CS 354 EXAM STUDY GUIDE QUESTIONS WITH CORRECTLY SOLVED ANSWERS(GUARANTEED PASS)

CS 354 EXAM STUDY GUIDE QUESTIONS WITH CORRECTLY
SOLVED ANSWERS: GUARANTEED PASS



1) Name the sections of memory -- Answer ✔✔ Stack, Shared Libs, Heap, Bss, Data,
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Text

2) What goes in the text section of memory? -- Answer ✔✔ Instructions that the
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program runs t




3) Name the four features of a 3rd generation machine -- Answer ✔✔ Processor,
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memory system, I/O devices, interrupts t t t t




4) Are virtual or physical addresses cached? -- Answer ✔✔ Virtual addresses
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5) What is the purpose of the interrupt mask? -- Answer ✔✔ It is a bitmask kept in the
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CPU status register to determine which interrupts are permitted
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6) In XINU, how are processes implemented? -- Answer ✔✔ Each process is a thread of
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the main program
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7) In XINU, is the stack or heap shared? -- Answer ✔✔ The heap is shared, but each
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process has its own stack t t t t




8) Threads within a process share these three things (and a 4th in XINU)... -- Answer
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✔✔ text, data, and bss (and heap)
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9) Where is information about each process stored? -- Answer ✔✔ In the process table
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(or thread table)
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10) A process that is delayed for a specified time is in what state? -- Answer ✔✔ Sleeping
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, 11) A process that is not permitted to execute is in what state? -- Answer ✔✔ Suspended
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12) Where are processes that are ready to execute stored? -- Answer ✔✔ In the
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readylist

13) What is XINU's scheduling policy? -- Answer ✔✔ Highest priority process gets the
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CPU

14) When is the scheduling invariant enforced? -- Answer ✔✔ When the set of eligible
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processes changes, or the priority of any eligible process changes
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15) What function swaps the currently running process? -- Answer ✔✔ ctxsw
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16) Why must ctxsw be written in assembly? -- Answer ✔✔ ctxsw has to save registers,
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which is not possible in C
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17) Which process executes the context switch code? -- Answer ✔✔ The old process
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executes the first half of the context switch, then the new process continues
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executing where previously suspended t t t




18) Which program executes if all user processes are idle? -- Answer ✔✔ The null
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process

19) How does a process end? -- Answer ✔✔ kill
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20) Name an advantage of a mutex implementation over test-and-set -- Answer ✔✔
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Mutex implementations avoid busy waiting
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21) No operating system function should contain code to explicitly ____ interrupts --
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Answer ✔✔ enable t t




22) How can blocking interrupts break the scheduling invariant? -- Answer ✔✔ A high-
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priority process may finish its I/O and be ready to run, but disabling interrupts
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prevents a context switch t t t