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Unformatted text preview: as a rudimentary form of protection (security) system? 1.8 Which of the following instructions should be privileged? a. Set value of timer. b. Read the clock. c. Clear memory. d. Issue a trap instruction. e. Turn off interrupts. f. Modify entries in device-status table. 1 2 Chapter 1 Introduction g. Switch from user to kernel mode. h. Access I/O device. 1.9 Some early computers protected the operating system by placing it in a memory partition that could not be modiFed by either the user job or the operating system itself. Describe two difFculties that you think could arise with such a scheme. 1.10 Some CPUs provide for more than two modes of operation. What are two possible uses of these multiple modes? 1.11 Timers could be used to compute the current time. Provide a short de-scription of how this could be accomplished. 1.12 Is the Internet a LAN or a WAN?...
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- Winter '09
- Operating Systems, a. Set value, f. Modify entries, Introduction Practice Exercises, h. Access I/O