Operating Systems ( 操作系统原理 )

1. Operating Systems (操作系统原理) • Text book: • Dinosaur book （恐龙书） • 操作系统概念 (中译本) • Teacher: • 郑扣根（Zheng Kougen） • Prof. Dr. Mr. … • zhengkg@263.net.cn • zkg@cs.zju.edu.cn • TA lxhzju@cs.zju.edu.cn “OS Homework”

2. Operating Systems (操作系统原理) • Refs: • Kernighan and Pike, The UNIX Programming Environment, Prentice-Hall, 1984. • W.R. Stevens, Advanced Programming in the UNIX Environment, Prentice-Hall, 1992 • W.R. Stevens, UNIX Network Programming I, Prentice-Hall, 1997. • W.R. Stevens, UNIX Network Programming II, Prentice-Hall, 1998. • www.kernel.org

3. CHAPTER 1: INTRODUCTION • What is an Operating System? • Mainframe Systems • Desktop Systems • Multiprocessor Systems • Distributed Systems • Clustered System • Real -Time Systems • Handheld Systems • Feature Migration • Computing Environments

4. WHAT IS AN OPERATING SYSTEM? An operating system (操作系统) • manages the computer resources, such as CPUs, Memories, Hard disks, and acts as an intermediary between the computer hardware and the computer user, • provides the system services to user programs, • provides an environment for executing programs.

5. What Is an Operating System? The components of a computer system

6. What Is an Operating System? The components of a computer system • Hardware – provides basic computing resources (CPU, memory, I/O devices). • Operating system – controls and coordinates the use of the hardware among the various application programs for the various users. • Applications programs – define the ways in which the system resources are used to solve the computing problems of the users (compilers, database systems, video games, business programs). • Users (people, machines, other computers).

7. What Is an Operating System? User view • PC users（PC用户）： The OS is designed to mostly for ease of use, with some attention paid to performance, and none paid to resource utilization. • Mainframe or minicomputer users (大型机和小型机用户)：The OS is designed to maximize resource utilization. • Workstation users（工作站用户）： The OS is designed to compromise between resource utilization and individual usability. • Handheld users （手持设备用户）： Mostly for individual usability, but performance per amount of batter life is important as well.

8. What Is an Operating System? System view • An operating system is a resource allocator （分配器） • An operating system is a control program that manages the execution of user programs to prevent errors and improper use of the computer. • An operating system is to execute user programs and to make solving user problems easier. • What is part of the OS • An OS is anything a vendor ships. • An OS is the kernel （内核）part and all else are applications. The matter of what constitutes an OS is becoming important (Microsoft case in 1998)

9. What Is an Operating System? System goals • OS goals • Convenience: Make the computer convenient to use. • Efficiency: Use the computer hardware in an efficient manner. • Building an OS is a complex task • Designing and implementation • Revising and updating • Hardware support. • To find out What the OS is and what it does, let us trace the evolution (not revolution) of OS.

10. MAINFRAME SYSTEMS (大型机系统) • No OS （无操作系统） • Batched OS（批处理操作系统） • Multiprogrammed OS （多道程序操作系统） • Time-sharing OS （多时操作系统）

11. Mainframe Systems: No OS • Designer, Implementer, Operator, User • Designer, Implementer / Operator, User • Drawbacks: • Scheduling time • Setup time • slow

12. Mainframe Systems: Batch OS • The OS • was always resident in memory • automatically transferred control from one job to another. • Batching: • Programmers submitted jobs in a job control languages (shell, awk, perl) • Operators batched together jobs with similar needs and ran them through the computer as a group. • Drawbacks: • fast CPU and slow I/O devices.

13. Mainframe Systems: Multiprogrammed OS • Multiprogrammed OS (vs. uniprogrammed OS) • Keeping many jobs in memory (see the next slide) • Switching to another job if the CPU is idle • As long as at least one job needs to execute, the CPU is never idle. • Multiprogrammed OS • Job scheduling for selecting a job to load into memory • CPU scheduling for selecting which job to run • Memory management • Protection. • Drawback: not interactive

14. Mainframe Systems: Multiprogrammed OS

15. Mainframe Systems: Time-sharing OS • Memory sharing multiprogramming • Memory sharing + time sharing  multiprogramming + interaction (or multi-tasking) • The CPU is rapidly multiplexed among several jobs that are kept in memory. (I/O operation is terribly slow!) • Time-sharing OS • Memory management (virtual memory) and protection • File system, disk management • Process synchronization (同步) and communication • Deadlock handling （死锁处理）.

16. DESKTOP SYSTEMS • Personal computers • computer system dedicated to a single user. • I/O devices – keyboards, mice, display screens, small printers. • Individuals have sole use of computer and do not need advanced CPU utilization of protection features. • User convenience and responsiveness not maximizing CPU and peripheral utilization • Can adopt some of the technology developed for larger operating system. • Not much of utilization • Protection, and so on • Many possible OSes: (Windows, MacOS, UNIX, Linux)

17. PARALLEL AND DISTRIBUTED SYSTEMS • Two types • Tightly coupled systems （紧耦合系统） • Parallel systems or multiprocessor systems • Processors share memory and a clock; communication usually takes place through the shared memory. • Loosed coupled systems（松耦合系统） • Distributed systems and clustered systems • Each processor has its own local memory; processors communicate with one another through various communications lines, such as high-speed buses or telephone lines.

18. Parallel and distributed systems: Parallel systems • Advantages of parallel systems: • Increased throughput • Economy of scale • Increased reliability • graceful degradation (The ability to continue providing service proportional to the level of surviving hardware). fail-soft systems (systems designed for graceful degration) • Asymmetric multiprocessing （非对称处理） • Master processor schedules and allocated work to slave processors. • Each processor is assigned a specific task; • More common in extremely large systems

19. Parallel and distributed systems: Parallel systems • Symmetric multiprocessing (SMP) （对称处理） • Each processor runs an identical copy of the operating system. • Many processes can run at once without performance deterioration. • Most modern operating systems support SMP • SMP and ASMP may be the result of either hardware and software

20. Parallel and distributed systems: Distributed systems • Advantages of distributed systems. • Resources Sharing • Computation speed up – load sharing • Reliability • Communications • Requires networking infrastructure. • Local area networks (LAN) or Wide area networks (WAN) • May be either client-server or peer-to-peer systems.

21. Parallel and distributed systems: Distributed systems

22. Parallel and distributed systems: Clustered systems（集群系统） • Clustering allows two or more systems to share storage. • Provides high reliability. • Asymmetric clustering: one server runs the application while other servers standby. • Symmetric clustering: all N hosts are running the application.

23. REAL-TIME SYSTEMS • Often used as a control device in a dedicated application such as controlling scientific experiments, medical imaging systems, industrial control systems, and some display systems. • Well-defined fixed-time constraints. • Real-Time systems may be either hard or soft real-time.

24. Real-Time Systems Hard real-time: • Secondary storage limited or absent, data stored in short term memory, or read-only memory (ROM) • Conflicts with time-sharing systems, not supported by general-purpose operating systems. • Soft real-time • Limited utility in industrial control of robotics • Useful in applications (multimedia, virtual reality) requiring advanced operating-system features.

25. HANDHELD SYSTEMS • Personal Digital Assistants (PDAs) (个人数字助理) • Cellular telephones（手机), Pocket PC, … • Issues: • Limited memory • Slow processors • Small display screens.

26. OS FEATURE MIGRATION

27. COMPUTING ENVIRONMENTS • Traditional computing • Web-Based Computing • Embedded Computing