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Operating System Overview
Chapter 2
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Operating System
•  A program that controls the execution of
application programs
•  An interface between applications and
hardware
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Operating System Objectives
•  Convenience
–  Makes the computer more convenient to use
•  Efficiency
–  Allows computer system resources to be
used in an efficient manner
•  Ability to evolve
–  Permit effective development, testing, and
introduction of new system functions
without interfering with service
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Layers of Computer System
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2
Services Provided by the
Operating System
•  Program development
–  Editors and debuggers
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Program execution
Access to I/O devices
Controlled access to files
Memory management
System access
Network support
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Services Provided by the
Operating System
•  Error detection and response
–  Internal and external hardware errors
•  Memory error
•  Device failure
–  Software errors
•  Arithmetic overflow
•  Access forbidden memory locations
–  Operating system cannot grant request of
application
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3
Services Provided by the
Operating System
•  Accounting
–  Collect usage statistics
–  Monitor performance
–  Used to anticipate future enhancements
–  Used for billing purposes
–  check out the log files of a unix system
•  where do you find this information?
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Operating System
•  Responsible for managing resources
•  An OS is just a program that is executed
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Computer System
I/O Devices
Memory
Operating
System
Software
I/O Controller
Printers,
keyboards,
digital camera,
etc.
I/O Controller
Programs
and Data
I/O Controller
Processor
Processor
Storage
OS
Programs
Data
Figure 2.2 The Operating System as Resource Manager
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Kernel
•  Portion of operating system that is in
main memory
•  Contains most frequently used functions
•  Also called the nucleus
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5
Linux
•  Brief discussion on linux
•  What is in the distributions:
–  http://lxr.linux.no/source/
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Why does an OS need to evolve?
•  Hardware upgrades plus new types of
hardware
•  New services
•  Fixes
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