operating system concepts 1.1 silberschatz, galvin...
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Silberschatz, Galvin and Gagne ©20021.1Operating System Concepts
Chapter 1: Introduction
What is an Operating System?Mainframe SystemsDesktop SystemsMultiprocessor SystemsDistributed Systems Clustered SystemReal -Time SystemsHandheld SystemsComputing Environments
Silberschatz, Galvin and Gagne ©20021.2Operating System Concepts
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 programsmake solving user problems easiermake the computer system convenient to use
Use the computer hardware in an efficient manner
Silberschatz, Galvin and Gagne ©20021.3Operating System Concepts
Computer System Components
1. Hardwareprovides basic computing resources (CPU, memory, I/O devices)
2. Operating systemcontrols and coordinates the use of the hardware among the various application programs for the various users
3. Applications programsdefine the ways in which the system resources are used to solve the computing problems of the users (compilers, database systems, video games, business programs)
4. Users(people, machines, other computers)
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Silberschatz, Galvin and Gagne ©20021.4Operating System Concepts
Abstract View of System Components
•Terminal•PC•Workstation
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System View
Resource allocatormanages and allocates resources.
Control programcontrols the execution of user programs and operations of I/O devices
Kernelthe one program running at all timesall else being application programs
Silberschatz, Galvin and Gagne ©20021.6Operating System Concepts
Mainframe Systems
Reduce setup time by batching similar jobs
Automatic job sequencingautomatically transfers control from one job to anotherfirst rudimentary operating system
Resident monitorinitial control in monitor control transfers to job when job completes control transfers back to monitor
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Silberschatz, Galvin and Gagne ©20021.7Operating System Concepts
Devices
Card reader20 cards/second !
Printer
DiskSignificant increase in speed and convenience
Job scheduling
Silberschatz, Galvin and Gagne ©20021.8Operating System Concepts
Memory Layout for a Simple Batch System
Silberschatz, Galvin and Gagne ©20021.9Operating System Concepts
Multi-programmed Batch Systems
• Several jobs are kept in main memory at the same time• CPU is multiplexed among them
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Silberschatz, Galvin and Gagne ©20021.10Operating System Concepts
OS Features Needed for Multiprogramming
I/O routine supplied by the system
Memory managementsystem must allocate the memory to several jobs
CPU schedulingsystem must choose among several jobs ready to run
Allocation of devices
Silberschatz, Galvin and Gagne ©20021.11Operating System Concepts
Time-Sharing Systems–Interactive Computing
CPU is multiplexed several jobs that are kept in memory and on diskCPU is allocated to a job only if the job is in memory
A job swapped in and out of memory to the diskVirtual memory systemJob becomes process
Direct user interactionoperating system runs job for useronce finished, it seeks next job from user
Users to access data and codeFile system
Silberschatz, Galvin and Gagne ©20021.12Operating System Concepts
Desktop Systems
Personal computerscomputer system dedicated to a single user
I/O deviceskeyboards, mice, display screens, small printers.
User convenience and responsivenessadopt technology developed for larger system
individuals have sole use of computer and may not need advanced CPU utilization or protection features
operating system varies DOS, OS/2, Windows, MacOS, UNIX, Linux
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Silberschatz, Galvin and Gagne ©20021.13Operating System Concepts
Parallel Systems
Multiprocessor systemsmore than one CPU in close communication
Tightly coupled systemprocessors share memory and a clockcommunication through the shared memory
Advantages of parallel system: Increased throughputEconomicalIncreased reliability
graceful degradationfail-soft systems
Silberschatz, Galvin and Gagne ©20021.14Operating System Concepts
Parallel Systems (Cont.)
Symmetric multiprocessing (SMP)Each processor runs and identical copy of the operating systemMany processes can run at once without performance deterioration.Most modern operating systems support SMP
Asymmetric multiprocessingEach processor is assigned a specific taskMaster processor allocates work to slave processorsMore common in extremely large systems
Silberschatz, Galvin and Gagne ©20021.15Operating System Concepts
Symmetric Multiprocessing Architecture
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Distributed Systems
Distribute the computation among several processors
Loosely coupled systemeach processor has its own local memoryprocessors communicate via high-speed buses or low-speed telephone lines.
Advantages of distributed systemsResources Sharing Computation speed up – load sharing ReliabilityCommunications
Silberschatz, Galvin and Gagne ©20021.17Operating System Concepts
Distributed Systems (cont)
Requires networking infrastructure:Local area networks (LAN)Wide area networks (WAN)
client-serverComputer serverFile server
peer-to-peerEx: world-wide web
Silberschatz, Galvin and Gagne ©20021.18Operating System Concepts
General Structure of Client-Server
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Silberschatz, Galvin and Gagne ©20021.19Operating System Concepts
Distributed Systems
Operating system supportNetwork protocols
IP, TCP, UDPApplication protocols
ftp, http, sip
OS vs. NOS
True Distributed OS:User presents jobs to Dist-OSHigh degree of transparency
Silberschatz, Galvin and Gagne ©20021.20Operating System Concepts
Clustered Systems
Clustering allows two or more systems to share storage
Higher degree of sharing of resourcesHigh-bandwidth connection
Provides high reliabilityAsymmetric clustering
one server runs the application while other servers standby
Symmetric clustering: all hosts are running the application
Silberschatz, Galvin and Gagne ©20021.21Operating System Concepts
Real-Time Systems
Often used as a control device in a dedicated applicationcontrolling scientific experimentsmedical imaging systemsindustrial control systemssome display systems
Well-defined fixed-time constraintshard real-time: all tasks done on timesoft real-time: critical tasks have priority
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Silberschatz, Galvin and Gagne ©20021.22Operating System Concepts
Real-Time Systems (Cont.)
Hard real-time:Secondary storage limited or absentdata stored in short term memoryor read-only memory (ROM)Conflicts with time-sharing systemsnot supported by general-purpose operating systems
Soft real-timeLimited utility in industrial control of roboticsUseful in applications (multimedia, virtual reality) requiring advanced operating-system features
Silberschatz, Galvin and Gagne ©20021.23Operating System Concepts
Handheld Systems
Personal Digital Assistants (PDAs)Cellular telephones
Issues:Limited memorySlow processorsSmall display screens
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Migration of Operating-System Concepts and Features