Operating systems ICOM 5007

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Operating systems ICOM 5007

• Webpage - http//ece.uprm.edu/noack/icom5007
• Includes
• Project
• Labs
• Standard methodology lectures and exams

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Purpose and Objectives

• Purpose
• To introduce the principal concepts of operating
  systems and to give experience in programming
  concurrent processes as used in developing
  operating systems
• Objectives
• After completing this course you should be able
  to
• Understand the basic concepts of operating
  systems and concurrent interacting processes
• Be able to use these concepts either in
  programming operating systems or in designing and
  implementing other systems using concurrency

3
The ABET outcomes for ICOM 5007

• Understand the five resource types of an
  operating system
• Analyze the differences between Linux and Windows
  operating system structure
• Analyze the organization of Linux source code and
  describe how it accomodates various platforms and
  I/O devices
• Program and analyze performance of representative
  concurrency examples
• Relate memory management techniques to process
  structure and reliable OS functioning
• Analyze a typical device driver, understanding
  methods to link it to the OS as a whole
• Program a threaded application in a language
  supporting monitors such as Java
• Relate system security aspects to OS internals
• Analyze malware and hacking attacks as they
  relate to OS
• Define, implement and test a significant OS
  project
• Coordinate group accomplishment of the project
• Prepare and give oral and written project reports

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Operating Systems - Administrivia

• Prontuario - Please time-share and ask questions
• Info is in my homepage http//ece.uprm.edu/noack
• Make bookmark for ICOM5007
• Page contains
• prontuario
• Links to old exams and labs
• Links to authors webpage and resources
• Links to current assignments, writeups, and
  slides as developed
• Course includes
• Exams and lecture material
• Lab work
• Project (described in course page)
• Lab
• Partly in OS/Networking lab
• Individual programs, often using Linux source or
  Java threads

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More Administrivia

• Office hours
• Tuesday, Thursday 900 am 1030 am, 1230 pm
  200 pmAlso I am often available in the
  universal hour Tuesday and Thursday 1030 am
  1230 pm
• For in-office consultation I suggest calling on
  X3652 or emailing and will normally see you any
  time I am in the office). 
• I will answer questions after class or between
  classes in the classroom, but not when it
  interferes with the next class given by another
  professor.
• Email is often the best way to resolve detailed
  or short questions. I am easily available by
  email, even at odd times such as evenings and
  weekends.

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More Administrivia

• Save a tree.
• Except for exams, the prontuario is the last
  piece of paper to be passed out in class.
• All other material will be distributed through my
  web page http//ece.uprm.edu/noack. You are
  responsible for checking this page at least once
  per week, and when changes are announced in class
• Similarly, homework and projects are to be handed
  in as email enclosures and not hardcopy.
• Exams
• The exams will be held from 730-930 PM,
  February 17, March 17, and April 28, in S-227 or
  S-228, or S-229.
• If you have a conflict with a regular class or
  with an exam announced before this document is
  distributed please contact me. If an exam is
  announced for another class after this date, the
  other instructor is responsible for resolving the
  conflict.
• One compensatory free period will be given for
  each night exam.

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Operating Systems - More Trivia

• Lab instructor to be announced
• Projects
• Info on course page
• Try to form groups soon - three or four people
• Project can be
• Device driver or module
• Operating system utility
• Operating system modification/improvement
• More information on course page

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More Administrivia

• New textbook edition appeared in December 2007
• Do not buy the second edition (dark blue book)
• The older edition was six years old good but
  outdated
• Link to the text page coming soon to your
  neighborhood
• Email addresses and project names
• Please send an email with your name
• When you form a project group please give it an
  easily recognizable name put that name as part
  of any file you email. Also, send an email with
  the project name and copy it to all the group
  members
• In any document you turn in please put all your
  names and email addresses that allows me to put
  comments in the document and return them in
  email.
• Be kind to trees use email, not paper.

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Operating Systems - Basics

• An OS is a program that controls and shares the
• resources of a computing system, which are
• CPU time (or allotment in distributed systems)
• Memory allocation and swapping to background
• I/O device handling - the dirty details
• File systems
• Network devices, layers and protocols
• An OS is (after initial setup) an
  interrupt-driven program
• Interrupts may come from
• I/O devices
• Timer interrupts - time slicing and hangup
  recovery
• Software interrupts - system call mechanism

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Operating Systems - Structures

• Monolithic
• One big complicated layer between users and
  hardware
• Unix is a typical monolithic system
• Layered - with microkernel
• Example - Mach contains
• Processes
• Threads
• Messages
• Memory blocks
• and everything else is implemented in higher
  layers using these highly protected basics
• Virtual Machine
• VM360 (IBM) is an example
• The virtual machine layer is
• between hardware and client machines
• emulates a separate machine for each user session

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The basic layered structureof all operating
systems
Application layer
System call interface
Operating system
Hardware/software interface
Hardware components
The concentric shell picture
Layers as usually drawn
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More OS Structures

• The main OS program is often called the kernel
• The Kernel
• operates in privileged mode
• contains the device drivers and modules
• contains process, memory and file management
• is protected by the system call interface - the
  INT instruction in 80x86 architecture
• The system call interface
• Is implemented by the INT (in i386) or similar
  instruction
• Is used when a user program makes a system call
• Is the transition from user to kernel mode
• Keeps users from running kernel code

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Monolithic operating system structuree. g.
Unix/Linux
Application layer
System call interface
Process handling
File system routines
Memory management
Intermediate routine
Device driver
Device driver
Hardware
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Microkernel-based systeme. g. Mach (used for
distributed systems)
Application layer
Outer kernel I Could be Posix Compliant layer
Outer kernel II Could be VMS emulator
Outer kernel III Experimental OS?
Microkernel layer
Hardware entities (can be several)
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Virtual machine systemVM first secure OS for
IBM 360/370
Virtual machine layer
Hardware
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Inside Windows 2K
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Inside the Linux kernel
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The shell is not the kernel

• The shell is an ordinary user program
• It operates by creating processes that in turn do
  system calls or run programs
• It is the equivalent of COMMAND.COM in MS/DOS
• Shell programming is possible and is often done
  in OS utilities
• Extensions of shell programming include
• PERL
• awk and sed
• ksh, csh, bash and other enhanced shells

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The standard lies of OS

• There is a separate processor for each process
• The CPU is time-shared
• You really have all that memory
• Memory is loaded only when needed - demand paging
• You are really doing all those disk operations
• The operations are done when and if the OS
  pleases - the disk block cache idea
• That remote file system is really there
• Remote file system utilities are a little
  unpredictable
• The OS is really secure
• Ask the big kids

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Concurrency

• The theoretical core of OS
• An OS creates a set of processes that run
  concurrently
• A process is like a person - it has
• a stream of consciousness
• possessions - memory, files, data
• is created, reproduces, dies
• interacts with other processes
• In actuality, it is a program in execution
• Concurrent process misbehaviors
• Race conditions - unpredictable results because
  processes simultaneously modify data or devices
• Deadlocks - Each has what the other wants, nobody
  gets anywhere
• Starvation - some processes go hungry - others
  eat well

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Some operating system ideas

• Everything is a file - even devices
• This allows a program to work with human input,
  or a device, or a temporary or permanent file or
  even a network connection
• The file system provides access control for
  devices also protects raw disk operations from
  users
• Interrupt-driven behavior
• Example - windows - process is simultaneously
  sensitive to events from mouse, keyboard, process
  subsystem, and window manager
• Caching - Foreground and background copies
• Used in
• Cache memory
• Swapping
• The disk block cache - recent transactions are in
  memory
• Networking utilities
• Advantage operations take place at memory speeds

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What is changing in OS

• Applications
• More varieties of systems now need OS
• Embedded systems
• Mobile computing (cellphones, PDAs
• Desktop systems
• Servers and small enterprise systems
• Large distributed systems
• Hardware
• Multicore processors
• Gadgets
• Mobile computing (usually wireless)
• Server complexes
• Large distributed and redundant systems