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CHAPTER 1: INTRODUCTION (COMPUTER SYSTEM ORGANIZATION (Interrupt (How it…

- - - - define ways resources are used to solve user's computing problems
        
        word processor, spreadsheets, web browser
    - - controls the hardware and coordinates its use among various application program and users
        
        windows 10, linux, unix
    - - provides basic computing resources for the system
        
        cpu, memory, I/O devices
  - - - One user (PC)
        
        goal is to maximize work that user is performing and for ease of use with some attention paid for performance.
      - Multiple user (mainframe)
        
        goal is to maximize resource utilization to assure they are used efficiently
    - - resource allocator
        
        os acts as the manager of the resources and it must decide how to allocate them to specific programs
      - control program
        
        os manages the execution of user programs to prevent error and improper use of the computer
- - - - hardware
        
        triggers any time by sending a signal to the CPU usually by system bus
      - software
        
        executes a special operation called as system call or monitor call
    - - must transfer control to the appropriate interrupt service routine
      - save the address of the interrupted instructions
    - - when cpu is interrupted, it stops what it's doing and immediately transfer execution to a fixed location
      - fixed location contains starting address where the service routine for the interrupt is located
      - interrupt service routine executes on computation the cpu resumes the interrupted computation
    - - In interrupt, the device notifies the CPY that it needs servicing whereas in polling cpu repeatedly checks whether a device needs servicing
      - An interrupt can occur at any instant if time whereas cpu keeps polling the device at the regular intervals
  - - - higher levels are expensive but they are fast
      - storage system above SSD are volatile and SSD and below are non volatile
  - - - To solve problem of moving bulk data that's going to cause large overhead in I/O operation
    - - device controller transfers an entire block of data directly to or from its own buffer storage to memory with no intervention by the CPU
      - only one interrupt is generated per block to the device driver that the operation has completed rather than one interrupt per byte
      - while device controller is performing these operations, cpu is available to accomplish other work
- - - - one main cpu capable of executing a general purpose instruction set including instructions from user processes
      - cons
        
        run a limited instruction set and dont run user processes
        
        os cant communicate with these processors as they do their job autonomously
    - - It has 2 or more processors in close communications and sharing resources
      - pros
        
        increased throughput
        
        by increasing the number of processors, users expect to get more work done in less time
        
        economy of scale
        
        it can cost less than equivalent multiple single processor system
        
        increased reliability
        
        failure of one processor will not halt the system only slows it down
      - Types
        
        asymmetric multiprocessing
        
        each processor is assigned a specific task. it has boss worker relationship in which the boss processor controls the system. other processors either look to the boss for instruction or have predefined task
        
        symmetric multiprocessing
        
        each processor performs all tasks within OS and all processors are peers
        
        pros
        
        many processors can run simultaneously without causing performance to deteriorate significantly
        
        cons
        
        cpus may stting idle while another is overloaded resulting in efficiencies
      - multicore
        
        multiple cores on a single chip in which can be more efficient than multiple chips with single cores
        
        pros
        
        on chip communication is faster than between chip communication
        
        one chip with multiple cores uses less power than multiple single ocres chips
    - - another type of multiprocessor system but they are composed of 2 or more nodes joined together. They share storage and are closely linked via LAN
      - type
        
        asymmetric clustering
        
        one machine is in hot standby mode while the other is running the apps. If the server fails, the hot standby host becomes the active server.
        
        symmetric clustering
        
        2 or more hosts are running apps and monitoring each other. More efficient as it uses all hardware
- - - - ultilized efficeintly
    - - dont provide user interaction with computer system
- - - - stand alone general purpose machine. all the system processes are available on the computer and executed there
    - - refers to computing handheld smartphones and tablet computers. portable and lightweight
    - - contains multiple nodes that are physically separate but linked together using the network
    - - a networked computing model that distributes processes between client and servers which supply the requested service
    - - another structure for a distributed system. clients and servers are not distinguished from one another instead all nodes are peers
    - - allows os to run as applications within other OS
    - - it delivers computing, storage and even applications as a service across a network
    - - well defined, fixed time constraints processing must be done within the define constraint or system will fail.