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张惠娟 副教授Ms.zhj@163.com

实用操作系统概念

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内容框架 概述 体系结构 进程管理 内存管理 文件管理 外设管理

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ch1: Introduction

操作系统基本概念 操作系统发展 常用操作系统

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操作系统基本概念

计算机系统组成操作系统目标操作系统定义

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计算机系统组成 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.

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计算机系统组成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

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操作系统定义 Resource allocator

manages and allocates resources Control program

controls the execution of user programs and operations of I/O devices .

Kernel

the one program running at all times (all else being application programs).

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操作系统目标 A program that acts as an intermediary

between a user of a computer and the computer hardware.

Operating system goals:Make the computer system convenient to

use.Use the computer hardware in an efficient

manner.

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操作系统发展

发展阶段 发展规律

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发展阶段 Batch Systems（作业批处理） Time-Sharing Systems（分时系统） Personal-Computer Systems

（ PC系统） Parallel Systems （并行系统） Distributed Systems （分布系统） Real -Time Systems （实时系统）

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Batch Systems

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Resident monitor

( 驻留内存的监控程序 ) initial control in monitor

control transfers to job

when job completes control

transfers back to monitor

Batch Systems

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监控程序工作过程

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控制卡Special cards that tell the resident monitor which

programs to run $JOB

$FTN program to be compiled（源程序卡叠） $LOAD $RUN data for program（数据卡叠） $END

Batch Systems

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Problem Slow Performance ： I/O and CPU could not

overlap

SolutionMultiprogrammed Batch Systems speed up computation by loading jobs into memory from tapes and card reading and line printing done off-line.

Batch Systems

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Multiprogrammed Batch Systems Several jobs are kept in main memory at the same time, and the CPU is multiplexed among them.

Batch Systems

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对操作系统提出的新要求：I/O routine supplied by the system.Memory management – the system must

allocate the memory to several jobs.CPU scheduling – the system must choose

among several jobs ready to run.Allocation of devices.

Batch Systems

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Problem

提高了资源利用率，但缺少人机交互性。 Solution

Time-Sharing Systems

Batch Systems

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Time-Sharing Systems The CPU is multiplexed among several jobs that

are kept in memory and on disk (the CPU is allocated to a job only if the job is in memory).

A job is swapped in and out of memory to the disk.

On-line communication between the user and the system is provided;

On-line system must be available for users to access data and code.

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Personal-Computer Systems

Personal computers – computer system dedicated to a single user.

I/O devices – keyboards, mice, display screens, small printers.

User convenience and responsiveness.

Can adopt technology developed for larger operating system’ often individuals have sole use of computer and do not need advanced CPU utilization of protection features.

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Parallel Systems

Tightly coupled system – processors share memory and a clock; communication usually takes place through the shared memory.

Advantages of parallel system: Increased throughputEconomical Increased reliability

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Parallel Systems

Symmetric multiprocessing (SMP)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

Asymmetric multiprocessingEach processor is assigned a specific task; master

processor schedules and allocates work to slave processors.

More common in extremely large systems

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Symmetric multiprocessing

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Distributed Systems Distribute the computation among several

physical processors. Loosely coupled system – each processor has its

own local memory; processors communicate with one another through various communications lines, such as high-speed buses or telephone lines.

Advantages of distributed systems.Resources Sharing Computation speed up – load sharing ReliabilityCommunications

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Distributed Systems

Network Operating Systemprovides file sharing provides communication schemeruns independently from other computers on

the networkDistributed Operating System

less autonomy between computersgives the impression there is a single

operating system controlling the network.

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Real-Time Systems Well-defined fixed-time constraints. Hard real-time system.

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 systemLimited utility in industrial control or roboticsUseful in applications (multimedia, virtual reality)

requiring advanced operating-system features.

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发展规律 操作系统发展是由低层硬件、软件技 术与上层应用需求的发展所推动的 操作系统每一步发展都是权衡的结果

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常用操作系统 微软 OS产品 UNIX产品 自由软件 IBM 的 OS产品 其它 OS产品

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微软 OS产品

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UNIX产品发展

产生： 69 年 AT＆ T 公司贝尔实验室 第二阶段（ 73-79 ）：免费扩散第三阶段（ 75-85 ）：商用版本的出现（ 77年） 和三大主线的形成第四阶段（ 80年代后期）两大阵营和标准化第五阶段（ 90年代至今）共同面对外来竞争、

两大阵营淡化

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早期优点：– 内核结构小巧精湛– 接口简洁统一– 功能丰富实用– 用高级语言编写和好的结构导致可移植性好– 源码免费开放

早期缺点：– 缺乏图形界面– 内核单体结构可扩充性差

UNIX产品

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现在这些优缺点有的还在，有的没有了– 结构越来越庞大– 源码免费开放和简单许可证形式促进了早期的普及，但也导致各变种间的不兼容

– 图形界面大大增强– 内核仍是单体结构– 源码不开放后又开始开放

UNIX产品

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自由软件软件按提供方式和是否盈利划分为三种模式 :

商业软件、共享软件、自由软件自由软件的自由（ free）有两个含义：

可免费提供任何用户使用 其源码公开和可自由修改

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自由软件Linux发展

1990－ 91 芬兰赫尔辛基大学计算机系大学生Linus Torvalds

91年底 Linus在赫尔辛基大学 FTP服务器发布93 年 Linux 1.0，完全自由版权98年开始 Linux热

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自由软件 linux特点

免费、源代码开放具有出色的稳定性和速度性能功能完善，尤其网络功能丰富硬件需求低用户程序众多（而且大部分是免费软件），硬件支持广泛，程序兼容性好

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自由软件 linux未来

Linux受欢迎的原因 客观原因： Linux本身成本、性能和可能性等优势

主观原因：反微软情绪另一种声音：审慎和怀疑 业余爱好者开发 自由软件的技术支持和服务支持 Linux结构和功能上的不足优点和优势仍占主导地位：服务器 OS市场第二

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IBM 的 OS产品 AIX 5L IBM RS/6000和 SP结点上的高端 UNIX zOS IBM z/900大型主机系统 64 位专有 OS VM和 VSE S38/s370/S360大型主机系统 OS/400 IBM AS/400服务器专有 OS（原小型机） OS/2 Warp 4.0： IBM PS/2微机 PC DOS 7和 PC DOS 2000： IBM PC个人机

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其它 os

Mac OS 10 美国 APPLE公司 Macintosh微机NetWare 5 美国 Novell公司的网络操作系统

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小节 理解操作系统定义 操作系统发展的原因和各个阶段特点

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Exercise

阅读 p3-p16

P17

1.1 、 1.6 、 1.9