What are the four principal approaches of multi threading?

The four principal approaches to multithreading are:

1. Thread-based Multithreading: This approach involves creating multiple threads within a single process, allowing concurrent execution and better resource sharing.
2. Process-based Multithreading: In this method, multiple processes run independently, each potentially containing its threads, which helps achieve parallelism but can lead to higher overhead.
3. Event-driven Multithreading: This approach uses events or messages to trigger thread execution, allowing a program to remain responsive while performing tasks asynchronously.
4. Fork-Join Multithreading: This model divides a task into subtasks (forking), processes them in parallel, and then combines the results (joining), optimizing resource use and execution time.