11、What are the two main functions of an operating system? 12、What is the biggest advantage of implementing threads in u

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11、What are the two main functions of an operating system?
12、What is the biggest advantage of implementing threads in user space? What is the biggest disadvantage?
13、What is the difference between a physical address and a virtual address?
14、Some operating systems provide a system call rename to give a file a new name. Is there any difference at all between using this call to rename a file and just copying the file to a new file with the new name, followed by deleting the old one?
15、Confidentiality, integrity, and availability are three components of security. Describe an application that integrity and availability but not confidentiality, an application that requires confidentiality and integrity but not (high) availability, and an application that requires confidentiality, integrity, and availability