A thread is a single line of execution within a single application. Nearly all of today's operating systems are multithreaded; that is, your application can have more than one concurrent line of execution at a time. Multithreading is a key way to improve the responsiveness of an application, because most processors today can execute multiple threads in parallel and operating systems are optimized to share resources among multiple threads.

Qt supports multithreading over the host operating system through three key classes:

The first represents a single thread of execution, while the latter two are used to synchronize thread access to data structures.

By design, your application runs entirely on the user thread, a single thread of execution that starts when your application starts. You can create new threads of execution (which cannot manipulate the user interface) by subclassing QThread and overriding the run method. Then, when you need to perform...