Case Study 6

OPERATING SYSTEMS

Case Study 6

Using the process state diagram, explain why there is no transition:
• From the READY to WAITING.
• From the WAITING to RUNNING.

No transition from READY to WAITING state.

What happens during READY state? During this state, A thread state is ready to run and waiting for scheduler to allot it a processor for running. This process is said to be ready if it is waiting to be assigned to a processor. This state can be reached only from ready state when the scheduler selects it for running.

What happens during WAITING state? Let’s state for example a state thread. A thread state is in waiting state when the thread blocks voluntarily. This state can be reached only from running state. A process is said to be blocked if it is waiting for some event to happen such that as an I/O completion before it can proceed. Note that a process is unable to run until some external event happens.

Reason/s why there is no transition from READY to WAITING state. Logically during the job and process status, an ordered path is followed in order to finish a process or a job wherein an entire job follows a series of steps which corresponds to different processes of the CPU (job scheduling, I/O request handling, interrupt handling, etc.). To sum it up, a READY state cannot proceed to the WAITING state not unless it had undergone through the RUNNING state.

No transition from WAITING to RUNNING state.

What Happens from READY to RUNING state? Ready State to Running State Occurs when all other processes have had their share and it is time for the first process to run again. This is where interrupts are issued. What happens when interrupts are issued? It is where the scheduler decides that the running process has run long enough and it is time to let another process have CPU time.

What happens during RUNNING state to WAITING state? Also called the “blocked state”. When process discovers that the RUNNING state cannot continue. If running process initiates an I/O operation before its allotted time expires, the running process voluntarily relinquishes the CPU.

True to be told, the job and process status follows ordered steps for a job to be done. In that case the RUNNING to WAITING state has transition trough initiation by job instruction while the WAITING state can only proceed to RUNNING state only during when it is time for the delayed job during running to continue the process before going again to RUNNING.