Role of the OS

  (Historically).
    Automated the loading of programs and data.

    Provided debugging/monitoring of running program.

  (Modern)
  Give a common and consistent interface to applications.
    Provides a standardized set of routines for accessing hardware.

    If specifics of hardware change,
      Functions of the OS reprogrammed rather than each application.

    Plug & play - autoconfigure new hardware.

  Make the system more manageble to user.
    Provides a standardized set of routines for performing tasks. 

    Allows users to click on icon of program to start.

    Drag & drop - move files

    Plug & play - autoconfigure new hardware.
    

Four general functions.
  Interface (see above)

  Most modern systems support multitasking if not parallel processing.

    Process manager - switching between tasks.

    Resource management - sharing of common resources, drives, printer,
      display, input devices, etc.

    Protection - with multiple tasks, OS guards each task from being stepped
      on by other tasks.

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