Operating Systems Question

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Question 1 (a) An operating system hides complicated details of the computer from its users and makes it much easier to use through well-defined interfaces. Describe and discuss examples of OS user interfaces. (b) The concept of interrupts is an essential part of modern operating systems and hardware. A keyboard, when connected to a computer, raises an interrupt whenever there is a key press. Explain the interrupt process in this example, in terms of both software and hardware (c) Memory management is a crucial aspect of operating system functionality. A problem that needs to be addressed is that of memory fragmentation. Explain with examples how both internal and external memory fragmentation occur. (d) Consider the following bitmap, where shaded boxes represent allocated memory, and un-shaded boxes represent available memory: 1 23 456 7 8 9 10 11 12 13 14 15 16 17 18 Assume two memory allocation requests are processed by the system: firstly the system is asked to allocate 4 blocks of memory for process A. After this is successful, the system is asked to allocate two blocks of memory for another process B. State which blocks from the above bitmap would be allocated to which process when using the Best Fit memory allocation algorithm. (i) (i) State which blocks from the above bitmap would be allocated to which process when using the Worst Fit memory allocation algorithm. (e) Page replacement happens when a requested page is not in memory, .e. when there is a page fault. Let us assume that we have three frames, i.e. three pages can be in memory at any one time, and consider the sequence of page references: 9, 0, 1, 2, 0, 3, 0,4 (i) llustrate and state how many page faults would be caused by the given replacement algorithm and the Least-Recently-Used page replacement algorithm respectively. () Compare the First-In-First-Out algorithm and Least-Recently-Used algorithm