The Process State Diagram
Using the process state diagram, explain why there is no transition:
· From the READY to WAITING.
· From the WAITING to RUNNING.
Firstly, I’ve just seen a video presentation of the process of job handling in an operating system in a website. As I have observed in job handling, when we start any valid form of application programs, the High Level Scheduler of an Operating System loads entire or just a part of the code’s program from a secondary storage into memory. Then, it construct a structure of data in memory called a process control block that will be apply to hold information of the process, such as its current status and where in memory it is located. When a new process is created, it is given a unique process identification number and a new record is created for it in the process table which includes the address of the process control block in memory.
Dealing with the question “explain why there is no transition from the ready to waiting”, in the ready state of this diagram, only one job must be placed in the ready state at any one time after the job leaves the hold state. In the process state diagram, processes entering the system must be initialized into the ready state first before entering to other states. If a job or a process will enter the waiting state from ready state, it is impossible to have a job that has not yet entered the running state to have a moment of testing the job’s status if it has any interrupts or I/O requests that are needed to be in the waiting state. So therefore, any jobs that have entered the ready state must be initialized first in the running state. It has no transitions to be made if the job is from the ready state and goes to the waiting state. According to the rule, jobs that has I/O or interrupts must be placed in a waiting state before it goes back to the ready state.
On the other hand, the question “why there is no transition from waiting to running” can be answer according to these explanations. First of all, only one process or job can be in the running state at any one time. . The remaining processes will either be ready or blocked, and for each of these states there will be a queue of processes waiting for some event. The lines connecting the process state diagram represent possible transitions from one state to another. Processes entering the system must initially go into the ready state. A process can only enter the running state from the ready state. There would be no transition that would occur when any job transfers from waiting to running.
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