1) Which of the following instructions should be privileged? (10 points) 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. g. Switch from user to kernel mode. g and time-sharing environmen t, several users share the system simultaneously 2) In a multiprogrammin This situation can result in various security problems. a. What are two such problems? b. Can we ensure the same degree of security in a time-shared machine as in a dedicated machine? Explain your answer. (20 points) 3) Direct memory access is used for high-speed I/O devices in order to avoid increasing the CPU's execution load. a. How does the CPU interface with the device to coordinate the transfer? b. How does the CPU know when the memory operations are complete? c. The CPU is allowed to execute other programs while the DMA controller is transferring data. Does this process interfere with the execution of the user programs? If so, describe what forms of interference are caused(20 points) Amdahl's Law, calculate the speedup gain of an application that has a 60 percent parallel 4) Using component for (a) two processing cores and (b) four processing cores. (10 points) 5) Consider the following code segment: pid t pid; pid = fork(); if (pid-= 0) { /* child process */ fork0; thread create( ...); fork0: a. How many unique processes are created? b. How many unique threads are created? (10 points)