Transcript Chap 1: Introduction

Operating Systems (操作系统原理)
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Text book:
 Dinosaur book （恐龙书）
 操作系统概念 (中译本)
Teacher:
 郑扣根（Zheng Kougen）
 Prof. Dr. Mr. …
 [email protected]
 [email protected]
TA
[email protected] “OS Homework”
Operating Systems (操作系统原理)
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Refs:
 Kernighan and Pike, The UNIX Programming
Environment, Prentice-Hall, 1984.
 W.R. Stevens, Advanced Programming in the UNIX
Environment, Prentice-Hall, 1992
 W.R. Stevens, UNIX Network Programming I,
Prentice-Hall, 1997.
 W.R. Stevens, UNIX Network Programming II,
Prentice-Hall, 1998.
 www.kernel.org
CHAPTER 1: INTRODUCTION
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What is an Operating System?
Mainframe Systems
Desktop Systems
Multiprocessor Systems
Distributed Systems
Clustered System
Real -Time Systems
Handheld Systems
Feature Migration
Computing Environments
WHAT IS AN OPERATING SYSTEM?
An operating system (操作系统)
 manages the computer resources, such as CPUs,
Memories, Hard disks, and acts as an
intermediary between the computer hardware
and the computer user,
 provides the system services to user programs,
 provides an environment for executing
programs.
What Is an Operating System?
The components of a computer system
What Is an Operating System?
The components of a computer system
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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.
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).
What Is an Operating System?
User view
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PC users（PC用户）： The OS is designed to mostly
for ease of use, with some attention paid to
performance, and none paid to resource utilization.
Mainframe or minicomputer users (大型机和小型机用
户)：The OS is designed to maximize resource
utilization.
Workstation users（工作站用户）： The OS is
designed to compromise between resource utilization
and individual usability.
Handheld users （手持设备用户）： Mostly for
individual usability, but performance per amount of
batter life is important as well.
What Is an Operating System?
System view
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An operating system is a resource allocator （分配器）
An operating system is a control program that manages
the execution of user programs to prevent errors and
improper use of the computer.
An operating system is to execute user programs and to
make solving user problems easier.
What is part of the OS
 An OS is anything a vendor ships.
 An OS is the kernel （内核）part and all else are
applications.
The matter of what constitutes an OS is becoming
important (Microsoft case in 1998)
What Is an Operating System?
System goals
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OS goals
 Convenience: Make the computer convenient to use.
 Efficiency: Use the computer hardware in an efficient
manner.
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Building an OS is a complex task
 Designing and implementation
 Revising and updating
 Hardware support.
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To find out What the OS is and what it does, let us trace the
evolution (not revolution) of OS.
MAINFRAME SYSTEMS (大型机系统)
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No OS （无操作系统）
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Batched OS（批处理操作系统）
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Multiprogrammed OS （多道程序操作系统）
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Time-sharing OS （多时操作系统）
Mainframe Systems: No OS
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Designer, Implementer, Operator, User
Designer, Implementer / Operator, User
Drawbacks:
 Scheduling time
 Setup time
 slow
Mainframe Systems: Batch OS
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The OS
 was always resident in memory
 automatically transferred control from one job to
another.
Batching:
 Programmers submitted jobs in a job control
languages (shell, awk, perl)
 Operators batched together jobs with similar needs
and ran them through the computer as a group.
Drawbacks:
 fast CPU and slow I/O devices.
Mainframe Systems: Multiprogrammed OS
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Multiprogrammed OS (vs. uniprogrammed OS)
 Keeping many jobs in memory (see the next slide)
 Switching to another job if the CPU is idle
 As long as at least one job needs to execute, the CPU is
never idle.
Multiprogrammed OS
 Job scheduling for selecting a job to load into memory
 CPU scheduling for selecting which job to run
 Memory management
 Protection.
Drawback: not interactive
Mainframe Systems: Multiprogrammed OS
Mainframe Systems: Time-sharing OS
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Memory sharing multiprogramming
Memory sharing + time sharing  multiprogramming +
interaction (or multi-tasking)
The CPU is rapidly multiplexed among several jobs that
are kept in memory. (I/O operation is terribly slow!)
Time-sharing OS
 Memory management (virtual memory) and protection
 File system, disk management
 Process synchronization (同步) and communication
 Deadlock handling （死锁处理）.
DESKTOP SYSTEMS
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Personal computers
 computer system dedicated to a single user.
 I/O devices – keyboards, mice, display screens, small
printers.
 Individuals have sole use of computer and do not need
advanced CPU utilization of protection features.
User convenience and responsiveness not maximizing
CPU and peripheral utilization
Can adopt some of the technology developed for larger
operating system.
 Not much of utilization
 Protection, and so on
Many possible OSes: (Windows, MacOS, UNIX, Linux)
PARALLEL AND DISTRIBUTED SYSTEMS
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Two types
 Tightly coupled systems （紧耦合系统）
 Parallel systems or multiprocessor systems
 Processors share memory and a clock;
communication usually takes place through the
shared memory.
 Loosed coupled systems（松耦合系统）
 Distributed systems and clustered systems
 Each processor has its own local memory;
processors communicate with one another
through various communications lines, such as
high-speed buses or telephone lines.
Parallel and distributed systems:
Parallel systems
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Advantages of parallel systems:
 Increased throughput
 Economy of scale
 Increased reliability
 graceful degradation (The ability to continue
providing service proportional to the level of
surviving hardware). fail-soft systems (systems
designed for graceful degration)
Asymmetric multiprocessing （非对称处理）
 Master processor schedules and allocated work to slave
processors.
 Each processor is assigned a specific task;
 More common in extremely large systems
Parallel and distributed systems:
Parallel systems
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Symmetric multiprocessing (SMP) （对称处理）
 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
SMP and ASMP may be the result of either hardware
and software
Parallel and distributed systems:
Distributed systems
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Advantages of distributed systems.
 Resources Sharing
 Computation speed up – load sharing
 Reliability
 Communications
Requires networking infrastructure.
Local area networks (LAN) or Wide area networks
(WAN)
May be either client-server or peer-to-peer systems.
Parallel and distributed systems:
Distributed systems
Parallel and distributed systems:
Clustered systems（集群系统）
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Clustering allows two or more systems to share storage.
Provides high reliability.
Asymmetric clustering: one server runs the application
while other servers standby.
Symmetric clustering: all N hosts are running the
application.
REAL-TIME SYSTEMS
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Often used as a control device in a dedicated
application such as controlling scientific experiments,
medical imaging systems, industrial control systems,
and some display systems.
Well-defined fixed-time constraints.
Real-Time systems may be either hard or soft real-time.
Real-Time Systems
Hard real-time:
 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.
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Soft real-time
 Limited utility in industrial control of robotics
 Useful in applications (multimedia, virtual reality)
requiring advanced operating-system features.
HANDHELD SYSTEMS
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Personal Digital Assistants (PDAs) (个人数字助理)
Cellular telephones（手机), Pocket PC, …
Issues:
 Limited memory
 Slow processors
 Small display screens.
OS FEATURE MIGRATION
COMPUTING ENVIRONMENTS
Traditional computing
 Web-Based Computing
 Embedded Computing
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