6.1. Introduction

In this chapter, we discuss functions, beginning with an overview of a portion of the C++ Standard Library’s math functions. Next, you’ll learn how to declare a function with more than one parameter. We’ll also present additional information about function prototypes and how the compiler uses them to convert the type of an argument in a function call to the type specified in a function’s parameter list, if necessary.

Next, we’ll take a brief diversion into simulation techniques with random number generation and develop a version of a popular casino dice game that uses most of the C++ capabilities we’ve discussed.

We then present storage-class specifiers and scope rules. These determine the period during which an object exists in memory and where its identifier can be referenced in a program. You’ll learn how C++ keeps track of which function is currently executing, how parameters and other local variables of functions are maintained in memory and how a function knows where to return after it completes execution. We discuss topics that help improve program performance—inline functions that can eliminate the overhead of a function call and reference parameters that can be used to pass large data items to functions efficiently.

Many of the applications you develop will have more than one function of the same name. This technique, called function overloading, is used to implement functions that perform similar tasks for arguments of different types or possibly for different numbers of arguments. We consider function templates—a mechanism for defining a family of overloaded functions. The chapter concludes with a discussion of recursive functions—functions that call themselves, either directly, or indirectly through other functions.