This section consists of theory questions, covering topics and content covered in lectures and the textbook. 1. There are two competing views of an operating system – that is, operating systems provide services for two different and competing audiences. Name both audiences and describe 2 services an operating system provides for each audience (total of four). [5 marks] 2. When providing mechanisms for Inter-Process Communication (IPC) through message passing there are several issues which must be considered. For each of the following issues describe the options available, and the benefits and disadvantages of each option. Considering both the system and the application programmer level in this discussion. a. Synchronisation b. Buffering c. Message size d. Sending data or sending a reference [4 marks, one for each part] 3. What is required of the wait() and signal() operations in a semaphore to ensure that mutual exclusion is provided? Support your answer. [2 marks] 4. You have been given a logical address space of 128 pages, and each page consists of 1024 words/bytes. This logical address space is mapped onto a physical memory of 64 frames. a. What is the length (in bits) of the logical address? b. What is the length (in bits) of the physical address? [2 marks, one for each part] Section B This section consists of practical questions, assessing your ability to use and apply algorithms and techniques discussed in lectures and the textbook. 5. You are given a list of process below, with arrival times and burst times for all. Answer the following questions using non-preemptive scheduling, based only on the knowledge you have at the time the decision is made. Process Arrival Time Burst Time P1 0.0 7 P2 0.6 2 P3 1.0 1 P4 1.2 2 a. What is the average turnaround time for these processes using FCFS scheduling? b. What is the average turnaround time for these processes with the SJF scheduling algorithm? c. The SJF algorithm should improve performance, but here we see a convoy effect since we did not know that shorter processes were coming. Calculate what the average turnaround time would be if the CPU is left idle for the first 1 unit of time, and then uses SJF. Not that this will increase the waiting time for P1 and P2. We could call this algorithm future-knowledge scheduling. [3 marks, one for each part] 6. Here is a snapshot of a system: