Download Real-Time Operating Systems Hard and Soft Real

Real-Time Operating Systems
• In real-time applications, users need computer to
perform some actions in a timely
p
y manner
– To control activities in an external system, or to
participate in them
• If application takes too long to respond to an activity, a
failure can occur in the external system
– Response requirement indicates the largest value of
response time for which the system can function perfectly
– Deadline: time by which action should be performed
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Hard and Soft Real-Time Systems
• A hard real-time system meets response requirements
under all conditions
– It is typically dedicated to processing real-time
applications
– E.g., guidance and control applications
• A soft real-time system makes best effort to meet
response requirement of a real-time application
– Cannot
C
t guarantee
t that
th t it will
ill be
b able
bl tto meett it
• Meets requirements in a probabilistic manner
– E.g., reservation and banking applications
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Features of a Real-Time Operating
System
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Modern Operating Systems
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Summary
• A computing environment consists of a computer
system its interfaces with other systems
system,
systems, and the
services provided by its OS to users and programs
– Evolved with advances in computer technology
• Each computing environment was serviced by a
separate class of operating systems
– Batch processing systems
• Automate
A t
t transition
t
iti between
b t
jobs
j b
– Multiprogramming operating system
• Priority-based preemptive scheduling
– Time-sharing operating systems
• Round-robin scheduling with time-slicing
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Summary (continued)
– Real-time operating systems
• Priority-based
Priority based scheduling and deadline-aware
deadline aware scheduling
– Distributed operating system
• Lets programs share resources across network
– Modern operating system
• Modern computing environment has elements of all the
classic computing environments
• Uses most
ost co
concepts
cepts and
a d techniques
tec ques in classic
c ass c ope
operating
at g
systems
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