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CONTENTS
• Operating System
• Functions and Components of OS
• Types of OS
• Process and a program
• Real time operating system (RTOS)
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What is an Operating System
• An Operating System is a
collection of software that
manages computer hardware
resources and provides
common services for
computer programs.
• The OS is a vital component
of the system software in a
computer system. Application
programs usually require an
operating system to function
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Functions of OS
• Managing resources
• Providing a user interface
• Running applications
• Support for built in utility
programs
• Control to the computer hardware
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Components of OS
• Process management
• Memory management
• I/O Device management
• File system
• Protection
• Network management
• Network services
• User interface
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Types of OS
• Real time OS
• Single user, Single task
• Single user, Multi-tasking
• Multi user, Multi-tasking
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Features of OS
• Reliable
• Operational at all times
• Should coordinate and have good control of input and output
operations and the devices on which they are performed
• Enhance time sharing
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Examples of computing devices which use OS
• Computers
• Mobile phones
• 3D televisions
• Video game
• ATM
• Ticket Wending Machine
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Examples of computing devices which don’t use OS
• Speed meters
• Digital Watches
• Micro ovens
• Washing machines
• Calculators
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Advantages of OS
• Easy to use
• User friendly
• Intermadiate between all hardware’s and software’s of the
system
• No need to know any technical languages
• It’s the platform of all programs.
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Disadvantages of OS
• If any problems affected in OS, you may lose all the
contents which have been stored already.
• Unwanted user can use your own system
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Process and Program
• A process invoke or initiates a program. It is an instance of
a program that can be multiple and running the same
application.
• Example: Notepad is one program and can be opened
twice.
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Batch OS
• If the job is fully completed, then only another job will be
scheduled
• Increased CPU idleness
• The throughput of the system will decrease
– The number of jobs completed per unit time is called
throughput of the system
• Example: IBM, OS/2
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Multiprogramming OS
• Increased CPU utilization
• Increased throughput
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Multitasking OS
• Multitasking is an extension to multiprogramming OS
• The job will be executed in the time sharing mode
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MultiProcessor OS
• Increase throughput
• Reliability -> Fault Tolerance Systems
• Economical
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Real time OS
• An operating system intended to serve real-time application
requests
• The system which are strict deadly time bound are called
real time systems
• An RTOS has an advanced algorithm for scheduling.
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Algorithms used in RTOS
• Cooperative scheduling
• Preemptive scheduling
• Earliest Deadline First approach
• Stochastic digraphs with multi-threaded graph traversal.
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Scheduling in RTOS
• Running (executing on the CPU)
• Ready (ready to be executed)
• Blocked (waiting for an event, I/O for example).
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