LINUX System : Lecture 2 OS and UNIX summary

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LINUX System Lecture 2OS and UNIX summary

• Bong-Soo Sohn
• Assistant Professor
• School of Computer Science and Engineering
• Chung-Ang University

Acknowledgement (i) wikipedia.org ,
(ii) http//www.doc.ic.ac.uk/wj
k/UnixIntro
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Operating Systems

• OS acts as an intermediary between user and HW
• Resource Manager
• Allocates and manages system resources (CPU,
  Memory, Disks, Networks, )
• Efficient and fair use of the resources
• Interface
• OS allows users and application programs to
  access system resources
• Controls the execution of user programs
  accurately
• Efficiently, Fairly, Safely(Accurately),
  Abstractly

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Computer System Structure

• HW provides basic computing resources
• CPU, memory, disk,
• OS Kernel
• direct control of underlying HW
• System call
• Programming interface to the services provided by
  the OS
• The one program running at all times on the
  computer is the kernel. Everything else is either
  a system program (shipped with OS) or an
  application program
• Application programs
• Define the ways in which the system resources are
  used to solve user problems
• executed thru shell/GUI.
• Ex) word processor, video games, etc

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Operating Systems

• Functionality
• Process Management
• CPU scheduling batch vs time-sharing
• Memory Management
• Memory allocation determine what is in memory
  when?
• Virtual memory a technique that gives an
  application program the impression that it has
  large contiguous working memory, while in fact it
  is physically fragmented and may even overflow on
  to disk storage.
• Disk and file system
• Device driver interface for communicating with
  HW devices
• Networking supports network protocols. (ex)
  TCP/IP
• Security authentication (login), authorization
  (file permission),
• UI GUI (Graphical User Interface), CLI (Command
  Line Interface)
• OS comes with application programs that provide
  an interface for managing OS.

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Storage Hierarchy

• Register, Cache, Main memory, Secondary Storage
  (disks), Magnetic tapes
• Why hierarchical structure?
• Speed
• Cost
• Volatility
• Caching
• Copying information into faster storage system.
• Faster storage checked first to determine if
  information is there
• Cachelt-gtmain memory, main memorylt-gtdisk
• Important principle, performed at many levels in
  computer

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OS Structures

• Multiprogramming
• a technique used to utilize maximum CPU time by
  running multiple programs simultanously
• Single user cannot keep CPU and I/O devices busy
  at all times.
• Multiprogramming organizes jobs (code and data)
  so CPU always has one to execute
• One job is selected and run via job scheduler
• When a running job has to wait for I/O, OS
  switches to another job
• Multitasking (time-sharing)
• CPU switches jobs so frequently that users can
  interact with each job while it is running.
• Creates interactive computing
• Response time can be controlled
• If processes dont fit in memory, swapping moves
  them in and out to run

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Operating Systems

• MS Windows
• Most popular on desktop computers
• Gaining popularity in servers.
• UNIX/LINUX
• Most popular in server environments
• LINUX are gaining popularity on desktop PC.

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UNIX System

• has been popular for more than two decades
• Portability
• Written mostly in C a few in assembly language
• Kernel size is small
• Multi-user, multi-tasking environment
• Stability
• Powerful networking capabilities
• Free, open source code(LINUX)

Suitable for using as a server
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UNIX History

• Created by Ken Thompson et al. ( a researcher at
  ATT Bell Lab)
• UNICS(1969) (shortened to UNIX later) first
  version
• Released Fifth version of UNIX
• kernel was rewritten in C, which was a big step
  forwards in terms of system portability (1973)
• LINUX
• Developed by Linus Torvalds, a finnish undergrad
  student, in 1991
• Free open source UNIX OS for PC
• Open source code nature means any one can add
  features and correct deficiencies.
• Turned in to collaboration of hundreds of
  volunteer developers around the world.
• Several different distributions (e.g. Redhat,
  Debian, etc)
• Distribution comprises a prepackaged kernel,
  system utilities, GUI, application programs

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LINUX

• Kernel
• Device driver support for various HW device
• Advanced processor and memory management
• Support different types of file system
• Shells / GUI two forms of command input
• Textual command line shells (e.g. C shell, )
• Graphical user interface (e.g. GNOME window
  manager)
• System utilities
• Virtually every UNIX system utilities were ported
  to LINUX
• Include daemons
• server program running as a background process
• Application programs
• Come with standard application programs
• e.g. vi, emacs, xv, gcc/g, xfig, latex,