Review for Midterm

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Review for Midterm

• CS 416 Operating Systems Design

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Midterm Examination

• Date October 27th (Wednesday)
• Time 6.30 PM to 9.00 PM
• Location Same classroom
• Chapters covered 1 to 8
• Closed book, Closed Notes
• Format
• True or false questions
• Short answer questions
• Long questions/problems

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Operating Systems

• Why Operating System?
• What is Operating System?
• For who is OS built?
• Historic Evolution
• Interfaces
• Variety of Operating systems
• Real time, embedded, PC, Server, Cray
• Multiprocessor, distributed,..

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Architecture

• Data and Code Management in Memory
• Instruction Set Architecture
• Invoking the OS. Mechanisms? Differences?
• I/O event notification. Mechanisms?
  Differences?
• Send/receive data to I/O devices. Mechanisms?
  Differences?

5
Processes and Threads

• Stack. Activation records. What is stored
  there?
• Heap. What is stored there?
• Address space. What is it?
• Process context. Thread context. What are they
  comprised of?
• PCB. TCB. Where are they stored? What do they
  store?
• Context switching. How does it happen? Any
  problems?
• User-level and kernel-level threads. Pros and
  cons?

6
Synchronization Deadlock

• Critical section. Locks. Semaphores. Monitors.
• Atomic operations. Examples?
• Deadlock. Necessary conditions? Techniques for
  tackling deadlocks?
• Bankers algorithm.

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CPU Scheduling

• Metrics throughput, utilization, turnaround,
  response time, deadlines
• Preemption.
• Policies FCFS, SJF, RR, Priorities, Feedback.
  Pros and cons.
• Multiprocessor scheduling

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Example Short Questions

• What differentiates a PCB from a TCB, and what
  impact does this difference have on context
  switching?
• What is the purpose of synchronization?
• Give one sentence definition of the function of
  an operating system
• When will SJF algorithm approximates FIFO?

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Previous Midterm Questions 1

• Compare semaphores and monitors. Expressiveness?
• Semaphores are lower level constructs. Scattered
  all over the program. Easy to make mistakes.
  Implemented by a library.
• Monitors are high-level, structured constructs.
  Incorporate data, code, and condition variables.
  Easier programming and fewer mistakes.
  Programming language construct.
• They are equivalent in terms of expressiveness.

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Previous Midterm Questions 2

• Define process states and transitions.
• Running process is being executed by the CPU.
• Ready process is ready to run but is waiting for
  the CPU.
• Blocked process is waiting for a blocking
  operation (e.g. I/O)
• Issue blocking operation running -gt blocked
• Completion of blocking operation blocked -gt
  ready
• Turn of a process to execute ready -gt running
• In time-sharing systems, end of quantum running
  -gt ready

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Previous Midterm Questions 3

• Compare FIFO, SJN, RR, and Priority with Feedback
  for process scheduling. Which one minimizes
  turnaround time?
• FIFO is simplest algorithm, but leads to long
  waiting times. RR eliminates this problem, but
  favors CPU-bound jobs. SJN eliminates problem
  with FIFO, but requires info on job length. PWF
  alleviates problem with FIFO without info on
  length.
• SJN minimizes turnaround time.

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Example Problem Questions

• CPU Scheduling
• Synchronization evaluate solutions, write
  solutions using variety of constructs
• Deadlocks required conditions, prevention,
  avoidance etc.

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HW Problems