The main Function

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is another single-line comment indicating that program execution begins at the next line.

Line 6

is a part of every C++ program. The parentheses after main indicate that main is a program building block called a function. C++ programs typically consist of one or more functions and classes (as you’ll learn in Chapter 3). Exactly one function in every program must be named main. Figure 2.1 contains only one function. C++ programs begin executing at function main, even if main is not the first function defined in the program. The keyword int to the left of main indicates that main returns an integer value. The complete list of C++ keywords can be found in Fig. 4.2. We’ll say more about return a value when we demonstrate how to create your own functions in Section 3.3. For now, simply include the keyword int to the left of main in each of your programs.

The left brace, {, (line 7) must begin the body of every function. A corresponding right brace, }, (line 11) must end each function’s body.