Two-state Process Management Model
The operating system’s principal responsibility is in controlling the execution of processes. This includes determining the interleaving pattern for execution and allocation of resources to processes. One part of designing an OS is to describe the behaviour that we would like each process to exhibit. The simplest model is based on the fact that a process is either being executed by a processor or it is not. Thus, a process may be considered to be in one of two states, RUNNING or NOT RUNNING. When the operating system creates a new process, that process is initially labeled as NOT RUNNING, and is placed into a queue in the system in the NOT RUNNING state. The process (or some portion of it) then exists in main memory, and it waits in the queue for an opportunity to be executed. After some period of time, the currently RUNNING process will be interrupted, and moved from the RUNNING state to the NOT RUNNING state, making the processor available for a different process. The dispatch portion of the OS will then select, from the queue of NOT RUNNING processes, one of the waiting processes to transfer to the processor. The chosen process is then relabeled from a NOT RUNNING state to a RUNNING state, and its execution is either begun if it is a new process, or is resumed if it is a process which was interrupted at an earlier time.
From this model we can identify some design elements of the OS:
- The need to represent, and keep track of each process.
- The state of a process.
- The queuing of NON RUNNING processes
Read more about this topic: Process Management (computing)
Famous quotes containing the words process, management and/or model:
“Rules and particular inferences alike are justified by being brought into agreement with each other. A rule is amended if it yields an inference we are unwilling to accept; an inference is rejected if it violates a rule we are unwilling to amend. The process of justification is the delicate one of making mutual adjustments between rules and accepted inferences; and in the agreement achieved lies the only justification needed for either.”
—Nelson Goodman (b. 1906)
“No officer should be required or permitted to take part in the management of political organizations, caucuses, conventions, or election campaigns. Their right to vote and to express their views on public questions, either orally or through the press, is not denied, provided it does not interfere with the discharge of their official duties. No assessment for political purposes on officers or subordinates should be allowed.”
—Rutherford Birchard Hayes (1822–1893)
“If the man who paints only the tree, or flower, or other surface he sees before him were an artist, the king of artists would be the photographer. It is for the artist to do something beyond this: in portrait painting to put on canvas something more than the face the model wears for that one day; to paint the man, in short, as well as his features.”
—James Mcneill Whistler (1834–1903)