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CSS430 Introduction Textbook Ch1 – Ch2. These slides were compiled from the OSC textbook slides (Silberschatz, Galvin, and Gagne) and the instructor’s class materials. Course Objectives. You will: Study the fundamental concepts of operating systems Practice the logical design using Java - PowerPoint PPT Presentation
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CSS430 Introduction 1
CSS430 IntroductionCSS430 IntroductionTextbook Ch1 – Ch2Textbook Ch1 – Ch2
These slides were compiled from the OSC textbook slides (Silberschatz, Galvin, and Gagne) and the instructor’s class materials.
CSS430 Introduction 2
Course Objectives You will:
Study the fundamental concepts of operating systems
Practice the logical design using Java But not:
Learn how to use/hack Windows and Linux If this is your main objective, you should take
R140/145/R708 of UW Computing Training http://www.washington.edu/computing/training
Skill up system programming with C++ Program 1 will deal with several system calls, but if this is
your main interest, you should take CSS432, CSS434 or other C++ programming courses.
Other Noteworthy OSes Distributed OSes All blends of *NIX Any windows competitor
IBM PS/2 NeXT OS Commodore 64 Embedded OSes Low-power OSes
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Important Time Lines Program 1: System calls and shell Program 2: Scheduler Midterm: Process Management Program 3: Synchronization Program 4: Paging Final: Memory/File Management Project: Unix-like file system(Check the syllabus for their due dates.)
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Important Web Pages and Email Addresses
Our class web:http://courses.washington.edu/css430/index.html
Java:http://java.sun.com/j2se/1.4/docs/api/index.html
Instructor’s email:{mfukuda, ksung, or rynn}@u.washington.edu
Class discussion mailing list:Use the message board.
Assignment submission:Use Catalyst drop box.
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What is an Operating System Goals
Making the computer system convenient to use Using computer hardware in an efficient
manner Definitions
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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Computer System Components
OS - Intermediary The OS acts on our behalf as a micro-
manager An OS acts as an intermediary
between the computer and the user It should use resources fairly and
efficiently; ease of use It should protect users from one
another, and from the kernelCSS430 Introduction 8
From the Text “an OS is similar to a government”
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More from the Dino Book “Like a government, the OS
performs no useful function by itself”
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O.S. & Computer Architecture As hardware is introduced, Oses are
built to make the hardware useable As Oses evolve, it becomes obvious
that certain hardware elements could simplify the operation of the kernel
So, a back-and-forth cycle exists.
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Operating Systems History Batch systems: Multiprogramming: IBM360 Time-sharing systems: Multics, Unix Personal-computer systems: Windows,
Linux Distributed systems: Amoeba, Mach
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Batch Systems A job is assembled of the program,
the data, and some control information (in control cards).
Programmers pass their jobs to an operator.
The operator batched together jobs.
OS transfers control from one job to another.
Each job output is sent back to the programmer.
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Multiprogramming Several jobs are kept in main
memory at the same time. OS picks one of them to execute. The job may have to wait for a slow
I/O operation to complete. OS switches to and executes
another job. To facilitate multiprogramming, OS
needs: Job scheduling Memory management
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Time-Sharing Systems This is a logical extension of
multiprogramming. Each user has at least one
separate program in memory. A program in execution is referred
to as a process. Process switch occur so
frequently that the users can interact with each program while it is running.
File system allows users to access data and program interactively.
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Personal-Computer Systems
Personal computers – computer system dedicated to a single user.
User convenience and responsiveness Can adopt technology developed for larger
operating systems’ some features. At its beginning, a single user system didn’t not
need advanced CPU utilization and protection. Later, file protection is necessary to avoid virus. Overall, the same OS concepts are appropriate
for the various different classes of computers.
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Parallel Systems Multiprocessor systems with more than one CPU
in close communication (in one box). Tightly coupled system – processors share
memory and a clock; shared-memory-based communication.
Advantages of parallel system: Increased throughput Economical Increased reliability
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Distributed Systems Loosely coupled system – each processor has its
own local memory; message-based communication through various communications lines, such as SAN, LAN, WAN or telephone lines.
Advantages of distributed systems. Resources Sharing (Printer, DB, special devices) Performance (load sharing, process migration) Reliability Communications
http://directory.google.com/Top/Computers/Software/Operating_Systems/Network/Distributed/
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Real-Time Systems Dedicated to a single application: controlling
scientific experiments, medical imaging systems, industrial, and military control systems (ex. Dam control, nuclear reactor, missile guiding, etc.).
Hard deadline Hard real-time system.
Data stored in short-term memory or ROM Conflicts with time-sharing systems
Soft real-time system Best effort to meet the deadline Useful in applications (multimedia, virtual
reality, QoS)
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Computer Hardware
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Synchronous I/O During execution, each
program needs I/O operations to receive keyboard inputs, open files, and print out results.
At the early computer era, a program had to wait for an I/O operation to be completed. (Synchronous I/O)
This frequently causes CPU idle.
requesting processwaiting
device driver
Interrupt handler
Hardwaredata transfer
user
kernel
time
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Async I/O and Interrupts Asynchronous I/O
returns control to a user program without waiting for the I/O to complete.
When the I/O is completed, an interrupt occurs to CPU that temporarily suspends the user program and handles the I/O device.
requesting processcontinuing
device driver
Interrupt handler
Hardwaredata transfer
user
kernel
time
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Discussions 11. What tasks should OS perform in
order to suspend and resume a program? List them.
Program suspension
Program resumption
1.2...
1.2...
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Hardware Protection Purpose:
With resource sharing, many programs could be affected by a bug in one program.
Incorrect or malicious resource accesses cause a hardware trap to the operating system.
Dual-Mode Operation: User mode: no privileged instructions allowed. Kernel mode: Privileged instructions allowed.
I/O Protection: all privileged Memory Protection: A region from the base to the limit
register allowed to use CPU Protection: CPU allowed to use until the timer
gets 0.
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Dual-Mode Operations Provide hardware support to differentiate
between at least two modes of operations.1. User mode – execution done on behalf of a
user.2. Monitor mode (also supervisor mode,
system mode, or Kernel mode) – execution done on behalf of operating system.
Switching between two modes Device interrupts, hardware traps, system calls
cause a trap to the kernel mode The operating system returns to the user mode
after servicing requests.
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System Calls
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Discussions 2 Early computers did not have interrupts, timers,
and/or privileged instructions. What features was OS unable to facilitate?
Features not supported by HW
Features not facilitated by OS
Asynchronous I/O and interruptsTimers
Privileged instructions
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Discussions 3 List three distinct events upon which OS
can get back CPU from the current user program.
1.
2.
3.
Project 1 – System Calls & Shells
This warmup exercise has two parts: A C/C++ app that makes direct
system calls to UNIX A Shell.java program that runs with
ThreadOS
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Part 1 Experiment with User-to-OS APIs System calls in C/C++ on Unix
See the list of system calls you are to use in the assignment
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Part 2 To get started, download the
ThreadOS files at /usr/apps/css430/ThreadOS/
Grab the class files, too! You’ll need these more than the src for
hw1
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Grading Guide See
http://courses.washington.edu/css430/prog/prog1.html
More on this Thursday
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