List and explain at least two mechanisms by which a parent process communicates information to its child process.

List and explain at least two mechanisms by which threads synchronize with each other.

In what situations can a QTimer be used instead of a QThread? Why would one want to do that?

  A QTimer is useful if the simultaneous task that needs to be performed can be implemented as an incremental algorithm that requires repeated calls to a function that does not run for a long period of time. In this situation, we can avoid the use of threads (which sometimes have problems accessing QObjects/QWidgets from other threads).

What does it mean for an function to be thread-safe?

 A thread-safe function is one that can be called concurrently by multiple threads and is guaranteed to serialize access to shared data, perhaps through the use of a mutex or lock.

Which class can be used in non-GUI threads? QImage or QPixmap?

  QImage can be used in other threads. QPixmap is considered a "gui" class and should only be used in the main GUI thread.

What does it mean for a function to be reentrant?

  Multiple threads can call a reentrant function safely, and they do not need to access the same data, so they do not block each other during the calls.

How do you tell a non-GUI thread to enter into an event loop?

  QThread::exec()

Without using extra threads, how can you keep the GUI responsive while still performing a long-running loop?

  qApp->processEvents()