COP 4610 Computer Operating Systems Summer 2011 Name:______________________________ Midterm Last 5 digits of ZN: Zxxx __________ This is a CLOSED books/notes test. You are NOT allowed to consult any material you have brought into the classroom. NO exchange of information is allowed among students. Write your name and ZN on each sheet detached. 1.Which of the following instructions should be privileged? Circle the correct answer for each one. (16 pts.) a)Set value of timer yes / no b)Read the Clock yes / no c)Clear memory yes / no d)Issue a trap instruction yes / no e)Turn off interrupts yes / no f)Modify entries in device-status table yes / no g)Switch from user to kernel mode yes / no h)Access I/O device yes / no 2.What is a virtual machine? What are the advantages and disadvantages of it? (12 pts.)
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