Operating System Concepts–7th Edition,Jan 14,

1、Chapter 2: Operating-System StructuresFact or Fiction?Every non-trivial multiprogramming system is a timesharing system.Every non-trivial timesharing system is a multiprogramming system.Mnemonic DeviceMNMnMeNMn what? Just a mental trick for remembering things.Named after Mnemosyne, the personificati

2、on of memory and the mother of the nine Apollonian muses from Greek MythologySome Impeccable LogicEvery square is a rectangle, but not all rectangles are squares. Square Rectangle (alphabetically)Timesharing Multiprogramming (alphabetically)Every non-trivial timesharing system is a multiprogramming

3、system, but not every multiprogramming system is a timesharing system.Multiprogramming optimizes for throughputMaximizes useful work performed by CPU per unit timePure multiprogramming perhaps best for batch processingTimesharing optimizes for throughput subject to response timeResponse times must b

4、e small (less than 1 second) to create illusion that each user has a dedicated computer. Overhead of context-switching creates a drag on throughputBest for interactive computing environmentsChapter 2: Operating-System StructuresOperating System ServicesUser InterfaceSystem CallsTypes of System Calls

5、System ProgramsOperating System Design and ImplementationOperating System StructureVirtual MachinesOperating System GenerationSystem BootObjectivesTo describe the services an operating system provides to users, processes, and other systemsTo discuss the various ways of structuring an operating syste

6、mTo explain how operating systems are installed and customized and how they bootOS User ServicesOne set of operating-system services provides functions that are helpful to the user:User Interface - Almost all operating systems have a user interface (UI)Varies among Command-Line Interpreters (CLI), G

7、raphical User Interfaces (GUI), and Batch. Program Execution - The system must be able to load a program into memory and to run that program, end execution, either normally or abnormally (indicating error)I/O Operations - A running program may require I/O, which may involve a file or an I/O device.

8、File-System Operations - File system is of particular interest. Obviously, programs need to read and write files and directories, create and delete them, search them, list file Information, permission management.OS User ServicesCommunications Processes may exchange information, on the same computer

9、or between computers over a networkCommunications may be via shared memory or through message passing (packets moved by the OS)Error Detection OS needs to be constantly aware of possible errorsMay occur in the CPU, memory, I/O devices, or user programsFor each type of error, OS should take the appro

10、priate action to ensure correct and consistent computingDebugging facilities can greatly enhance the users and programmers abilities to use the system efficientlyOS System ServicesAnother set of OS functions exists to ensure efficient system operationResource Allocation - When multiple users or mult

11、iple jobs are running concurrently, resources must be allocated to each of themMany types of resources - Some (such as CPU cycles, main memory, and file storage) may have special allocation code (like scheduling or paging), others (such as I/O devices) may have general request and release code. Acco

12、unting - To keep track of which users use how much and what kinds of computer resources (e.g. print quota tracking)Protection and Security - The owners of information stored in a multi-user or networked computer system may want to control use of that information; concurrent processes should not inte

13、rfere with each otherProtection ensures controlled access to system resourcesSecurity from outsiders requires user authentication, extends to defending external I/O devices from invalid access attemptsOS User Interface Command LineCommand-Line Interface (CLI) allows direct command entryImplemented i

14、n the kernel or by a systems programSometimes multiple flavors implemented shellsKorn Shell (ksh), Bourne Shell, Bourne-Again Shell (bash)Primarily fetches and executes commands from userSometimes commands are built-in Shell footprint becomes proportional to functionalitySometimes commands are just

15、delegated (UNIX)Adding new features doesnt require shell modificationOS User Interface GUIUser-friendly desktop metaphor interfaceUsually mouse, keyboard, and monitorIcons represent files, programs, actions, etcVarious mouse buttons over objects in the interface cause various actions (provide inform

16、ation, options, execute function, open directory (known as a folder)First GUI was invented at Xerox PARC Alto (1973)Many systems now include both CLI and GUI interfacesMicrosoft Windows is GUI with CLI “command” shellApple Mac OS X has “Aqua” GUI interface with UNIX kernel underneath and shells avai

17、lableSolaris is CLI with optional GUI interfaces (Java Desktop, KDE)System CallsProgramming interface to the services provided by the OSMostly accessed by programs via a high-level Application Program Interface (API) rather than direct system call useOS frequently executes thousands of system calls

18、per secondThree most common APIsWin32 API for WindowsJava API for the Java Virtual Machine (JVM)POSIX API for POSIX-based systems (including virtually all versions of UNIX, Linux, and Mac OS X)Why use APIs rather than system calls?Portability, convenience, ease-of-use, encapsulationExample of System

19、 CallsSystem call sequence to copy the contents of one file to another fileSystem Call ImplementationTypically, a number associated with each system callSystem-call interface maintains a table indexed according to these numbersSystem call interface invokes the intended system call in OS kernel and r

20、eturns status of the system call and any return valuesThe caller need know nothing about how the system call is implementedJust needs to obey API and understand what OS will do as a result callMost details of OS interface hidden from programmer by API Managed by run-time support library (set of func

21、tions built into libraries included with compiler)API System Call OS RelationshipStandard C Library ExampleC program invoking printf() library call, which calls write() system callSystem Call Parameter PassingInformation is typically passed via parameters to the system callType and amount of informa

22、tion vary according to OS and callThree general methods used to pass parameters to the OSSimplest: pass the parameters in registers In some cases, may be more parameters than registersParameters stored in a table, or memory block, and address of block passed as a parameter in a register This approac

23、h taken by Linux and SolarisParameters placed, or pushed, onto the stack by the program and popped off the stack by the operating systemAdvantages: block and stack methods do not limit the number or length of parameters being passedParameter Passing via TableTypes of System CallsSee Section 2.4 of T

24、extbookProcess controlFile managementDevice managementInformation maintenanceCommunicationsMS-DOS Single Tasking System(a) At system startup, (b) Running a programFreeBSD Multi-tasking SystemSystem ProgramsSystem programs provide a convenient environment for program development and execution. The ca

25、n be divided into:File manipulation Status informationFile modificationProgramming language supportProgram loading and executionCommunicationsApplication programsMost user views of the operation system are defined by system programs, not the actual system callsSolaris 10 dtrace Following System Call

26、System ProgramsProvide a convenient environment for program development and executionSome of them are simply user interfaces to system calls; others are considerably more complexFile management - Create, delete, copy, rename, print, dump, list, and generally manipulate files and directoriesStatus in

27、formationSome ask the system for info - date, time, amount of available memory, disk space, number of usersOthers provide detailed performance, logging, and debugging informationTypically, these programs format and print the output to the terminal or other output devicesSome systems implement a regi

28、stry - used to store and retrieve configuration informationSystem Programs (contd)File modificationText editors to create and modify filesSpecial commands to search contents of files or perform transformations of the textProgramming-language support - Compilers, assemblers, debuggers and interpreter

29、s sometimes providedProgram loading and execution- Absolute loaders, relocatable loaders, linkage editors, and overlay-loaders, debugging systems for higher-level and machine languageCommunications - Provide the mechanism for creating virtual connections among processes, users, and computer systemsA

30、llow users to send messages to one anothers screens, browse web pages, send electronic-mail messages, log in remotely, transfer files from one machine to anotherNational “Talk Like a Pirate” DayLexicon to surviving the dayAhoy!“Hello”Aye!“Why yes, I agree most heartily with everything you just said”

31、Aye aye!“Ill get right on that sir, as soon as my break is over”Thar she blows!Pirate equivalent of “Whoop, there it is!”O(jiān)perating System Design and ImplementationOS Design and Implementation not “solvable” due to conflicting stakeholders, but some approaches have proven successfulInternal structure

32、 of different Operating Systems can vary widelyStart by defining goals and specifications Affected by choice of hardware, type of systemUser goals and System goalsUser Goals operating system should be convenient to use, easy to learn, reliable, safe, and fastSystem Goals operating system should be e

33、asy to design, implement, and maintain, as well as flexible, reliable, error-free, and efficientOperating System Design and Implementation (Cont.)Important principle to separate WHAT from HOWPolicy: What will be done? Mechanism: How to do it?The separation of policy from mechanism is a very importan

34、t principle, it allows maximum flexibility if policy decisions are to be changed laterExample: I need a searchable set (WHAT)Could be a hash table (HOW)Could be a binary search tree (HOW) Simple Structure MS-DOS Written to provide most functionality using least spaceNot divided into modulesKind of l

35、ike a big ball of mudAlthough MS-DOS has some structure, its interfaces and levels of functionality are not well separatedOriginally designed for the Intel 8088 architecture8088 had no dual-mode bit (kernel versus user modes)MS-DOS had no choice but to leave the base hardware accessible to applicati

36、on programsHuge implications for security and protectionMS-DOS Layer StructureLayered ApproachThe operating system is divided into a number of layers (levels), each built on top of lower layers. The bottom layer (layer 0), is the hardware; the highest (layer N) is the user interface.With modularity,

37、 layers are selected such that each uses functions (operations) and services of only lower-level layersMakes testing and validation somewhat easierLayered Operating SystemWhat is the purpose of testing?To verify correctness?Nope. Thats just Americana and apple pie.Answer: To witness the existence of

38、 defects.A successful test case is one that reveals a defectNote: Testing is different than DebuggingSuccessful testing reveals the existence of defectsDebugging identifies and corrects the cause of defectsUNIXUNIX limited by hardware functionality, the original UNIX operating system had limited str

39、ucturing. The UNIX OS consists of two separable partsSystems programsThe kernelConsists of everything below the system-call interface and above the physical hardwareProvides the file system, CPU scheduling, memory management, and other operating-system functions; a large number of functions for one

40、levelUNIX System StructureMicrokernel System Structure Moves as much from the kernel into “user” spaceCommunication takes place between user modules using message passingBenefits:Easier to extend a microkernelEasier to port the operating system to new architecturesMore reliable (less code is running

41、 in kernel mode)More secureDetriments:Performance overhead of user space to kernel space communicationMac OS X StructureModulesMost modern operating systems implement kernel modulesUses object-oriented approachEach core component is separateEach talks to the others over known interfacesEach is loada

42、ble as needed within the kernelOverall, similar to layers but with more flexibleSolaris Modular ApproachVirtual MachinesA virtual machine takes the layered approach to its logical conclusion. It treats hardware and the operating system kernel as though they were all hardwareA virtual machine can pro

43、vide an interface identical to the underlying bare hardwareThe operating system creates the illusion of multiple processes, each executing on its own processor with its own (virtual) memoryGreat for testing new code on different platformsVirtual Machines (Cont.)The resources of the physical computer

44、 are shared to create the virtual machinesCPU scheduling can create the appearance that users have their own processorSpooling and a file system can provide virtual card readers and virtual line printersA normal user time-sharing terminal serves as the virtual machine operators consoleVirtual Machin

45、es (Cont.) (a) Non-virtual machine (b) Virtual machineNon-virtual MachineVirtual MachineVirtual Machines (Cont.)The virtual-machine concept provides complete protection of system resources since each virtual machine is isolated from all other virtual machines. This isolation, however, permits no dir

46、ect sharing of resources.A virtual-machine system is a perfect vehicle for operating-systems research and development. System development is done on the virtual machine, instead of on a physical machine and so does not disrupt normal system operation.The virtual machine concept is difficult to imple

47、ment due to the effort required to provide an exact duplicate to the underlying machineVMware ArchitectureThe Java Virtual MachineOperating System GenerationOperating systems are designed to run on any of a class of machines; the system must be configured for each specific computer siteSYSGEN progra

48、m obtains information concerning the specific configuration of the hardware systemBooting starting a computer by loading the kernelBootstrap program code stored in ROM that is able to locate the kernel, load it into memory, and start its executionEnd of Chapter 2PPT（全名：PowerPoint）是美國(guó)微軟公司出品的辦公軟件系列重要組

49、件之一（另外還有Excel、Word等）；最常用的就是用來(lái)制作幻燈片。MicrosoftOfficePowerPoint是一種演示文稿圖形程序，該軟件是功能強(qiáng)大的演示文稿制作軟件；可協(xié)助用戶獨(dú)自或聯(lián)機(jī)創(chuàng)建永恒的視覺(jué)效果；它增強(qiáng)了多媒體支持功能，利用該軟件制作的文稿，可以通過(guò)不同的方式播放，也可將演示文稿打印成一頁(yè)一頁(yè)的幻燈片，使用幻燈片機(jī)或投影儀播放，可以將演示文稿保存到光盤中以進(jìn)行分發(fā)，并可在幻燈片放映過(guò)程中播放音頻流或視項(xiàng)目列表; 新增項(xiàng)目; 修改項(xiàng)目; 刪除項(xiàng)目; 項(xiàng)目授權(quán); 項(xiàng)目任務(wù)統(tǒng)計(jì); 項(xiàng)目資源管理; 項(xiàng)目進(jìn)度管理; 項(xiàng)目任務(wù)包管理; 項(xiàng)目文檔管理; 項(xiàng)目費(fèi)用管理; 項(xiàng)目歸檔; 項(xiàng)

50、目查詢; 當(dāng)前任務(wù); 項(xiàng)目統(tǒng)計(jì)分析。4. 庫(kù)存管理掌握庫(kù)存的動(dòng)態(tài)流動(dòng)狀況，減少庫(kù)存資金的占用，加強(qiáng)資金的合理使用。選擇“庫(kù)存管理”模塊后，在主菜單下將出現(xiàn)庫(kù)存資料維護(hù)、入庫(kù)、出庫(kù)、庫(kù)存查詢、倉(cāng)庫(kù)資料維護(hù)、業(yè)務(wù)類型維護(hù)、貨物單位資料維護(hù)幾個(gè)子菜單。左方出現(xiàn)“存貨管理”模塊的樹狀結(jié)構(gòu)的庫(kù)存分類信息。右邊會(huì)出現(xiàn)庫(kù)存列表，當(dāng)沒(méi)有選擇庫(kù)存分類的時(shí)候，庫(kù)存資料列表將顯示所有庫(kù)存項(xiàng)目，按錄入時(shí)間排序;在選擇某個(gè)分類的時(shí)候，將顯示該分類下的庫(kù)存列表，庫(kù)存列表會(huì)把當(dāng)前的庫(kù)存數(shù)量顯示出來(lái)，點(diǎn)擊某庫(kù)存的鏈接將顯示庫(kù)存項(xiàng)目的詳細(xì)信息。此模塊包含以下主要功能：新增分類; 修改分類; 刪除分類; 新增存貨項(xiàng)目; 修改存貨

51、資料; 刪除存貨資料; 庫(kù)存查詢; 入庫(kù)登記; 出庫(kù)登記; 查詢存貨收發(fā)記錄; 倉(cāng)庫(kù)資料維護(hù); 業(yè)務(wù)類型資料維護(hù); 貨物單位資料維護(hù)。=原文出自【比特網(wǎng)】，轉(zhuǎn)載請(qǐng)保留原文鏈接：頻流。對(duì)用戶界面進(jìn)行了改進(jìn)并增強(qiáng)了對(duì)智能標(biāo)記的支持，可以更加便捷地查看和創(chuàng)建高品質(zhì)的演示文稿一套完整的PPT文件一般包含：片頭動(dòng)畫、PPT封面、前言、目錄、過(guò)渡頁(yè)、圖表頁(yè)、圖片頁(yè)、文字頁(yè)、封底、片尾動(dòng)畫等；所采用的素材有：文字、圖片、圖表、動(dòng)畫、聲音、影片等；國(guó)際領(lǐng)先的PPT設(shè)計(jì)公司有：themegallery、poweredtemplates、presentationload等；近年來(lái)，中國(guó)的PPT應(yīng)用水平逐步提高，應(yīng)

52、用領(lǐng)域越來(lái)越廣；PPT正成為人們工作生活的重要組成部分，在工作匯報(bào)、企業(yè)宣傳、產(chǎn)品推介、婚禮慶典、項(xiàng)目競(jìng)標(biāo)、管理咨詢等領(lǐng)域。敘利亞內(nèi)戰(zhàn)局勢(shì)急劇升級(jí)，國(guó)營(yíng)電視臺(tái)證實(shí)，國(guó)防部長(zhǎng)拉杰哈今天在首都的一次自殺式襲擊中被炸死，是敘利亞國(guó)內(nèi)沖突爆發(fā)以來(lái)，政府軍損失的最高級(jí)軍方官員，另外，內(nèi)政部長(zhǎng)、情報(bào)首長(zhǎng)也被炸傷。襲擊者是總統(tǒng)巴沙爾的一名近身侍衛(wèi)。敘利亞自由軍和伊斯蘭旅兩個(gè)反政府組織都宣稱對(duì)襲擊負(fù)責(zé)，但否認(rèn)事件是國(guó)營(yíng)電視臺(tái)所說(shuō)的自殺式襲擊，而是將fgdfgdfgdfgdgdfgdfgdfgdfgfhthhhfhh dhfdhdsfhgfhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh

53、hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhtttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttthhhhhhhhhhhhhaaaaaaaaaaahhhhttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttthhhhhhhhhhhhhhhhhhhhhhhhhvvvvvvvvvvvvvvvvvvvvvv炸彈事先放在會(huì)議室內(nèi)。事發(fā)后，敘利亞政府已經(jīng)任命了原參謀長(zhǎng)弗雷伊為新任國(guó)防部長(zhǎng)。敘利亞國(guó)營(yíng)

54、電視臺(tái)新聞節(jié)目周三迅速公布了事件，稱大馬士革的國(guó)家安全部門遭到自殺襲擊，當(dāng)時(shí)內(nèi)閣官員和軍方高層正在開會(huì)，多名官員嚴(yán)重受傷，國(guó)防部長(zhǎng)喪生。被炸死的敘利亞國(guó)防部長(zhǎng)拉杰哈，本月九號(hào)才剛剛出席過(guò)，敘利亞防空部隊(duì)的實(shí)彈演習(xí)，敘利亞電視臺(tái)也在拉哈杰死后，馬上播出他視察演習(xí)的畫面。另外，總統(tǒng)巴沙爾的姐夫、副國(guó)防部長(zhǎng)舒卡特，也在襲擊中喪生。近幾日以來(lái)，大馬士革一直在爆發(fā)激烈戰(zhàn)斗，沖突已經(jīng)越來(lái)越接近總統(tǒng)巴沙爾的權(quán)力核心。有上載到網(wǎng)絡(luò)的視頻顯示，在大馬士革的蘇塞村不斷傳出重型炮火聲。又有段視頻顯示，遜尼派社區(qū)米丹發(fā)生戰(zhàn)斗后，四處斷壁殘?jiān)?。此外，大馬士革西部也據(jù)稱有軍營(yíng)遇襲起火。連串沖突迫使近日大批敘民眾，當(dāng)中包括兩名敘利亞將軍，逃亡到鄰國(guó)土耳其。另外，有上載到網(wǎng)絡(luò)的視頻顯示，敘利亞自由軍在北部阿扎茲訓(xùn)練。有自由軍成員說(shuō)，（自己）本來(lái)效忠巴沙爾部隊(duì)，在政府軍濫殺平民后變節(jié)50PPT（全名：PowerPoint）是美國(guó)微軟公司出品的辦公軟件系列重要組件之一（另外還有Excel、Word等）；最常用的就是用來(lái)制作幻燈片。MicrosoftOfficePowerPoint是一