Middleweight Thread

Modern OS kernels are considered middleweight threads because multiple threads can exist in a single address space. This reduces the amount of context that needs to be saved for each one, significantly decreasing the switching time. In contrast, a Unix process is considered a heavyweight thread. Most user-level threads are considered lightweight threads.

A thread and a task are very similar and are often confused. The OS considers a running program a task, giving each task a turn at performing an operation. If a program requests that a file be saved, the OS creates a thread. Most of today’s operating systems support multitasking and multithreading to provide efficient application processing.