Overview

A thread is a part of a program which runs asynchronously, in the background of this program. This means than it's possible to perform long operations (compression, image processing, etc) without halting the whole program and let the user continue to do other things. A thread runs within your program, it's not another process. When the main program exits, all the threads are destroyed. Under PureBasic, threads are simply a procedure which is called asynchronously. The thread runs until the procedure exits.

Examples of places of programs where threads are useful are when you need to be able to handle multiple situations with different response times or which occur at different intervals. In the above paragraph, the response times of image processing and the user interface are quite different (you would want to wait for the image to be processed but always have the user interface to respond).

Note: Threads need to be used carefully because it is possible that you can have multiple access to shared resources (memory, variables, files, etc) and you need to manually ensure that you do run into trouble because of this. For example, it is not safe to modify or write to strings from more than one thread because strings share the same internal memory buffer. If you only ever read from strings while your threads are running then it should be safe.

If you still want to modify strings safely in threads (or any other shared access resource), you need to make sure that only one thread can use strings at a time. To do this you should make use of the synchronisation capabilities of the OS you are running on. It is not safe to simply use a global variable as a flag to indicate that the string buffer (or anything else) is being used. How can you ensure correct synchronisation when modifying this global variable?

Note: Don't use DirectX inside threads (MS Windows limitation)! If you need to display graphics in threads use Images and 2DDrawing instead.

Command Index

CreateThread
KillThread
PauseThread
ResumeThread
ThreadPriority
WaitThread

Example

Thread.pb

Supported OS

Windows, Linux