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✇ Team 7 ✇, image, image, 🍥 - Coggle Diagram

- - - - • Each component hides how it performs its job and presents a standard interface that other components can use to request its services.
    - - User Applications (TOP LAYER)
      - I/O Management (LOWER LAYER)
      - Message Interpreter (LOWER LAYER)
    - - (LAYER 4) User applications (USER SPACE)
      - (LAYER 3) I/O Management (KERNEL SPACE)
      - (LAYER 2) Message Interpreter (KERNEL SPACE)
      - (LAYER 1) Memory Management (KERNEL SPACE)
      - (LAYER 0) Processor Allocation and process scheduling (KERNEL SPACE)
    - - ▪modularity,
        
        ▪simplicity,
        
        ▪flexibility,
        
        ▪scalability,
        
        ▪portability
      - weakness
        
        ▪More risk of
        
        breakdown
        
        ▪Issues related to
        
        higher/lower layers
        
        ▪Sluggish operation
        
        mode on application
        
        ▪Data overhead
  - - - •Aimed at migrating services of an OS from monolithic kernel intouser level process
      - •Divide OS into several processes, each implements a single set of servoces
      - •Example: I/O servers, memory server,process server
      - ▪Developed to take out of the kernel as much functionality as possible,in order to:
        
        1.limit the code executed in privileged mode and
        
        to allow easy modifications and extensions.
        
        3.Allows us to build a number of different OS using the same micro-kernel
    - - ▪Components above microkernel communicate directly with one another,although using message that pass through the mircokernel itself
        
        ▪Microkernel validate messages, passes them between the components and grants access to hardware.
        
        ▪Example: C-DAC microkernel, Mach, Windows NT, chorus
  - - - • 1 source code
        
        • 1 program generated
        
        • No structure.
    - - • Designed to handle multiple related tasks.
      - They're typically complex applications that encompass several tightly coupled function
    - - STRENGH:
        
        •Highly efficient & good performance
        
        •Shared kernel space *
        
        •The monolithic kernel is a static single binary file (means only one file to run)
      - WEAKNESS:
        
        •Inflexible
        
        •No hidden information
        
        •Chaotic
        
        •Difficult to understand*
        
        •To add any new service, the entire operating system needs to be modified by the user.
  - - - ▪Networked and distributed are being used in network operating system.
      - ▪A network operating system (NOS) is a specialized operating system for a network device such a router,switch or firewall
      - ▪It enables process to access resources (e.g file) that reside on the other independent computers on a network
      - ▪The client computers in such a network request resources-such as files and processor time and the server respond with the approate resource.
    - - Networked and distributed : example of network OS provider
        
        MICROTIK
        
        ZYXEL
        
        CISCO
        
        dd-wrt.com
- - - - 1.Has ONE main processor(CPU)
        -to execute general purpose instruction set or program
        -can only execute one process at one time
        -if there multiple instructions/processes need to be executed, they will be queued up and be executed in turns
      - 2.Has other special purpose processors
        -built in every systems
        -to perform specific instruction set
        -able to do their work autonomously, without the management of OS
        -these microprocessor does not make single processor a multiple processor
  - - - 1.Have TWO or MORE processors in 'close contact'
        -also referred as parallel system or tightly coupled system
        -shares computer bus and full access to a common RAM
        -sometimes shares clock, peripheral devices
        -able to simultaneously execute two or more different instruction sets/programs
        -shares task to improve performance and to solve in less time
      - 2.Advantages
        -more processor meaning more work can be done in less time
        -when working on 1 task, it can be done faster, less error due to cooperation of multiple processors
      - 3.Scale economy
        -costs less than equivalent multiple single processor system, bcs they can share peripheral, mass storage, and power supplies
        -cheaper to store data on one disk when several programs operate on same data set
      - 4.More reliable
        -failure of one processor will not halt the system and operations, only slows down
        -when one processor fails, other remaining processors able to takeover the failed processor's task
        -slowing rate of any failed processor will be determined by the number of failed processors and total processors in the system
  - - - 1.Have connected MULTIPLE CPU's
        -the system uses multiple CPU's to complete a specific task
        -consists two or more individual computer systems that are merged
        -they share same storage space and the systems work together
        -they are closely linked via a LAN network or interconnect
      - 2.High availability
        -service or operation will continue even if on or more systems in the cluster fail
        -one layer of cluster software runs on cluster nodes
        -each nodes running its own instance of an operating system
        -each nodes able to monitor one or more of the others through the LAN network or interconnect
        -when monitored machine fails, the monitoring machine can take ownership of its storage and restart the applications that were running on the failed machine
        -users or clients of the applications can only see a brief interruption of a service
      - 3.Clustering structures
        -two structures; Asymmetrically and Symmetrically
        -Asymmetrically is the structure/system where only one machine that is operating while others in standby
        -when the working machine fails, another machine will takeover the task
        -Symmetrically is the structure/system where all machines will operate at the same time, while monitoring each other
        -when one or more monitored machine fails, the remaining monitoring machines will takeover the task
- - - - 1.Proprietary
        
        Programmers paid by company.
        
        Source codes are company secret.
        
        Registered as Intellectual Property.
      - 2.Only the final product is made available.
      - 3.Distributed directly to end user or via vendor.
      - 4.Have copyright/patented legally protected as intellectual property.
    - - For computers
      - For mobile phone
    - - 1.Full access to the service.
      - 2.Large-scale product for research and
        development.
      - 3.More usability.
      - 4.More security.
      - 5.More technical support.
    - - 1.User have no idea how it was made.
      - 2.Quality of product only be known after using
        it.
      - 3.It requires advance skills to fix.
      - 4.License prohibits you from modifying the
        product.
  - - - 1.Non-proprietary codes
        
        Some programmers are paid by non-profit company or by donations.
        
        Some programmers wrote for past time.
        
        Source codes are not secret. Can be registered as intellectual property.
      - 2.Can be freely used.
      - 3.Can be freely changed.
      - 4.Can be shared in modified and unmodified form.
      - 5.Made by many people.
      - 6.Can be freely changed.
    - - For computers
      - For mobile phone
    - - 1.Less hardware cost.
      - 2.Lower software cost.
      - 3.High quality software.
      - 4.No vendor lock in.
      - 5.Integrated management.
      - 6.Simple license management.
      - 7.Abundant support.
    - - 1.Cannot be learn in one day.
      - 2.Switching from proprietary to non-proprietary is difficult.
      - 3.Many hardware incompatible with open source platform.
      - 4.Most open source projects are being worked on by developers who do it for fun and in their own time.
      - 5.With the right knowledge it is quite trivial to find security problems in open source software, this can also lead to evil plan.
- - - - If it is, information used directly from the cache (fast)
      - If not, data copied to cache and used there
    - - Cache management important design problem
      - Cache size and replacement policy