Operating Systems (Third Edition): Chapter 1

OS3e_Chapter_01

Operating Systems (Third Edition)
Harvey M. Deitel, Paul J. Deitel, David R. Choffnes

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CHAPTER 1: Introduction to Operating Systems
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# Core Operating System Components
    * User interacts with the Operating System through
        - special application called shell
        - kernel: software that contains core components of OS

    * Components of a typical Operating System
        - process scheduler
        - memory manager
        - I/O manager
        - Interprocess Communication (IPC) manager
        - File System manager

# Operating System goals
    - Efficiency
    - Robustness
    - Scalability
    - Extensibility
    - Portability
    - Security
    - Protection
    - Interactivity
    - Usability

# Operating System Architectures
    * Monolithic Architecture
        - Every component contained in kernel
        - Every component can directly communicate with any other
        - Highly efficient because few calls cross from user space to kernel
          space.
        - Linux is broadly categorized as a monolithic OS
        - Difficult to trace bugs in the source
        - All codes execute with unrestricted access to the system, hence
          kernel is susceptible to damage from errant or malicious code.

    * Layered Architecture
        - Improves monolithic kernel design by grouping components
        - Components are grouped into layers on the basis of functions
          performed by them
        - Each layer communicates only with layers immediately above and below
          it.
        - Implementation of each layer can be modified without requiring any
          modification to other layers.
        - Requests by processes might have to pass through many layers before
          completion. Several calls may be required to communicate between
          layers.
        - System throughput is less than monolithic kernels.

    * Microkernel Architecture
        - Attempt to keep kernel small and scalable
        - High degree of modularity
        - Extensible, portable, and scalable
        - Increased level of inter-module communication
        - Microkernel does not rely on each component to execute. One or more
          components can fail without causing the OS to fail.
        - OS components like process management, networking, file system
          interaction, and device management execute outside the kernel with
          lower privilege level.

# Network and Distributed Operating Systems
    * Network Operating System
        - Client server network model.
        - Client computers request files, or processing time via appropriate
          networking protocol.
        - Allows processes to access resources on remote machines.

    * Distributed Operating Systems
        - Single operating system, but manages resources on more than one
          computer system.
        - Processes do not need to know the location of resources they use.
        - Need for complex algorithms to enable processes to communicate and
          share data among many computers.