, punctuation, or other special characters.