CPSC 457 Operating Systems Midterm Review: Practical Questions

Q1 Describe the steps that occur when a user program to executes a system call (assuming that there is a system library to wrap the call). CPSC 457 - Tyson Kendon 2016

Q2 Describe the steps that occur when the operating system performs a context switch between processes. CPSC 457 - Tyson Kendon 2016

Q3 Consider the following table of process, all of which are available at the time of scheduling and arrived in the order in which they are numbered , with the given burst times and priorities (lower numbers are higher priority). Process Burst Time Priority P1 8ms 2 P2 4ms 1 P3 10ms P4 2ms P5 CPSC 457 - Tyson Kendon 2016

Q3 Draw the Gantt chart and calculate the average turnaround time for the following algorithms. 3a) First Come, First Served 3b) Shortest Job First 3c) Priority 3d) Round Robin (with a 5ms time quantum) CPSC 457 - Tyson Kendon 2016

Q4 Consider the following table of process, with the given burst and arrival times Process Burst Time Arrival Time P1 8ms 0 ms P2 4ms 4 ms P3 10ms 6 ms P4 2ms 12 ms P5 18 ms CPSC 457 - Tyson Kendon 2016

4a) Shortest Job First (Non-Preemptive) Draw the Gantt chart and calculate the average turnaround time for the following algorithms. 4a) Shortest Job First (Non-Preemptive) 4b) Shortest Job First (Preemptive) 4c) Round Robin (with a 5ms time quantum) 4d) A Multi-Level Feedback Queue with 3 queues, a high priority queue served with Round Robin with a a 2 ms quantum, a medium priority queue served with Round Robin with a a 6 ms quantum, a low priority queue served First Come First Served. a job is preempted if a higher priority job is available. A preempted job is put on the HEAD of its queue. CPSC 457 - Tyson Kendon 2016

Q5 5) Recall the formula calculating exponential average: ♣️n+1 = ♥️tn + (1 - ♥️) ♣️n For a process with the following real burst times, an initial estimated burst time of (4 ms) and a memory factor () of .5 calculate estimated burst times for each n. (Round to the nearest integer ms)   1 2 3 4 Estimated Burst 5ms Real Burst 10ms 2ms 8ms 3ms 12ms CPSC 457 - Tyson Kendon 2016