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This lecture from Dr. Chuck LaBerge at the University of Maryland, Baltimore County, explores the fundamental concepts of operating systems. It addresses how naked machines function without user-friendly interfaces, requiring binary instructions for operation. The session outlines the role of operating systems as an abstraction layer that simplifies programming, facilitates multitasking, and manages resources effectively. Key topics include the kernel's functions, process scheduling, virtual memory, and deadlock prevention and recovery strategies, enhancing students' computational thinking and design skills.
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HW & Systems:Operating SystemsIS 101Y/CMSC 101Computational Thinking and DesignTuesday, October 22, 2013Marie desJardinsUniversity of Maryland, Baltimore County
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
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
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?
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?
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
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
