Flow:

1. Process enters the system, placed in a job queue.
2. Processes residing in the main memory ready and waiting to be executed are kept in the ready queue.
3. Once in a running state, the process can be interrupted, put on wait, or exited.

Process States

A state is the current activity of that process.

Each process may be in one of the following states:

New - The process is being created.

Ready - The process is waiting to be assigned to a processor.

Running - When instructions are being executed.

Waiting - The process is waiting for some event to occur. (Such as I/O completion or signal reception)

Terminated - The process has finished execution.

Process Transitions:

• New → Ready: Upon completion of initialization.
• Ready → Running: Scheduled by the CPU.
• Running → Waiting: Needs resources or I/O.
• Running → Terminated: Completes execution or exits.
• Waiting → Ready: Required resource becomes available.
• Running → Ready: Preempted by scheduler.

Zombie Process

A zombie process, also known as a defunct process, is a process that has completed execution but still has an entry in the process table. This happens when a child process has finished its execution, but its parent process hasn't yet read its exit status.

• They're usually cleaned up when the parent process calls wait() to read the child's exit status.
• If a parent process terminates without calling wait(), the zombie process is adopted by the init process, which periodically cleans up zombie processes.

They're identified by the 'Z' state in process status outputs.