Explain Process state transition diagram in brief.

A process state transition diagram is a graphical representation of all possible states that a process can have, and the transitions between those states. The states are represented by circles, and the transitions are represented by arrows.

1. New: The process is being created.

2. Ready: The process is waiting to be assigned to a processor. Ready processes are waiting to have the processor allocated to them so they can run.

3. Running: Instructions are being executed. Once the process has been assigned to a processor by the scheduler, the process state is set to running and the processor executes its instructions.

4. Waiting: The process is waiting for some event to occur(such as an I/O operation). If a process needs to wait for a resource (like waiting for user input or file to open), then it is moved to the waiting state.

5. Terminated or Exit: The process has finished execution.

In the diagram, each arrow represents a transition from one state to another, such as from 'Ready' to 'Running'. The event causing the transition is labeled along the arrow. For example, a 'Scheduler dispatch' event causes a transition from 'Ready' to 'Running'. Similarly, an 'Interrupt' event causes a transition from 'Running' to 'Ready'.