COS 318: Operating SystemsIntroductionJaswinder Pal SinghComputer Science DepartmentPrinceton University(http://www.cs.princeton.edu/courses/cs318/)2Today!Course Staff and Logistics!What is an operating system?!Evolution of computing and operating systems!Why study operating systems?!What’s in COS 318?3Course Staff and Logistics!Instructor"Jaswinder Pal Singh, 423 CS Building, [email protected] hours: 3-5pm Thu!Teaching Assistants"CJ Bell, [email protected] hours: TBA (e.g. 2-4pm Mon and Fri)"Yun Zhang, 223 CS, [email protected] hours: TBA (e.g. 2-4pm Mon and Fri)!Information"Website: http://www.cs.princeton.edu/courses/cos318"Subscribe to [email protected] “TBD”!Precept"Time: ? 8:30-9:30pm Wed"Location will be announced on the website!Design review"? Monday 6-9pm5COS318 in Systems Course Sequence!Prerequisites"COS 217: Introduction to Programming Systems"COS 226: Algorithms and Data Structures! 300-400 courses in systems"COS318: Operating Systems"COS320: Compiler Techniques"COS333: Advanced Programming Techniques"COS432: Information Security"COS471: Computer Architecture!Courses needing COS318"COS 461: Computer Networks "COS 518: Advanced Operating Systems"COS 561: Advanced Computer Networks6Course Materials!Textbook – in U-Store"Modern Operating Systems, 3rd Edition, Andrew S. Tanenbaum"Note: 3rd edition came out in Dec 2007, older versions are dated!Lecture notes"Handout in class and on website!Precept notes"Handout in precepts and on website!Other resources – on website7Exams, Participation and Grading!Grading"First 5 assignments: 50% with extra points"Midterm: 20%"Final project 20%"Reading & participation 10%!Midterm Exam"Tests lecture materials and projects"Tentatively scheduled on Thursday of midterm week!Reading and participation"Signup for each class and hand in your reading notes"Grading (3: excellent, 2: good, 1: poor, 0: none)8The First 5 Assignments!Assignments"Bootup (150-300 lines)"Non-preemptive kernel (200-250 lines)"Preemptive kernel (100-150 lines)"Interprocess communication and driver (300-350 lines)"Virtual memory (300-450 lines)!How"Pair up with a partner, will change after 3 projects"Each project takes two weeks"Design review at the end of week one"All projects due Mondays 11:59pm!The Lab"Linux cluster in 010 Friends Center, a good place to be"You can setup your own Linux PC to do projects9Project Grading!Design Review"A signup sheet for making appointments"10 minutes with the TA in charge"0-5 points for each design review"10% deduction if you miss the appointment!Project completion"10 points for each project"Extra points available!Late policy of grading projects"1 hour: 98.6%, 6 hours: 92%, 1 day: 71.7%"3 days: 36.8%, 7 days: 9.7%10Final Project!A simple file system!Grading: 20 points!Do it alone!Due on Dean’s date (get approx. 3 weeks)11Things To Do!Do not to put your code or designs or thoughts on the Web"Other schools are using similar projects"Not even on facebook or the like!Follow Honor System: ask when unsure, cooperation OK but work is your own (or in pairs for programs)!For today’s material:"Read MOS 1.1-1.3!For next time"Read MOS 1.4-1.5!Email me the information on the next slideEmail to [email protected]!Name!Year!Major!E-mail address!Phone #!Picture via URL (optional, but helps me learn names)!Why you’re taking the class!What you’d like/hope to learn1213Today!Course Staff and Logistics!What is an operating system?!Evolution of computing and operating systems!Why study operating systems?!What’s in COS 318?14What Is an Operating System?!Software that sits between applications and hardware"(Also between different applications, and between different users, see later)!Provides services and interfaces to applications!Has privileged access to hardwareUser applications call OS routines for this access and for the servicesHardwareOperating SystemvigccBrowser DVD Player15What Does an Operating System Do?!Provides a layer of abstraction for hardware resources"Allows user programs to deal with higher-level, simpler and more portable concepts than the vagaries of raw hardware• E.g. files rather than disk blocks"Makes finite resources seem infinite!Manages these resources"Manages complex resources and their interactions for an application"Allows multiple applications to share resources without hurting one another"Allows multiple users to share resources without hurting one anotherAbstraction!Hiding underlying details, and providing cleaner, easier-to-use, more elegant concepts and interfaces instead"Also provides standardized interfaces despite diversity of implementation underneath!A key principle in Computer Science!A key to understanding Operating Systems16Example of Abstraction: Disk!Disk hardware and operation are very complex"Multiple heads, cylinders, sectors, segments, each with different fininte sizes"Have to wait for physical movement before actually writing or reading data to/from disk"Data stored discontiguously for performance and reliability"To even read or write simple data would take a lot of coordination when dealing with hardware directly"Sizes and speeds are different on different computers!OS provides simple read() and write() calls as the application programmer’s interface (API)"Manages all the complexity transparently in conjunction with the disk controller hardware17Example of Abstraction: Networks!Data communicated from one computer to another are:"Broken into fragments that are sent separately and arrive at different times and out of order"Waited for and assembled at the destination"Sometimes lost, so fragments have to be resent"An application programmer does not want to manage this!OS provides a simple send() and recv() interface"Takes care of all the complexity, in conjunction with networking hardware18Resource Management!Allocation!Virtualization!Reclamation!Protection19Resource Allocation!Computer has finite resources!Different applications and users compete for them!OS dynamically manages which applications get how many resources!Multiplex resources in space and in time"Example of time multiplexing?"Example of space multiplexing?!E.g. what if multiple applications run infinite loops? while (1);20Resource Virtualization!OS gives each program the illusion of effectively infinite, private resources"“infinite” memory (by backing up to disk)"CPU (by time-sharing)21Resource Reclamation!The OS giveth, and the OS taketh