overview of operating systems
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Chapters 1 and 2. Overview of Operating Systems. Introduction. Twin aims of an operating system are: User convenience System performance Performance measures depend on the computing environment Number of requests serviced per unit time, etc. Introduction. Fundamental tasks of an OS - PowerPoint PPT PresentationTRANSCRIPT
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
Slide No: 1Copyright ©2005
Overview of Operating Systems
Chapters 1 and 2
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
Slide No: 2Copyright ©2005
Introduction
• Twin aims of an operating system are:– User convenience– System performance
* Performance measures depend on the computing environment
* Number of requests serviced per unit time, etc
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
Slide No: 3Copyright ©2005
Introduction
• Fundamental tasks of an OS
- Management of Programs
* Organize their execution by sharing the CPU
* Ensure good user service and efficient use
- Management of Resources
* Efficient allocation/de-allocation without
constraining user programs
- Security and Protection
* Ensure absence of interference with programs and
resources by entities within and outside the OS
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
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Overview of security and protection threats
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
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OS and the Computer System
• In this module, we study
- Fundamental features of computer systems that are
important to an OS
* Memory hierarchy
* Interrupt structure
* I/O organization
- Fundamentals of how a program interacts with an OS
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
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Memory utilization during operation of an OS
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
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Model of a Computer System
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
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Fields of Program Status Word (PSW)
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
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(a) Program (b) State of CPU after executing COMPARE instruction
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
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Memory hierarchy containing cache, main memory and disk
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
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Memory hierarchy
• Cache memory * Organization – Cache block or cache line -- Inclusive or exclusive -- Direct, fully associative, set associative * Different levels of caches – Why? How many levels? * Cache hit ratio – What factors influence it?
• Main memory * Memory protection * Virtual memory?
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
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Memory protection using bound registers
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
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A schematic of virtual memory operation
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
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Input/Output organization
• Involvement of the CPU in I/O operations
-- Should be the minimum possible due to imbalance
between CPU and I/O speeds
-- CPU should be free to execute instructions while
I/O operations are in progress
• Different I/O modes
-- Programmed I/O
-- Interrupt I/O
-- Direct memory access (DMA)
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
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Input Output Modes
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
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Interrupts
• An interrupt signals the occurrence of an event to the CPU
• The CPU is diverted to execution of an OS routine
• Different classes of interrupts convey occurrence of different kinds of events
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
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Classes of Interrupts
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
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The interrupt action
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
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Steps in interrupt action
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
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An operating system in its computing environment
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
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Interrupt driven operation of a kernel
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
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System Call
• A system call is a request made by a program through a
special instruction called a `software interrupt’ instruction
• The software interrupt is a program interrupt
• When a software interrupt occurs, the interrupt hardware transfers control to a routine of the OS
• The operand of the software interrupt instruction indicates what kind of request is being made by a program
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
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System Calls
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
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Interrupt processing and scheduling
Chapter 1: Introduction Dhamdhere: Operating Systems—A Concept-Based Approach
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Simple and nested interrupt processing