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Wherefore OS?

HW & Systems: Operating Systems IS 101Y/CMSC 101 Computational Thinking and Design Tuesday, October 22, 2013 Marie desJardins University of Maryland, Baltimore County. Wherefore OS?. A “ naked machine” has no tools or programs to help the user Write instructions in binary

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Wherefore OS?

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  1. HW & Systems:Operating SystemsIS 101Y/CMSC 101Computational Thinking and DesignTuesday, October 22, 2013Marie desJardinsUniversity of Maryland, Baltimore County

  2. Wherefore OS? • A “naked machine”has no tools or programs to help the user • Write instructions in binary • Write data in binary • Load instructions into memory one cell at a time • Initiate program run • Too difficult for humans to do • We must build an interface to hide the details and make the computer easier to build • The OS is an abstraction of the machine that keeps users and programmers from having to think about the low-level hardware details

  3. Virtual Machine (abstraction!) Naked machine: • Write program in binary • Load instructions one-by-one into memory • Insert start into memory address 0 and push “go” button • Read results from memory one-by-one, in binary Virtual machine: • Write program using text editor in high-level language • Save program to folder • Use translator to convert to binary • Use scheduler to load and run • Use I/O system to print results

  4. UnQuiz • What is the kernel? What are its main functions? • What is the difference between a program, a process, and a thread? • What is multitasking? • When does the kernel interrupt a running process? • What is a context switch?

  5. UnQuiz Part Two • What are some possible process scheduling policies? • What do these different ways of measuring CPU efficiency mean? • CPU utilization • Average latency • Throughput • Fairness • What is virtual memory?

  6. Deadlock • Safe use of resources: ensure that computer doesn’t get stuck in deadlock • Multiple programs requesting access to resources • Deadlock occurs when all programs have some resources, and are waiting for resources held by others • Deadlock prevention: if you can’t get all resources, release all you have and try again later • Deadlock recovery: if no acknowledgement, send message again

  7. Midterm Review Any grade change requests must be made in writing, with a clear explanation of the error (e.g., addition or transcription problem) or reason for regrade (e.g., an explanation of why you think your answer was a reasonable one or should have received more partial credit) “Another student got grade X” is not a justification for a grade change unless you can clearly explain why your answer deserves that grade

  8. Guest LectureDr. Chuck LaBergeComputer Engineering

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