Processes, Tasks, and Threads

Processes, Tasks, and Threads are programs or parts of programs underexecution. A program does not define a process, task, or thread since the samecode may underlay different processes, tasks, or threads. At any given time, thestate of a process, task, or thread includes the location of the instruction beingexecuted and the value stored in all memory locations accessible to the program.An important characteristic of processes, tasks, and threads is that they mustexecute their instructions at a speed greater than zero when they are not explicitlyblocked by synchronization operations.

Although the notion of process, tasks, and threads differs across systems, typically a process may contain multiple threads, and threads share memory while processes communicate via messages.