Threads

A thread is an independent and parallel part of a process.

Each thread has its own:

However, unlike a process, threads share:

with the other member threads in the process.

Threads are handled at a higher level than processes, and can be switched without involvement of the operating system kernel.

If this is the case, thread switching is very rapid and efficient. such threads are known as user-level threads.

Threads are especially important for the development of event-driven programs.

Topology

A thread can be through of as a lightweight process.

Threads are created within a normal process.

Independent tasks can be split from the main process into individual threads.

Ease of Programming (modularity)
- Many applications need to perform several distinct tasks simultaneously. Much easier to create one separate thread per task, than to attempt to do them all within one linear program.
Responsiveness
- In a multi-threaded interactive application a program may be able to continue executing, even if part of it is blocked.
  - In a web browser: user waiting for image to download, but can still interact with another part of the page.
Resource Sharing
- Threads share memory and resources of the process they belong to, thus we have several threads all within the same address space.
Economy
- Threads are more economical to create and context switch as they share the resources of the processes to which they belong.
Utilisation of Parallel Architectures
- In a multiprocessor architecture, where each thread may be running in parallel on a different processor, the benefits of multi-threading can be increased.