C++ Primer Plus

To compile multiple source files, you just list them all in the command line:

g++ my.cxx precious.cxx

This produces an executable file called a.out and two object code files, my.o and precious.o. If you subsequently modify just one of the source code files, say my.cxx, you can recompile by using my.cxx and the precious.o:

g++ my.cxx precious.o

The GNU compiler is available for many platforms, including the command-line mode for Windows-based PCs as well as for Unix systems on a variety of platforms.

Command-Line Compilers for Windows Command Prompt Mode

An inexpensive route for compiling C++ programs on a Windows PC is to download a free command-line compiler that runs in Windows Command Prompt mode, which opens an MS-DOS-like window. Free Windows downloads that include the GNU C++ compiler are Cygwin and MinGW; they use g++ as the compiler name.

To use the g++ compiler, you first open a command prompt window. Cygwin and MinGW do this for you automatically when you start those programs. To compile a source code file named great.cpp, you type the following command at the prompt:

g++ great.cpp

If the program compiles successfully, the resultant executable file is named a.exe.

Windows Compilers

Windows products are too abundant and too often revised to make it reasonable to describe them all individually. At the present the most popular is Microsoft Visual C++ 2010, which is available in the free Microsoft Visual C++ 2010 Express edition. The Wikipedia link (http://en.wikipedia.org/wiki/List_of_compilers) provides a comprehensive list of compilers for many platforms, including Windows. Despite different designs and goals, most Windows-based C++ compilers share some common features.

Typically, you must create a project for a program and add to the project the file or files constituting the program. Each vendor supplies an IDE with menu options and, possibly, automated assistance, in creating a project. One very important matter you have to establish is the kind of program you’re creating. Typically, the compiler offers many choices, such as a Windows application, an MFC Windows application, a dynamic link library, an ActiveX control, a DOS or character-mode executable, a static library, or a console application. Some of these may be available in both 64-bit and 32-bit versions.

Because the programs in this book are generic, you should avoid choices that require platform-specific code, such as Windows applications. Instead, you want to run in a character-based mode. The choice depends on the compiler. In general, you should look to see if there is an option labeled Console, character-mode, or DOS executable and try that. For instance, in Microsoft Visual C++ 2010, select the Win32 Console Application option, click Application Settings, and select the Empty Project option. In C++Builder XE, select Console Application under C++Builder Projects.

After you have the project set up, you have to compile and link your program. The IDE typically gives you several choices, such as Compile, Build, Make, Build All, Link, Execute, Run, and Debug (but not necessarily all these choices in the same IDE!):

• Compile typically means compile the code in the file that is currently open.

• Build or Make typically means compile the code for all the source code files in the project. This is often an incremental process. That is, if the project has three files, and you change just one, and then just that one is recompiled.

• Build All typically means compile all the source code files from scratch.

• As described earlier, Link means combine the compiled source code with the necessary library code.

• Run or Execute means run the program. Typically, if you have not yet done the earlier steps, Run does them before trying to run a program.

• Debug means run the program with the option of going through step-by-step.

• A compiler may offer the option of Debug and Release versions. The former contains extra code that increases the program size, slows program execution, but enables detailed debugging features.

A compiler generates an error message when you violate a language rule and identifies the line that has the problem. Unfortunately, when you are new to a language, you may find it difficult to understand the message. Sometimes the actual error may occur before the identified line, and sometimes a single error generates a chain of error messages.

Tip

When fixing errors, fix the first error first. If you can’t find it on the line identified as the line with the error, check the preceding line.