process

A major difference between a process and a thread is that each process has its own address space, while a thread does not require a new address space to be created.

All threads in a process can access its shared memory. Threads also share other OS dependent resources such as processors, files, and network connections. As a result, the management overhead for threads is typically less than for processes. Threads, however, are not protected against each other and must carefully synchronize when accessing the shared process resources to avoid conflicts.

Terminated: When a process completes its execution or when it is being explicitly killed, it changes to the "terminated" state. The underlying program is no longer executing, but the process remains in the process table as a "zombie process". When it is finally removed from the process table, its lifetime ends.

Running: The OS has selected the process for execution and the instructions within the process are executed on one or more of the available CPU cores.

Ready suspended: A process that was initially in ready state but has been swapped out of main memory and placed onto external storage is said to be in suspend ready state. The process will transition back to ready state whenever it is moved to main memory again.

Blocked: A process that is blocked is one that is waiting for an event (such as a system resource becoming available) or the completion of an I/O operation.

Blocked suspended: A process that is blocked may also be swapped out of main memory. It may be swapped back in again under the same conditions as a "ready suspended" process. In such a case, the process will move to the blocked state, and may still be waiting for a resource to become available.