Chapter 1, “Anatomy of a C Program,” introduced functions, the building blocks of C programs. In this chapter, you'll learn how to use functions in C programs.
We begin by discussing some function basics, including the role of the main function. We then show you how to call functions, pass data to them, return data from them, and declare them. The chapter concludes with a brief look at old-style function declarations, which you may encounter in some programs.