lecture 01 introduction
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Lecture 01 Introduction. What is an Operating System? The Evolution of Operating Systems Course Outline. What is an Operating System?. A program that acts as an intermediary between a user of a computer and the computer hardware. Operating system goals: Execute user programs - PowerPoint PPT PresentationTRANSCRIPT
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Fall 2000 M.B. Ibáñez
Lecture 01Introduction
What is an Operating System?The Evolution of Operating Systems
Course Outline
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What is an Operating System?
• A program that acts as an intermediary between a user of a computer and the computer hardware.
• Operating system goals:– Execute user programs – Make solving user problems easier– Allocate resources in a efficient and fair way
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Abstract View of System Components
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Hardware
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lots of different components,with different speds,different protocols for communication
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user 1 user 2 user n
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They want low cost and efficient services
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compiler text editor database system
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They want to have an easy life (don’t have to worry about speeds,use of file instead of blocks, large memory, etc)
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Operating System
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Services given by an Operating System
• Efficient program execution– Keeping all the devices busy– Good throughput for the user
• Access to I/O devices• Controlled access to system and files• Error detection and response• Accounting
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Evolution of Operating SystemsSerial Processing
• From the late 1940s to the mid-1950s• There was no Operating System
– These machines were run from a console, consisting of display lights, toggle switches, some form of input device, and a printer
• Job scheduling– A user used a sign-up sheet to reserve machine time.
• How to run a job?– Load the compiler and source program into memory– Save the object program– Loading and linking together the object program and common functions
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Evolution of Operating SystemsSimple Batch Systems
• Mid-1950s• The users did not interact directly with the computer system.
The operator would sort programs into batches with similar requirements.
• The user prepared a job. A Monitor executed the job.$JOB$FTN <FORTRAN instructions>$LOAD$RUN <data>$END
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Memory Layout For a Resident Monitor
Boundary
InterruptProcessing
DeviceDrivers
JobSequencing
Control LanguageInterpreter
UserProgram
Area
Monitor
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From Operating Systems.Internals and Design Principles.W. Stalling. Prentice Hall
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There are some hardware features desirable
• Memory protection the user program should not alter the monitor’s
area• Timer
to prevent a single job from monopolizing the system
• Privileged instructions I/O instructions by example
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Multiprogrammed Batch Systems
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time
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time
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Effects of Multiprogramming
Uniprogramming Multiprogramming
Processor use 17% 33%
Memory use 30% 67%
Disk use 33% 67%
Printer use 33% 67%
Elapsed time 30 min. 15 min.
Throughput rate 6 jobs/hr 12 jobs/hr
Mean response time 18 min. 10 min.
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From Operating Systems.Internals and Design Principles.W. Stalling. Prentice Hall
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Time-sharing systems
• 1960s, they become common early 1970s• Multiprogramming allows the processor to handle multiple
batch jobs at a time– Main objective: Maximize processor use
• Multiprogramming can be used to handle multiple interactive jobs: time -sharing– Main objective: Minimize response time
• Processor time is shared among multiple users• Multiple users simultaneously access the system through
terminals
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Primitive Time-sharing Operating System
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Monitorjob 1free
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Monitorfreejob 2
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Monitorfreejob2job3
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Monitorfreejob1job3
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New problems for the Operating Systems
• Multiple jobs are in memory– They must be protected from interfering with each other
• Multiple interactive users– The file system must be protected so that only authorized
users have access to a particular file
• The contention for resources, such as printers and mass storage devices, must be handled
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Characteristics of Modern Operating Systems.What forces a change?
Developments in hardware
• Multiprocessor machines• Greatly increased machine
speed• High-speed network
attachments• Increasing size and variety
of memory storage services
New applications
• Multimedia applications• Internet and Web access• client/server computing
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Characteristics of Modern Operating Systems Microkernel architecture
• A microkerner architecture assigns only a few essential functions to the kernel, such as– Address spaces– Interprocess communication– Basic scheduling
• The microkernel approach simplifies implementation, provides flexibility, and is well suited to a distributed environment
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Characteristics of Modern Operating SystemsMultithreading
• Multithreading– technique in which a process, executing an application,
is divided into threads that can run simultaneously
• Thread– dispatchable unit of work– executes sequentially and is interruptable
• Process – collection of one or more threads
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Characteristics of Modern Operating Systems Symmetric multiprocessing (SMP)
• Systems with multiple multiprocessors– there are multiple processors– these processors share same main memory and I/O facilities– All processors can perform the same functions
• Advantages over uniprocessor architectures– Performance– Availability– Incremental growth– Scaling
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Characteristics of Modern Operating Systems Distributed operating systems
• provides the illusion of a single main memory
• used for distributed file system
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Outline of the Course
• Processes• Memory• I/O devices• File systems• Protection and security