操作系统名词解释整理.doc

=名词解释=Operating system: operating system is a program that manages the computer hardware. The operating system is the one program running at all times on the computer (usually called the kernel), with all else being systems programs and application programs.操作系统：操作系统一个管理计算机硬件的程序，他一直运行着，管理着各种系统资源Multiprogramming: Multiprogramming is one of the most important aspects of operating systems. Multiprogramming increases CPU utilization by organizing jobs (code and data) so that the CPU always has one to execute.多程序设计：是操作系统中最重要的部分之一，通过组织工作提高CPU利用率，保证了CPU始终在运行中。batch system: A batch system is one in which jobs are bundled together with the instructions necessary to allow them to be processed without intervention.批处理系统：将许多工作和指令捆绑在一起运行，使得它们不必等待插入，以此提高系统效率。time-sharing system: time sharing is a logical extension of by switching among them, but the switches occur so frequently that the users can interact with each program while it is running.分时系统：是对多道程序设计的逻辑扩展。通过在多个作业间转换CPU，可以同时执行多个作业，但是这种转换发生的如此频繁以至于用户在程序运行的同时可以与计算机交互。Real-time system: A real-time system has well-defined, fixed time constraints. Processing must be done within the defined constraints, or the system will fail.实时系统：实时系统具有明确定义的、不变的时间约束。处理过程必须在规定的时间内完成，否则系统就失效了。DMA: It is an essential feature of all modern computers, as it allows devices to transfer data without subjecting the CPU to a heavy overhead.直接内存访问：一种不经过CPU而直接从内存存取数据的数据交换模式。System call: System call provide the interface between a running program and the operating system.系统调用：系统调用为运行中的程序和操作系统提供了一个接口。Microkernel: the microkernel approach structures the operating system by removing all nonessential components from the kernel and implementing them as system and user-level programs.微内核：微内核将所有不必要的组件从内核中去掉，并将它们作为系统和用户层程序来实现。Process: It is program in execution。进程：一个正在运行的程序PCB: each process is represented in the operating system by a process control block (PCB). A PCB contains many pieces of information associated with a specific process.PCB:操作系统通过进程控制块（PCB）表示进程，一个PCB存储了进程的许多信息。Job scheduler: the long-term scheduler, the job scheduler, selects processes which are spooled to a mass-storage device and loads them into memory for execution.作业调度：又称长程调度，从存储器中选择进程并将其载入内存。CPU scheduler: the short-term scheduler, selects from among the processes that are ready to execute and allocates the CPU to one of them.CPU调度：又称近程调度，从这些进程中选择就绪进程并为之分配CPU。Thread: A thread is basic unit of CPU utilization; it comprises a thread ID, a program counter, a register set, and a stack.线程：线程是一个基本的CPU执行单元；它包含了一个线程ID，一个程序计数器，一个寄存器组合一个堆栈。Throughput: one measure of work is the number of processes that are completed per time unit.吞吐量：对工作量的一种测量单位，单位时间内运行完的进程数量。nonpreemptive/preemptive scheduling: Under nonpreemptive scheduling, once the CPU has been allocated to a process, the process keeps the CPU until it releases the CPU either by terminating or by switching to the wait state. A form of scheduling designed so that jobs can be interrupted and their resources transferred to more urgent jobs. An interrupted job can be either terminated completely or resumed tater.非抢占式/抢占式调度：在非抢占式调度下，一旦CPU分配给一个进程，那么该进程就会保持CPU直到终止或转换到等待状态。抢占式调度：允许进程被中断，使其资源用在更重要的地方。Dispatcher: the dispatcher is the module that gives the control of the CPU to the process selected by short-term scheduler.调度程序：调度程序是一个模块，他将CPU控制提交给短程调度程序选择的进程。Turnaround time: the interval from the time of submission of a process to the time of completion is the turnaround time.周转时间：从进程提交到进程完成的时间间隔。Waiting time: waiting time is the sum of the periods spent waiting in the ready queue.等待时间：进程在就绪队列中耗费时间的总和。Response time: response time is the time from the submission of a request until the first response is produced.响应时间：从进程提交到产生首次响应的时间。Critical section: critical section is a segment of code in which the process may be changing common variables, updating a table, writing a file, and so on.临界区：每个进程有一个代码段，被称之为临界区，进程在临界区内可能会修改公有变量、更新一个表、写一个文件等。Semaphore: A semaphore S is integer variable that, apart from initialization, is accessed only through two standard atomic operations: wait() and signal().信号量：信号量s是一个整形数，除初始化之外，对它的访问只能通过两个标准原子操作：wait和signal。Atomic operation: Atomic operation means an operation that completes in its entirety without interruption.原子操作：原子操作指不会被中断，一次运行完的操作。Deadlock: a set of blocked processes each holding a resource and waiting to acquire a resource held by another process in the set.死锁：一些进程各自拥有一个资源，同时等待着另一个已被占有的资源，造成互相锁定的情况。Starvation: starvation is a situation in which processes wait indefinitely within the semaphore.饥饿：饥饿是指一个进程在信号量中无休止的等待。Deadlock prevention: Restrain the ways request can be made, attacking four conditions.死锁预防：只要确保造成死锁的四个条件中任意一个不成立，就可以预防死锁。Deadlock avoidance: A decision is made dynamically whether the current resource allocation request will, if granted, potentially lead to a deadlock. Requires that the system has some additional a priori information available.死锁避免：就是要求操作系统预先提供进程在其生命周期里要请求和释放资源的信息。Logical address: An address generated by the CPU is commonly referred to as a logical address.逻辑地址：CPU产生的地址通常称之为逻辑地址Physical address: an address seen by the memory unit that is, the one loaded into the memory-address register of the memory is commonly referred to as a physical address.物理地址：物理地址是内存单元的地址，也就是被装入内存的内存地址寄存器的地址。Dynamic linking: linking is postponed until execution time.动态链接：动态链接直到进行时才进行链接。Contiguous allocation: In contiguous memory allocation, each process is contained in a single contiguous section of memory.连续分配：又称连续内存分配，每个进程都包含在一个单独的连续内存区中。External fragmentation: External fragmentation exists when there is enough total memory space to satisfy a request, but the available spaces are not contiguous; storage is fragmented into a large number of small holes.外部碎片：伴随着进程的装入和移除，空闲内存空间被分成了众多的小块。当这些存在的内存空间的总大小可以满足一个请求时，外部碎片存在，但它却是不连续的（这样就不能满足请求）；存储器被分成了众多的碎片（小的分区）Internal fragmentation: memory that is internal to a partition but is not being used.内部碎片：内存在一个块内部，但不被使用。Page: logical memory broken into fixed-sized blocks of the same size as frames called pages页：把逻辑内存分成同样大小的块，称为页。Frame: physical memory broken into fixed-sized blocks called frames帧：把物理内存分为固定大小的块，称为帧。Segmentation: segmentation is a memory-management scheme that supports this user view of memory . A logical address space is a collection of segments. Each segment has a name and a length.分段：分段是一种内存管理机制，他支持内存的用户视角。逻辑地址是段的集合。每个段都有其名称和长度。Thrashing: This high paging activity is called thrashing. A process is thrashing if it is spending more time paging than executing.抖动：也叫颠簸，高频率的换页行为，如果一个进程在换页上用的时间要多于运行时间，那么这个进程就在抖动。Working set: The set of pages in the most recent page references is the working set.工作集合：最近X个被引用的页集合。File: the operating system abstracts from the physical properties of its storage devices to define a logical storage unit, the file. A file is an abstract data type.文件：文件是记录在外存上相关信息的具体名称的集合。从用户角度而言，文件是逻辑外存的最小分配单元。FCB: A File Control Block (FCB) is a file system structure in which the state of an open file is maintained.FCB: 文件控制块FCB是系统为管理文件而设置的一个数据结构.FCB是文件存在的标志,它记录了系统管理文件所需要的全部信息.Logical file structure: 文件逻辑结构：文件逻辑结构是从用户观点出发所看到的文件组织形式，是用户可以直接处理的数据及其结构physical file structure: 文件物理结构：文件物理结构是指文件在外存上的存储组织形式，它直接关系到存储器空间的利用率。Sequential access: sequential access is the simplest access method which information in the file is processed in order, one record after the other.顺序访问：最为简单的访问方式，文件信息按顺序，一个接一个得处理Direct access: A file is made up of fixed-length logical records that allow programs to read and write records rapidly in no particular order.直接访问：文件由固定长度的逻辑记录组成，以允许程序按任意顺序进行读写。Directory: the directory records informationsuch as name, location, size, and typefor all files on that volume.目录：目录是文件说明的集合，用于文件的描述与控制，包含名字，位置，大小和类型等信息Contiguous allocation: contiguous allocation requires that each file occupy a set of contiguous blocks on the disk.连续分配：连续分配方法要求每个文件在磁盘上占有一组连续的块。Linked allocation: with linked allocation, each file is in a linked list of disk blocks; the disk blocks may be scattered anywhere on the disk. 链接分配：采用链接分配，每个文件都是磁盘块的链表，磁盘块分部在磁盘的任何地方。Indexed allocation: each file has its own index block, which is an array of disk-block addresses. the i-th entry in the index block points to the i-th block of the file.索引分配：每个文件都有其空间的索引块，这是一个磁盘块地址的数组。索引块的第i个条目指向文件的第i个块。Seek time: Seek time is the time for the disk to move the heads to the cylinder containing the desired sector.寻道时间：寻道时间是磁臂将磁头移动到包含目标扇区的柱面的时间。Rotational latency: Rotational latency is the additional time waiting for the disk to rotate the desired sector to the disk head.旋转延迟：是磁盘需要将目标扇区转动到磁头下的时间。=上课提问题目=Chapter 11. What is the three main purpose of OS? 操作系统的目的？Answer: resource allocation，control program and a interface。资源分配 程序控制和接口。2. What are the three major activities of an operating system in regard to secondary-storage management? Answer: Free-space management. 空间管理Storage allocation. 存储分配Disk scheduling.磁盘调度3. What is the purpose of the command interpreter（命令解释程序）? Why is it usually separate from the kernel? Answer: It reads commands from the user or from a file of commands and executes them, usually by turning them into one or more system calls. It is usually not part of the kernel since the command interpreter is subject to changes.它从用户或者命令文件中读取命令，并常常把他们转化为系统调用的形式。和核心分离的原因是命令解释器容易受各种变化的影响。4. What is the main advantage for an operating-system designer of using a virtual-machine architecture? What is the main advantage for a user?对操作系统设计者而言，虚拟机技术的好处是什么？对用户的好处是什么？Answer: The system is easy to debug, and security problems are easy to solve. Virtual machines also provide a good platform for operating system research since many different operating systems may run on one physical system.系统容易调试，安全问题也容易解决。此外，可以将多种操作系统运行在一个物理系统上，为研究操作系统提供了较好的平台。Chapter 2What are the main advantages of the microkernel approach to system design?微核模式的好处？Answer: Benefits typically include the following (a) adding a new service does not require modifying the kernel, (b) it is more secure as more operations are done in user mode than in kernel mode, and (c) a simpler kernel design and functionality typically results in a more reliable operating system.好处有：a.当增加新的服务、功能时不用改变核心。b.由于大部分的操作运行在用户模式下，因此变得更为安全。c.微核模式使得系统更为可靠。2. Why do some systems store the operating system in firmware, and others on disk?为什么有些系统把操作系统固化在固件上，而有些则写在磁盘中？Answer: For certain devices, such as handheld PDAs and cellular telephones, a disk with a file system may be not be available for the device. In this situation, the operating system must be stored in firmware.对一些掌上电脑或者手机而言，无法做到提供一个内置的磁盘和操作系统，因此只能存在固件内。3. How could a system be designed to allow a choice of operating systems to boot from? What would the bootstrap program need to do?如何设计系统实现选择引导的功能？引导程序需要做什么？Answer: Consider a system that would like to run both Windows XP and three different distributions of Linux (e.g., RedHat, Debian, and Mandrake). Each operating system will be stored on disk. During system boot-up, a special program (which we will call the boot manager) will determine which operating system to boot into. This means that rather initially booting to an operating system, the boot manager will first run during system startup. It is this boot manager that is responsible for determining which system to boot into. Typically boot managers must be stored at certain locations of the hard disk to be recognized during system startup. Boot managers often provide the user with a selection of systems to boot into; boot managers are also typically designed to boot into a default operating system if no choice is selected by the user考虑到我们可能同时安装XP和其他的一些LINUX系统。每个操作系统都存放在磁盘上。在系统启动时，一个特殊的程序（我们称之为引导管理程序）会决定启动哪个操作系统。这意味着，在操作系统运行前，引导程序应该随着系统启动而运行。一般而言，该程序存放在硬盘上一个确定的位置以便于系统启动时读取。引导程序还会为用户提供一个操作系统的界面，另外，需要设置一个默认启动的操作系统以防止用户未做任何选择。Chapter 31. Describe the differences among short-term, medium-term, and longterm scheduling. (课后题目)写出短调度，中调度和长调度的区别Answer:Short-term (CPU scheduler)selects from jobs in memory those jobs that are ready to execute and allocates the CPU to them.短程调度（CPU调度）从内存中选取就绪进程，并为之分配CPUMedium-termused especially with time-sharing systems as an intermediate scheduling level. A swapping scheme is implemented to remove partially run programs from memory and reinstate them later to continue where they left off.中程调度有些操作系统（如分时系统）可能会引入另外一种中间级的调度。它将进程从内存中移除，稍后再把进程重新载入内存并从停止的地方继续运行。Long-term (job scheduler)determines which jobs are brought into memory for processing. 长程调度（工作调度）选择进程并调入内存。The primary difference is in the frequency of their execution. The short-term must select a new process quite often. Long-term is used much less often since it handles placing jobs in the system and may wait a while for a job to finish before it admits another one. 他们主要的区别在于运行的频繁程度。短程调度程序必须要频繁的为CPU选择一个新进程。对长程调度来说，在它为系统选择进程，直到该进程结束并设置新进程的期间，它并不会频繁执行。 2. Describe the actions taken by a kernel to context-switch between processes. (课后题目)简述当进程间进行上下文切换时内核所采取的措施。Answer: In general, the operating system must save the state of the currently running process and restore the state of the process scheduled to be run next. Saving the state of a process typically includes the values of all the CPU registers in addition to memory allocation. Context switches must also perform many architecture-specific operations, including flushing data and instruction caches.3.When a process creates a new process using the fork() operation, which of the following state is shared between the parent process and the child process?当一个进程里有FORK指令创建一个子进程时，以下的哪些选项父进程和子进程时共享的？ a. Stack b. Heap c. Shared memory segmentAnswer: Only the shared memory segments are shared between the parent process and the newly forked child process. Copies of the stack and the heap are made for the newly created process.Chapter 61. Prove Petersons solution is rightTwo process solutionAssume that the LOAD and STORE instructions are atomic; that is, cannot be interrupted.The two processes share two variables:int turn; Boolean flag2The variable turn indicates whose turn it is to enter the critical section. Turn表示轮到谁进入临界区 The flag array is used to indicate if a process is ready to enter the critical section. flagi = true implies that process Pi is ready! Flagi表示进程i已经准备好Algorithm for Process Pi19do flagi = TRUE; / i准备完毕 turn = j;/轮到j运行 while ( flagj & turn = j); /等待j运行完毕 CRITICAL SECTION /临界区，i执行操作 flagi = FALSE;/i未准备好 REMAINDER SECTION while (TRUE)do flag j:= TRUE; turn = i; while (flag i and turn = i) ; critical section flag j = FALSE; remainder section while (TRUE)2. Prove Dekkers solution is rightvar boolean flag2 ; / flag0=flag1=FALSE; int turn; /turn=i/j;Pi:do flagi=TRUE;/ i准备完毕 while (flagj) / j准备完毕时 if (turn=j) / 如果j在运行中 flagi=FALSE; / i改为未准备好 while (turn=j) ; /等待j执行完 flagi=TRUE; /i改为准备好 Critical Section I /执行i的临界操作 turn=j;/ 接下来轮到j执行 flagi=FALSE;/ i改为未准备好 Remainder Section while(1)Pj:do flagj=TRUE; while (flagi) if (turn=i) flagj=FALSE; while (turn=i) ; flagj=TRUE; Critical Section j turn=i; flagj=FALSE; Remainder Section while(1);3. Show that, if the wait() and signal() semaphore operations are not executed atomically, then mutual exclusion may be violated. Semaphore operations now defined aswait(S) :S.value-;if (S.value 0) add this process to S.L;block;signal(S) : S.value+;if (S.value = 0) remove a process P from S.L;wakeup(P);4. If we interchange the order of two wait() semaphore operations in Consumer Process or Producer Process, what will happen?The structure of Producer Processdo produce an item in nextp wait(empty);wait(mutex); add nextp to buffer signal(mutex);signal(full); while (1);structure of the Consumer Processdo wait(full);wait(mutex); remove an item from buffer to nextc signal(mutex);signal(empty); consume the item in nextc while (1);分析：在生产者消费者问题中，如果将两个 wait 操作，即 wait(full)和 wait(mutex)互换位置，或者 wait(empty)和 wait(mutex)互换位置，都可能引起死锁。考虑系统中缓冲区全满时，若一生产者进程先执行了 wait(mutex)操作并获得成功，当再执行 wait(empty)操作时，它将因失败而进入阻塞状态，它期待消费者执行 signal(empty)来唤醒自己，在此之前，它不可能执行 signal(mutex)操作，从而使企图通过 wait(mutex)进入自己的临界区的其他生产者和所有的消费者进程全部进入阻塞状态，从而引起系统死锁。类似地，消费者进程若先执行 wait(mutex)，后执行 wait(full)，同样可能造成死锁。 signal(full)和 signal(mutex)互换位置，或者 signal(empty)和 signal(mutex)互换位置，则不会引起死锁，其影响只是使临界资源的释放略为推迟一些。Chapter 81. Consider a logical address space of eight pages of 1024 words each,mapped onto a physical memory of 32 frames.a. How many bits are there in the logical address?b. How many bits are there in the physical address?2. Why are segmentation and paging sometimes combined into one scheme?(课后习题)Answer: Segmentation and paging are often combined in order to improve upon each other. Segmented paging is helpful when the page table becomes very large. A large contiguous section of the page table that is unused can be collapsed into a single segment table entry with a page-table address of zero. Paged se