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Computer Systems II Gordon College

Computer Systems II Gordon College. Operating System Overview. Class Intro. Operating System Class Two Directions: Practical Linux+ Guide to Linux Certification and Lab Manual Lab Experience Theoretical Operating Systems (3rd Edition Gary Nutt) Lecture and Projects.

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Computer Systems II Gordon College

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  1. Computer Systems IIGordon College Operating System Overview

  2. Class Intro • Operating System Class • Two Directions: • Practical • Linux+ Guide to Linux Certification and Lab Manual • Lab Experience • Theoretical • Operating Systems (3rd Edition Gary Nutt) • Lecture and Projects

  3. Why Study Operating Systems? • Understand the model of operation • Easier to see how to use the system • Enables you to write efficient code • Learn to design an OS • Even so, OS is pure overhead of real work • Application programs have the real value to person who buys the computer

  4. Perspectives of the Computer print open() start-printer cut malloc() read-disk send fork() save track-mouse Application Software Application Software Application Software System Software System Software System Software Hardware Hardware Hardware (c) OS Programmer View • End User • View (b) Application Programmer View

  5. System Software • Independent of individual applications, but common to all of them • Examples • C library functions • A window system • A database management system • Resource management functions • The OS

  6. Using the System Software Application Programmer Software API Command Line Interpreter Loader Window System Libraries Libraries Libraries Compiler System Software OS Database Management System Hardware

  7. Application Software, System Software, and the OS Human-Computer Interface Application Software API System Software (More Abstract Resources) OS Interface Trusted OS (Abstract Resources) Software-Hardware Interface Hardware Resources

  8. The OS as Resource Manager • Process: An executing program • Resource: Anything that is needed for a process to run • Memory • Space on a disk • The CPU • “An OS creates resource abstractions” • “An OS manages resource sharing”

  9. write(char *block, int len, int device, int track, int sector) { ... load(block, length, device); seek(device, 236); out(device, 9); ... } write(char *block, int len, int device,int addr); fprintf(fileID, “%d”, datum); Resource Abstraction load(block, length, device); seek(device, 236); out(device, 9)

  10. Disk Abstractions Application Programmer OS Programmer int fprintf(…) { ... write(…) … } void write() { load(…); seek(…) out(…) } load(…); seek(…); out(…); (c) fprintf() abstraction (a) Direct Control (b) write() abstraction

  11. Abstract Resources User Interface Application Abstract Resources (API) Middleware OS Resources (OS Interface) OS Hardware Resources

  12. Abstract Machines Abstract Machines Idea Program Result Physical Machine Idea Program Result … … … Idea Program Result

  13. Resource Sharing • Space- vs time-multiplexed sharing • To control sharing, must be able to isolate resources • OS usually provides mechanism to isolate, then selectively allows sharing • How to isolate resources • How to be sure that sharing is acceptable • Concurrency

  14. The OS as a Conductor The OS coordinates the sharing and use of all the components in the computer

  15. Multiprogramming Abstract Machine Pj Abstract Machine Pi Abstract Machine Pk … OS Resource Sharing Pi Memory Pk Memory … Pj Memory Time-multiplexed Physical Processor Space-multiplexed Physical Memory

  16. Multiprogramming(2) • Technique for sharing the CPU among runnable processes • Process may be blocked on I/O • Process may be blocked waiting for other resource, including the CPU • While one process is blocked, another might be able to run • Multiprogramming OS accomplishes CPU sharing “automatically” – scheduling • Reduces time to run all processes

  17. How Multiprogramming Works Process 1 Process 2 Process 3 Time-multiplexed CPU Process 4 Space-multiplexed Memory

  18. Speeding Up the Car Wash Vacuum Inside Wash Dry (a) The Sequential Car Wash Vacuum Inside Wash Dry (b) The Parallel Car Wash

  19. Multiprogramming Performance Pi’s Total Execution Time, ti Time 0 ti (a) Pi’s Use of Machine Resources P1 P2 … Pi … PN Time (a) All Processes’ Use of Machine Resources Using the processor I/O operation

  20. OS Strategies • Batch processing • Timesharing • Personal computer & workstations • Process control & real-time • Network • Distributed • Small computers

  21. Batch Processing Job 3 Job 19 Input Spooler Output Spooler Output Spool Input Spool

  22. Batch Processing(2) • Uses multiprogramming • Job (file of OS commands) prepared offline • Batch of jobs given to OS at one time • OS processes jobs one-after-the-other • No human-computer interaction • OS optimizes resource utilization • Batch processing (as an option) still used today

  23. A Shell Script Batch File cc -g -c menu.c cc -g -o driver driver.c menu.o driver < test_data > test_out lpr -PthePrinter test_out tar cvf driver_test.tar menu.c driver.c test_data test_out uuencode driver_test.tar driver_test.tar >driver_test.encode

  24. Timesharing Systems Abstract Machines Result Physical Machine Command Result Command … Result Command

  25. Timesharing Systems(2) Computer Research Corp ‘67 • Uses multiprogramming • Support interactive computing model (Illusion of multiple consoles) • Different scheduling & memory allocation strategies than batch • Tends to propagate processes • Considerable attention to resource isolation (security & protection) • Tend to optimize response time

  26. Personal Computers • CPU sharing among one person’s processes • Power of computing for personal tasks • Graphics • Multimedia • Trend toward very small OS • OS focus on resource abstraction • Rapidly evolved to “personal multitasking” systems

  27. Process Control & Real-Time • Computer is dedicated to a single purpose • Classic embedded system • Must respond to external stimuli in fixed time • Continuous media popularizing real-time techniques • An area of growing interest

  28. Networks • LAN (Local Area Network) evolution • 3Mbps (1975)  10 Mbps (1980)  100 Mbps (1990)  1 Gbps (2000) • High speed communication means new way to do computing • Shared files • Shared memory • Shared procedures/objects • ???

  29. Distributed OS • Wave of the future App App App App App App Distributed OS Multiple Computers connected by a Network

  30. Small Computers • PDAs, STBs, embedded systems became commercially significant • Have an OS, but • Not general purpose • Limited hardware resources • Different kinds of devices • Touch screen, no keyboard • Graffiti • Evolving & leading to new class of Oses • PalmOS, Pocket PC (WinCE), VxWorks, …

  31. Evolution of Modern OS Timesharing Network OS Memory Mgmt PC & Wkstation Client-Server Model Scheduling Batch Protection Protocols System software Real-Time Human-Computer Interface Memory Mgmt Protection Scheduling Scheduling Files Devices Small Computer Network storage, Resource management Modern OS

  32. Examples of Modern OS • UNIX variants (e.g. Linux) -- have evolved since 1970 • Windows NT/2K -- has evolved since 1989 (much more modern than UNIX • Win2K = WinNT, V5 • Research OSes – still evolving … • Small computer OSes – still evolving …

  33. The Microsoft OS Family Win32 API Win32 API Subset Win32 API SubSet Windows CE (Pocket PC) Windows 95/98/Me Windows NT/2000/XP

  34. Summary • An Operating System must be able to: • provide functionality to apps • provide abstraction of hardware to users and apps • provide the sharing of resources to processes • provide security and protection • be as transparent as possible • be as light as possible

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