• Users (people, machines, other computers)用户 （人、机、其他计算机）.
Resources in computer system
指构成计算机系统所 必须的那些“硬”设 备
硬件资源
计
算
机
系
统
资
源
软件资源
程序和数据的集合
主机
中央处理机CPU 内存
存储设备（硬盘、软盘、光盘、磁带） 外部设备 I/O设备（键盘、显示器、打字机、鼠标）
Common Functions of Interrupts
• Interrupt transfers control to the interrupt service routine generally, through the interrupt vector, which contains the addresses of all the service routines
– User mode and kernel mode – Mode bit provided by hardware
• Provides ability to distinguish when system is running user code or kernel code
• Some instructions designated as privileged, only executable in kernel mode
Computer-System Operation
• I/O devices and the CPU can execute concurrently • Each device controller is in charge of a particular device
type • Each device controller has a local buffer • CPU moves data from/to main memory to/from local
1 Introduction 操作系统引论
• What is an operating system? • Development and Types of OS • The features of OS • The functions of OS
Computer System Organization
Abstract View of System structure
Computer system structure
• Hardware – provides basic computing resources (CPU, memory, I/O devices).提供基本的运算资源
• Operating system – controls and coordinates the use of the hardware among the various application programs for the various users.在各 种应用程序和用户之间控制与协调对硬件的使用
reboot – Typically stored in ROM or EPROM, generally
known as firmware – Initializes all aspects of system – Loads operating system kernel and starts
• System call changes mode to kernel, return from call resets it to user
Transition from User to Kernel Mode
Computer Startup
• bootstrap program is loaded at power-up or
• Interrupt architecture must save the address of the interrupted instruction
• A trap is a software-generated interrupt caused either
by an error or a user request • An operating system is interrupt driven
其它设备（MODEM、通信口）
系统软件（OS、Compiler、DBMS）
应用软件 （CAD、MIS、用户自己开发的系统等）
工具软件（软、硬件检测诊断程序）
User mode and kernel mode
• Dual-mode operation allows OS to protect itself and other system components
• 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
பைடு நூலகம்
Computer system structure(cont.)
• 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).应用程序-定义解决用户问题的资源使用 方式（编译、数据库、视频游戏、事务程序等）
buffers • I/O is from the device to local buffer of controller • Device controller informs CPU that it has finished its
operation by causing an interrupt