King Saud University - College of Computers and Information Sciences Operating Systems Thursday- February 20, 2014 CSC 227 Homework 1: (A Sample Answer) Spring 2013/2014 Points: 40 Due: Thursday- February 27, 2014(2:00 pm) 1. [6.0 points]Describe in details three main activities of an operating system in regard to: a. memory management. b. process management. 2. [3.0 points] Discuss whether the virtual memory and the time sharing need to be supported by the operating system for a handheld devices or not. For handheld systems, the operating system needs to provide virtual memory, but does not need to provide time-sharing. 3. [4.0 points] Identify three main advantages and one disadvantage of using multiprocessor systems. Answer: Multiprocessors can save money by not duplicating power supplies, housings, and peripherals. They can execute programs more quickly and can have increased reliability. They are also more complex in both hardware and software than uniprocessor systems. 4. [3.0 points] Explain how does the CPU know when the memory operations are complete. When the device is finished with its operation, it interrupts the CPU to indicate the completion of the operation. 5. [4.0 points=1.0+3.0] What is interrupt handler? Give some examples of different interrupt. Answer: An interrupt handler is summoned to deal with the cause of the interrupt; control is then returned to the interrupted context and instruction. 6. [6.0 points]What are the main differences of network, parallel and distributed operating systems? Answer: a. Network: Provides operating system features across a network such as file sharing. b. Distributed: This system distributes computation among several physical processors. The processors do not share memory or a clock. Instead, each processor has its own local memory. They communicate with each other through various communication lines, such as a high-speed bus or local area network. c. Parallel: Used in systems where there are multiple CPU’s each running the same copy of the operating system. Communication takes place across the system bus. 7. [4.0 points]Why dual mode operation is important for operating systems? Answer: A means of protection to ensure proper execution of operating system. This protection is achieved by marking some instructions as privileged and not allowing them to execute in user mode. 8. [10.0 points] Explain in details Figure 1.5 of textbook.