| The three principal states that have been described | | | | from the Suspended queue, or it honors a new |
| (Ready, Running, Blocked) provide a systematic way | | | | process request. Execution then continues with the |
| of modeling the behavior processes and guide the | | | | newly arrived process or management. |
| implementation of the operating system. Many | | | | Swapping is an I/O operation. It enhances |
| operating systems are constructed using these three | | | | performance. When all the processes in main memory |
| states. | | | | are in the Blocked state, the operating system can |
| There is good justification for adding a additional | | | | suspended one process by putting it in the |
| states to the model. Consider a system that does | | | | Suspended state and transferring it to disk. The |
| not employ virtual memory. Each process to be | | | | space that is freed up in the memory can then be |
| executed must be fully loaded into main memory. All | | | | used to bring in another process. |
| the process in all the queues must be resident in main | | | | When the operating system has performed a |
| memory. | | | | swapping out operation, it has two choices for |
| The reason for all this elaborate machinery is that I/O | | | | selecting process to bring into main memory. It can |
| activities are much slower than computation, and | | | | admit a newly created process, or it can bring in a |
| therefore the processor in a uni programming system | | | | previously suspended process. It would appear that |
| is idle most of the time. Memory holds multiple | | | | the preference should be to bring in a previously |
| processors and that the processor can move to | | | | suspended process to provide it with service rather |
| another process when one process is waiting. But the | | | | than increasing the total load on the system. |
| processor is so much faster than I/O that it will be | | | | Quick Note: Taking the Nonsense out of looking for |
| common for all the process in memory to be waiting | | | | the right spyware remover |
| for I/O. Thus, even with multiprogramming, a | | | | If you really want to take the work out of looking |
| processor could be idle most of the time. | | | | for that right Spyware Protection from a Spybot go |
| Swapping involves moving part or all of a process | | | | to the Internet and get a Free Spybot or a Free |
| from main memory to disk. When none of the | | | | Spybot Search and Destroy |
| processes in main memory is in the Ready state, the | | | | Download, In order to prevent your vital information |
| operating swaps one of the Blocked processes out | | | | from being ripped from your computer get your |
| onto disk into a Suspended Queue. This is a Queue | | | | Spybot Remover Today. |
| of existing processes that have been temporarily | | | | All the processes that have been suspended are in |
| kicked out of main memory, or suspended. The | | | | the blocked state at the time of suspension. |
| operating system then brings in another process | | | | |