上海交通大学：《操作系统 Operating System》课程教学资源（课件讲稿）OS-Introduction_Lec2

OPERATING SYSTEMS 1 龚玲 lgong@sjtu.edu.cn

OPERATING SYSTEMS 龚玲 lgong@sjtu.edu.cn 1

OPERATING SYSTEM Silberschatz,Galvin and Gagne c2007

Silberschatz, Galvin and Gagne ©2007 OPERATING SYSTEM

OBJECTIVES o To provide coverage of basic computer system organization o To provide a grand tour of the major operating systems components o http://developer.android.com/sdk/index.html

OBJECTIVES  To provide coverage of basic computer system organization  To provide a grand tour of the major operating systems components  http://developer.android.com/sdk/index.html

COMPUTER SYSTEM ORGANIZATION o Computer-system operation One or more CPUs,device controllers connect through common bus providing access to shared memory Concurrent execution of CPUs and devices competing for memory cycles mouse keyboard printer monitor disks on-line CPU disk controller USB controller graphics adapter memory

COMPUTER SYSTEM ORGANIZATION  Computer-system operation  One or more CPUs, device controllers connect through common bus providing access to shared memory  Concurrent execution of CPUs and devices competing for memory cycles 粗略的了解

OS TOOL:VIRTUAL MACHINE ABSTRACTION Application Virtual Machine Interface Operating System Physical Machine Interface Hardware o Software Engineering Problem: ·Turn hardware./software quirks→ what programmers want/need Optimize for convenience,utilization,security,reliability, etc... o For Any OS area (e.g.file systems,virtual memory, networking,scheduling): o What's the hardware interface?(physical reality) What's the application interface?(nicer abstraction)

OS TOOL: VIRTUAL MACHINE ABSTRACTION  Software Engineering Problem:  Turn hardware/software quirks  what programmers want/need  Optimize for convenience, utilization, security, reliability, etc…  For Any OS area (e.g. file systems, virtual memory, networking, scheduling):  What’s the hardware interface? (physical reality)  What’s the application interface? (nicer abstraction) Application Operating System Hardware Physical Machine Interface Virtual Machine Interface

COMPUTER SYSTEM STRUCTURE o Computer system can be divided into four components Hardware-provides basic computing resources oCPU,memory,I/O devices ·Operating system o Controls and coordinates use of hardware among various applications and users Application programs-define the ways in which the system resources are used to solve the computing problems of the users o Word processors,compilers,web browsers,database systems,video games 。Users o People,machines,other computers

COMPUTER SYSTEM STRUCTURE  Computer system can be divided into four components  Hardware – provides basic computing resources  CPU, memory, I/O devices  Operating system  Controls and coordinates use of hardware among various applications and users  Application programs – define the ways in which the system resources are used to solve the computing problems of the users  Word processors, compilers, web browsers, database systems, video games  Users  People, machines, other computers

FOUR COMPONENTS OF A COMPUTER SYSTEM user user user user 1 2 3 n compiler assembler text editor database system system and application programs operating system computer hardware

FOUR COMPONENTS OF A COMPUTER SYSTEM

OPERATING SYSTEM DEFINITION o Os is a resource allocator ·Manages all resources Decides between conflicting requests for efficient and fair resource use o OS is a control program Controls execution of programs to prevent errors and improper use of the computer

OPERATING SYSTEM DEFINITION  OS is a resource allocator  Manages all resources  Decides between conflicting requests for efficient and fair resource use  OS is a control program  Controls execution of programs to prevent errors and improper use of the computer

OPERATING SYSTEM DEFINITION (CONT.) o No universally accepted definition o"Everything a vendor ships when you order an operating system"is good approximation 。But varies wildly o "The one program running at all times on the computer"is the kernel.Everything else is either a system program (ships with the operating system)or an application program

OPERATING SYSTEM DEFINITION (CONT.)  No universally accepted definition  “Everything a vendor ships when you order an operating system” is good approximation  But varies wildly  “The one program running at all times on the computer” is the kernel. Everything else is either a system program (ships with the operating system) or an application program

WHAT DOES AN OPERATING SYSTEM DO? o Silerschatz and Gavin: “An OS is Similar to a government” 0 Coordinator and Traffic Cop: Manages all resources Settles conflicting requests for resources Prevent errors and improper use of the computer o Facilitator: Provides facilities that everyone needs Standard Libraries,Windowing systems Make application programming easier,faster,less error-prone o Some features reflect both tasks: E.g.File system is needed by everyone (Facilitator) But File system must be Protected(Traffic Cop)

WHAT DOES AN OPERATING SYSTEM DO?  Silerschatz and Gavin: “An OS is Similar to a government”  Coordinator and Traffic Cop:  Manages all resources  Settles conflicting requests for resources  Prevent errors and improper use of the computer  Facilitator:  Provides facilities that everyone needs  Standard Libraries, Windowing systems  Make application programming easier, faster, less error-prone  Some features reflect both tasks:  E.g. File system is needed by everyone (Facilitator)  But File system must be Protected (Traffic Cop)