What are process states?

A process is a program in execution that consists of more than just program code (text section). This concept works under all operating systems because every task performed by the operating system requires a process to execute.

A process executes by changing its state over time. The state of a process is defined by the current activity and status of that process within the system.

Types of Process States

Each process may be in any one of the following five states −

• New − The process is being created and initialized by the operating system.

• Ready − The process is loaded in memory and waiting to be assigned to a processor for execution.

• Running − The process is currently executing instructions on the CPU.

• Waiting (Blocked) − The process is waiting for an event to occur, such as I/O operation completion or receiving a signal.

• Terminated − The process has finished execution and is being removed from the system.

It is important to understand that only one process can be running on any processor core at any given instant, while many processes may be in the ready or waiting states simultaneously.

Process State Diagram

State Transitions Explained

Step 1 − When a new process is created, it starts in the New state and is then admitted to the Ready state once system resources are allocated.

Step 2 − The scheduler dispatches a ready process to the Running state when the CPU becomes available.

Step 3 − A running process can be preempted and moved back to the Ready state if a higher priority process arrives or its time slice expires.

Step 4 − When a running process requests I/O or waits for an event, it moves to the Waiting state. Once the I/O operation completes or the event occurs, the process returns to the Ready state.

Step 5 − When a process completes execution, it moves from the Running state to the Terminated state, where system resources are deallocated.

Key Points

• Process states help the operating system manage multiple processes efficiently

• State transitions are controlled by the process scheduler and system events

• Understanding process states is crucial for CPU scheduling algorithms

• The waiting state prevents CPU cycles from being wasted on blocked processes

Conclusion

Process states represent the different phases a process goes through during its lifetime in the system. The five-state model (New, Ready, Running, Waiting, Terminated) provides a framework for efficient process management and CPU scheduling in modern operating systems.