Case 6

Processor Management

Memory management is concerned with managing the computer’s available pool of memory, allocating space to application routines and making sure that they do not interfere with each other. Some operating system routines directly support application programs as they run thus must be resident. Other transient routines are stored on disk and read into memory only when needed. To have a better allocation of jobs into memory, there is also a system that process the jobs as they arrived. This is what we call the processor manager.

            In the processor management, it is subdivided into two submanagers. The job-scheduler that manage and schedule the job processing and the process scheduler that schedules the processes and determines execution of the steps.

            In the processing of the jobs, there comes its five states. The Hold, Ready, Waiting, Running and Finished. These are the job status or the process status.

In this diagram, why is it that there is no transition from the READY to the WAITING ?

When the job enters the system and accepted, it would be place in the HOLD state. When the state changes from HOLD to READY, the job was waiting for the CPU to process it. As we all know, CPU or the central processing unit is the one who fetches instruction, interpret it, fetch data then process it and then write the data. And when the state changes from READY  to RUNNING, the CPU then process the requested job. During the processing of the job, there comes that page fault or interrupts. This thing occurs when the I/O request was not already stored in the memory. So, the state changes from RUNNING to WAITING. And after waiting, the job will now be ready to process and run for processing and then the job will be finished.

There is no transistion from Ready to Waiting since the job that is ready to be processed would never be interrupted. Interruptions only happen when the job is running. That is why we call them interrups because it interfere the processing of a certain job.

And why is it that there is also no transition from WAITING to RUNNING?

            When the state changes from Running to Waiting, it means that a page fault occurs or an I/O is requested during the process. There is no transition from Waiting to Running.  A wait state is a delay which is experienced by a computer processor when accessing external memory or another device. Computer microprocessors are very fast, while memory technology does not seem to be able to catch the processors. On the waiting state, the program would not run directly since it has to be ready first before it processed or wait for an I/O operation to complete, or a resource to become available.