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Basics of Operating Systems : Distributed and Real systems

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Basics of Operating Systems : Distributed and Real systems

Recap

In the last class, you have learnt about

• Multiprogramming

• Time Sharing

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Objectives

On completion of this period, you would be able to know

• Distributed Systems

• Real Time Systems

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Distributed Systems

• Distributed systems are loosely coupled systems

• A Distributed computer system is a collection of

autonomous computer systems

• Distributed systems communicate with one another

through various communication lines like high speed buses

or telephone lines

• The processors in a distributed system may vary in size

and function

– Example: small microprocessors, workstations , minicomputer and

large general purpose computers

Distributed Systems (contd..)

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Distributed System

• Processors in distributed systems are referred by no. of

different names like, sites, nodes, computers, etc.

• Important reasons for building distributed systems are– Resource sharing

– Computation speedup

– Reliability

– Communication

• The key objective of a distributed operating system is

transparency

• Ideally, component and resource distribution should be

hidden from users and applications programs unless they

explicitly demand

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Distributed System

• A distributed operating system governs the operations of a

distributed computer systems and provides a virtual

machine abstraction to its users

• Distributed operating system usually provides the means

for system-wide sharing of resources, such as

computational capacity, files and I/O devices

• Distributed operating system facilitates access to remote

resources, communication with remote process and

distribution of computation

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Real-Time System

• Real-time systems has well defined, fixed time constraints

• Processing must be done with in the defined constraints, or

the system will fail

• For example:

• It would not do for a robot arm to be instructed to halt after it had

smashed into the car it was building

Real-Time System

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Real-Time System

• Real-time system is used as a control device in a dedicated

application

• Sensors bring data to computers

• Computer analyze data and adjust controls to modify the

sensor inputs

• Example:

• Scientific experiments, medical imaging systems, industrial

control systems etc..

• Real-time system functions correctly only if it returns the

correct result within its time constraints

Real-Time System

• A primary objective of real-time systems is to provide

quick event - response times, thus meet the scheduling

dead lines

• User convenience and resource utilization are of

secondary concern to real- time system designers

• Real-time operating systems usually rely on some

specific policies and techniques for doing their job

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Real-Time System

• Memory management in real-time systems is

comparatively less demanding then in other types of

multiprogramming systems

• The primary reason for this is that many process

permanently reside in memory in order to provide quick

response time

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Real-Time System

• File management is usually found only in larger installation

of real-time systems

• In fact, some embedded real-time systems, such as an

onboard automotive controller, may not even have any

secondary storage

• These include protection and access control

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Summary

• A primary objective of real-time systems is to provide

quick event - response times, and thus meet the

scheduling dead lines

• User convenience and resource utilization are of

secondary concern to real- time system designers

• A distributed computer system is a collection of

autonomous computer systems capable of

communication and cooperation via their hardware and

software interconnections

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Frequently Asked Questions

1. Explain about Real Time Operating System

2. Explain about Distributed Operating System

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Quiz

1. File management is usually found only in larger

installation of real-time systems

Yes

No

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Quiz

2. A distributed computer system is a collection of

autonomous computer systems capable of

communication and cooperation via their hardware and

software interconnections

Yes

No

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