Why is the only function in the previous example called main? The simple answer is that the code won’t compile if it isn’t! However, it might be more useful to explain how the language works.

A normal C++ application contains many functions (and also many classes, as is discussed in Chapter 2). How does the compiler know which function should be called first? Obviously, you can’t allow the compiler to just randomly choose a function. The rule is that the compiler always generates code that looks for a function named main. If you omit the main function, the compiler reports an error and doesn’t create a finished executable application.

So, the compiler will expect a function named main. Is that all there is to it? Well, not quite. There are some additional items, such as the return type and parameters being correct, but in the case of main, some of the C++ rules are relaxed. In particular, main can take parameters that represent the command-line arguments, but you can omit them if you don’t want to use the command line.

A C++ keyword (also called a reserved word) is a word that means something to the compiler. The keywords used in the example application are using, namespace, and return. You’re not allowed to use these keywords as variable or function names; the compiler will report an error if you do. You’ll find that Visual Studio helps you identify keywords by displaying them in a special color.

An identifier is any name that the programmer uses to represent variables and functions. An identifier must start with a letter and must contain only letters, numbers, or underscores. The following are legal C++ identifiers:

The following are not legal C++ identifiers:

Outside of these restrictions, any identifier will work. However, some choices are not recommended, such as the following:

Before you can create an application, you must write something. Visual Studio 2012 provides an integrated C++ editor, complete with color syntax highlighting and Microsoft IntelliSense to show function parameter information and provide word completion.

The C++/CLI compiler is the tool for converting text source files into something that can be executed by a computer processor. The compiler takes your source files (which usually have a .cpp extension) and builds them into either a stand-alone executable file (with a .exe extension) or a library file to be used in other projects (with a .dll extension).

After you have successfully built the application, you need to run it and test it.

For many development environments, running and testing is often the most difficult part of the application development cycle. However, Visual Studio 2012 has yet another ace up its sleeve: the integrated debugger. The debugger has a rich set of features with which you can easily perform run-time debugging, such as setting breakpoints and variable watches.

The first task is to create a new project for the “Hello, World” program.

The wizard creates a project for you with all the files needed for a simple console application. It also opens the main source file in the editor that contains just the code we want.

Notice that the keywords automatically appear in blue (provided that you spell them correctly).

There are a few things in the automatically generated source code that we don’t need, so let’s remove them. This will give you some practice in using the editor as well as making the code easier to understand. The application is not going to receive any command-line arguments when you run it, so remove everything between the opening and closing parentheses following main—in this example, array<System::String ^> ^args. In addition, the “L” before the “Hello World” string isn’t necessary either (for reasons that I’ll explain later), so you can remove that, as well.

The next step is to build the executable. The term build in Visual Studio 2012 refers to compiling and linking the application. Visual Studio compiles any source files that have changed since the last build and—if no compile errors were generated—performs a link.

To build the executable, on the Build menu, click Build Solution or press F7.

An Output window opens near the bottom of the Visual Studio window, showing the build progress. If no errors are encountered, the message Build: 1 succeeded, 0 failed, 0 up-to-date, 0 skipped will appear in the Output window. If this window is closed, you can open it by selecting Output from the View menu.

If any problems occur, the Error List window will contain a list of errors and warnings.

You can double-click the error line in the Error List window to place the cursor at the line in the source file where the compiler encountered the error. Fix the error (you might have misspelled a keyword or forgotten a semicolon) and rebuild the project. If the Error List pane is closed, you can open it by selecting Error List from the View menu.

After you’ve eliminated all errors and you’ve successfully built the project, you can finally execute the application. On the Debug menu, click Start Without Debugging to run the application. You can also press Ctrl+F5 to execute the application.

You’ll see the output of your application, with the message “Press any key to continue” at the bottom of the output. This line is added by the IDE so that the console window doesn’t simply disappear when the application has finished running.