Operating Systems

1. In Von Neumann architecture, a typical instruction execution cycle includes four steps, fetch instruction, store instruction, decode instruction, and execute instruction. 2. The two primary purposes of an operating system are to manage the resources of the computer and to provide a convenient interface to the hardware for programmers 3. When the CPU is in kernel mode, the CPU is prevented from accessing areas of memory that are not owned by the current process. 4. Multiprogramming allows operating system to keep several processes in memory simultaneously, which keeps either the CPU or the I/O devices busy at all time. 5. Threads that are part of the same process share the stack of the process, that means they do not have their own stacks. 6. With kernel-level threads, multiple threads from the same process can be scheduled on multiple CPUs simultaneously. 7. The scheduler is the part of an Operating System that selects the process to be dispatched to the CPU from the ready queue. 8. A Shortest Remaining Time First scheduler cannot preempt a currently running longer job. 9. The longer the time slice, the more a Round Robin scheduler gives similar results to a First Come First Served scheduler. 10. Shortest Remaining Time First is the best preemptive scheduling algorithm that can be implemented in an Operating System