Creating Reusable Code (C++)
Now that we have learned how to use the Visual Studio IDE and how to create command-line and Windows applications, we will learn how to write code so that it can be used by multiple applications. One way to do this is to create a library that contains related classes and algorithms. For example, Visual C++ is included with many libraries that any C or C++ application can use, such as the C Run-Time Library and the Standard C++ Library. Without these libraries, there would be no standard way for a C or C++ application to write to the console or determine the current date and time.
Every C or C++ application will likely use one of the previously mentioned libraries. You can also create your own libraries of classes and algorithms that any application can use. With Visual C++, you can create three kinds of libraries:
Dynamic link libraries (DLLs).
In general, if you are creating a library that can be used by native C++ code, you will create either a dynamic link library or a static library. For more information about how to determine which type of library to create, see DLLs. If you are creating a library that can be used by C++/CLI or any other .NET language such as C# or Visual Basic, you will create a managed assembly.
In this section, we will create a simple library of standard math operations such as addition and multiplication, and we will show how applications can use this library.