Qt is a truly cross-platform framework for building applications. As such, it has a large number of core classes to manage data as well as wrappers around platform services such as threading, the filesystem, network I/O, and of course, graphics.

In this chapter, we discuss some of Qt's core classes that you will find especially handy while writing your applications. In this discussion, we will focus on the bits of Qt that are especially helpful when constructing the business logic for your application. We will begin with a discussion on a handful of useful data classes. After that, we will look at Qt's support for multithreading, a key tool in keeping applications feeling responsive. Next, we will look at file and HTTP I/O, an important component in many applications. We will close with a look at Qt's XML parser, which you can use to create networked applications or use to load XML data from the filesystem.

We will cover the following topics in this chapter: