1. © 2004, D. J. Foreman 1 CS350 Operating Systems

2. © 2004, D. J. Foreman 2 Administrivia  Assignments ■ Homework on most chapters ■ Approximately 8 lab assignments  Exams ■ Midterm ■ Final (comprehensive)  Quizzes ■ Random, 10 minutes each  Grades required to pass (after curving) ■ >= 70 average on labs ■ >= 70 average on (h/w + quizzes) together ■ >= 60 on midterm to pass

3. © 2004, D. J. Foreman 3 Course Outline

4. © 2004, D. J. Foreman 4 Introduction & Motivation  Wanted – a methodology to: ■ get more work done in a fixed time ■ allow multiple users on 1 computer ■ allow programs to interact with each other ■ maximize memory and CPU utilization ■ reduce the need for device handling ■ allow programs' parts to be shared ■ make the system more usable (friendlier?) ■ make system faster

5. © 2004, D. J. Foreman 5 Why Study Operating Systems? Understand support structure so we can: –Exploit system features –Learn to write more effective code Learn to design an OS

6. © 2004, D. J. Foreman 6 What IS an Operating System?  A "virtual machine" that provides: ■ An abstraction of some virtual computer ■ Common functionality for apps ■ Security across apps/devices ■ Some level of concurrency (maybe) ■ Portability across real machines ■ Simplified access to resources ■ Sharing of resources ■ Services for apps

7. © 2004, D. J. Foreman 7 Perspectives  End user ■ Getting work done  Application programmer ■ More efficient use of system ■ Make work easier for user  O/S programmer ■ Exploit h/w ■ Enhance performance, usability

8. © 2004, D. J. Foreman 8 Examples of System Software  Tools- a DBMS  API's- functions to create windows  Resident programs – resource mgmt

9. © 2004, D. J. Foreman 9 Abstractions  User ■ Windows, folders  Application programmer ■ OS, language API's ■ Run-time libraries & DLL's ■ Shell  OS programmer ■ Hardware interfaces ■ Machine instructions ■ OS service interfaces

10. © 2004, D. J. Foreman 10 Abstract View of System User Space O/S Space Application Programming Interface

11. © 2004, D. J. Foreman 11 The API  Application Programming Interface ■ Exposes a portion of an environment ■ Provides services I/O Memory Protection Security

12. © 2004, D. J. Foreman 12 Evolution of OS's  Uni-programming ■ DOS  Apparent multiprogramming ■ Windows Versions 2 to 3.1  True multi-programming ■ UNIX/LINUX, OS/2, Windows95+ ■ Mainframe systems: MVS, VMS, VM  Multithreading (mainstream systems) ■ OS/2 ■ System-V (AIX, Solaris, SCO Unixware) ■ Windows 95/98/NT/XP, 200x ■ Linux

13. © 2004, D. J. Foreman 13 OS Strategies  Batch ■ All work pre-scheduled  Timesharing ■ Multi-user, Interactive  PC's and Workstations ■ Single-user, interactive  Embedded ■ Satellites, robots, etc  PDA's ■ Single-user, interactive, small  Network OS's ■ Multi-machine, multi-user

14. © 2004, D. J. Foreman 14 Resource Management  Resources ■ Memory ■ CPU cycles ■ I/O Includes networks, robot arms, motors That is, any means of getting information (or signals) into or out of the computer

15. © 2004, D. J. Foreman 15 Resource Sharing  Why do we need to share? ■ Greater throughput ■ Lowers cost of resources ■ Allows more resources to be available

16. © 2004, D. J. Foreman 16 The Kernel  Implements O/S functions  Privileged, non-interruptible  Sometimes reduced to a "micro-kernel" ■ Absolutely minimal set of functions required to be in privileged mode ■ Micro-kernel does NOT include : Device drivers File services Process server Virtual memory mgmt