As described in the introduction, in this book we will work on how to convert an application to follow the MVVM pattern. The example application is a POS client for purchasing clothes. The first version will use an approach that mixes the user interface and the model of the application (the business logic). This type of design is referred as monolithic and it is pretty much what you have when you deal with so-called legacy code, especially if your application was created in the 1980s and 1990s.
Note
You come across monolithic design in old applications (legacy) but you can also end up with such a structure if you ...
