Computer Operating Systems

Problem #1

Describe CPU burst and CPU-VO burst cycle. Describe the basic process scheduling disciplines: Shortest Job First (SJF), Shortest Remaining Time (SRT), Round-Robin (RR), First Come First Served (FCFS).

Assume the processes become runnable as follows: Arrival time, ms Burst time, ms

Assume the time slice for RR is 1 ms. Drawn Gantt charts of scheduling the processes by the four scheduling

disciplines. Explain your answer.

Problem #2

Explain the need and principle of page-based memory organization. Explain the concepts of page and frame. Differentiate between physical and logical address. Explain page number and offset. Describe how page table translates a logical address into a physical address.

Explain the need for multilevel page table and how this translation happens in such a table. Draw a diagram to illustrate your answer.

Problem #3

Explain why operating system schedules disk read-write head movement. Consider a 1000- cylinder disk and the following queue of requests:

30,180,350,600,950

Assume that the read-write head is presently at the cylinder number 500 going from outer (higher numbered) to inner (lower numbered) cylinders. Describe shortest-seek-time-first (SSTF), LOOK, and C-LOOK would schedule the read-write head movement. Explain your

answer. Out of these three scheduling algorithms, which one would most likely be implemented in practice? Explain.