Introduction to Operating Systems: Concepts and Overview

1. Operating SystemsCSE 411 Introduction and Overview Sept. 5 2006 - Lecture 1 Instructor: Bhuvan Urgaonkar

2. About Me • Bhuvan Urgaonkar • Ph.D., Sept. 2005, Univ. of Mass. Amherst • Research areas • Operating systems, Distributed systems, Computer networks • Office hours: Thu 5-7 PM, or by appointment • Office: 338D, IST Building • Email: bhuvan @ cse Welcome!

3. Administrative Stuff

4. Teaching Assistants • Yuan Fang • Office hours: M 10-11 AM, W 11.30-12.30 PM, 346D • Email: yufang @ cse • Arjun R. Nath • Office hours: Tue 5-7 PM • Email: anath @ cse

5. Online Resources andText-book • Course Web page: • http://www.cse.psu.edu/~bhuvan/teaching/fall06/411/411.html • All material will be available via ANGEL • Please seek help from the TAs if needed • Textbook • Operating Systems Concepts, 7th ed. Silberschatz, Galvin, and Gagne

6. Course Mailing List • Via ANGEL • Use with care • I will send a test email, please respond to my email address if you don’t receive it by Friday • Welcome to write to me or the TAs • Make sure to include “411” in the subject

7. Grading • Quizzes (approx. one per week): 15% • Written home-works (5): 15% • Projects (3): 35% • Exams (3): 35% • 90+: A, 75-89: (A, B], 65-74: (B, C], … • Subject to change; will not make it stricter • No relative grading - relax :)

8. Grading • Projects will be done in groups of 2 • One group of size 3 will be allowed if needed • If your partner drops the course … • 2 Exams, each on a different subset of the material; final exam comprehensive • Late policy: • Strict deadlines for quizzes and home-works • Loss @ 20% per extra day for projects • Inform TAs well in advance if there is a real reason for a delay in project submission • Same for conflict exams

9. Grading • Projects • 50% grade on how functional your project is • The other 50% on your write-up and presentation • We will give instructions on what we expect when we make the projects available • Quizzes: • Online on ANGEL • Multiple-choice, mostly

10. Computing Resources • Solaris or Linux accounts for projects • Email me or the TAs if you don’t have an account or have any doubts/problems

11. Academic Honesty • Do all assignments on your own • Quizzes, home-works, projects • We will use software to compare project source codes • Both partners on each team are expected to know everything about each project

12. Assumed Background • First course on algorithms and data structures • Comfortable programming in C/C++ • Comfortable with a debugger like gdb • Preliminary understanding of computer architecture • We will cover some basics in this course • Talk to me if you have doubts • Background quiz to be turned in by next Monday

13. Before We Begin … • Some advice • Speak up in class, ask questions • Attend all classes • Hint: Ideas concerning homeworks, exam questions, … • Do all assignments on your own! • Make good use of office hours • Bring printouts to class and take notes on them • Read text-book soon after class • Sections to read will be made available on the Web site alongside lecture notes • Even better: read before class and ask questions

14. Operating Systems: Introduction & Background

15. What is an Operating System (OS)? • Literal meaning • Software that helps operate a computer • Lack of consensus on the term operate • Overloaded term • Software that runs on a computer when nothing else is running (e.g., right after it boots up => kernel) • Very restrictive, what about dynamically loaded device drivers? • Windows = Any other OS + Windows Media Player + … • Very inclusive, why not everything else in the world?

16. What is an OS • There is no single truth here • Our OS somewhere between these extremes • Definition using negation • Applications • Moving the burden to defining an application :) • OS = all software minus applications • Helps the applications use the computer • Helps manage the resources of the computer

17. Why do we need an OS? • Why not provide this functionality in hardware? • Why this separate piece of software?

18. A Little Bit of History

19. The Dark Ages (1940s - 60s) Hardware: expensive; humans: cheap • Evolution of functionality • Single user • Batch processing • Overlap of I/O and computation • Multi-programming

20. 1. Single User • One user at a time on console • Computer executes one function at a time • No overlap: computation & I/O • User must be at console to debug Multiple users => inefficient use of machine

21. 2. Batch Processing • Execute multiple “jobs” in batch: • Load program • Run • Print results, dump machine state • Repeat • Users submit jobs (on cards or tape) • Human schedules jobs • A program loads & runs jobs • The Operating System More efficient use of machine, complicates debugging

22. 3. Overlap I/O and Computation • Before: machine waits for I/O to complete • New approach: more work by the OS • Allow CPU to execute while waiting • Add buffering • Data fills “buffer” and then output • and interrupt handling • I/O events trigger a signal (“interrupt”) More efficient use of machine, but still one job at a time

23. 4. Multiprogramming • Allow several programs to run at same time • Run one job until I/O • Run another job, etc. • OS manages interaction between programs: • Which jobs to start • Protects program’s memory from others • Decides which to resume when CPU available

24. So what does an OS do? • Two kinds of functionality • Management of computer resources • Sharing CPU between tasks • Memory management • Certain services to users • Load programs, run them

25. OS Complexity • Increased functionality & complexity • First OS failures • Multics (GE & MIT):announced 1963, released 1969 • OS/360 released with 1000 known bugs • Need to treat OS design scientifically • Managing complexity becomes key to…

26. The Renaissance (1970s) Hardware: cheap; humans: expensive • Users share system via terminals • The UNIX era • Multics: • army of programmers, six years • UNIX: • three guys, two years • “Shell”: composable commands • No distinction between programs & data • But: response time& thrashing

27. The Industrial Revolution (1980s) Hardware very cheap; humans expensive • Widespread use of PCs • IBM PC: 1981, Macintosh: 1984 • Simple OS (DOS, MacOS) • No multiprogramming, concurrency, memory protection, virtual memory, … • Later: networking, file-sharing, remote printing… • GUI added to OS (“WIMP”)

28. The Modern Era (1990s-now) Hardware cheap; processing demands increasing • “Real” operating systems on PCs • NT (1991); Mac OS X; Linux • Different modalities: • Parallel: Multiple processors, one machine • Distributed: Multiple networked processors • Real-time: Strict or loose deadlines • Sensor networks: Many small computers

29. OSes Today • Active research area (so I like to believe!) • Top CS conferences, several distinguished researchers/groups • Intersects with theory/algos., software engg., architecture, distrib. comp. • Major market presence • Microsoft, Apple, HP, … • New environments, new devices • Web, P2P systems, Internet apps, sensor networks, mobile devices, multimedia, … • New challenges • Distributed systems, heterogeneous devices, ubiquitous computing, utility computing, mobile computing, autonomic computing

30. Outline of this Course

31. Course Outline • Resource Management (and some services an OS provides to programmers) • CPU management • Memory management • I/O management (emphasis: Disk) • Cross-cutting design considerations and techniques • Quality-of-service/fairness, monitoring, accounting, caching, software design methodology, security and isolation • Advanced topics • Distributed systems • Data centers, multi-media systems, real-time systems, virtual machines

32. Next Time • Background on Computer Architecture