systems software

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  • Created by: jacksie
  • Created on: 04-11-19 10:52
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  • software systems
    • operating systems
      • user interface
        • an environment for a user br to interact with the machine
        • GUI
          • text, and icons
          • interacts with a mouse and keyboard
          • Don't need to program any commands personally
        • CLI
          • command line
          • text only interface
          • outputs response in text
          • needs knowledge of the codes of a particular machine
          • faster, more flexible, less memory
      • managing the Cpu
        • when the OS runs  piece of software it has a certain procedure
          • 1. has to find the program from the storage drive
            • 2. A section of RAM is reserve for the program and space allocated for the data
              • 3. Program is copied from storage into the reserved space
                • 4. the CPU program counter is set to the location of the instruction, and execution begins.
      • management and multitasking
        • multitasking, only works by allowing programs to run side by side
        • only works if there is enoughg memory
        • Paging
          • pages are fixed bloxk sizes of memory
            • usually 4KB
            • the OS sees how large the memory is and breaks it down into enough pages to hold it
          • pages may not be contiguous
            • but the computer knows which page hold which data fetches only necessary data
      • peripherals and drivers
        • Each peripheral device has its own machine code
          • this dictates how it transmits data
            • this is the protocol of controlling and communicating with a device
        • OS uses drivers to manage connections with peripheral devices
          • Drivers handle the translations of requests between a device and a computer
            • defines wehere a process puts outrgoing data before its sent, and where recieved data is stored
              • It wakes up the device and pouts ity back to sleep
                • peripherals with the same protocol can be controlled by the same driver
    • Utility software
      • encryption
        • encryption scrambles the contents of the file, so it appears to be gibberish
        • It uses a complex special algorithm
        • Allows only authorised usert unscramble content
        • end to end
          • whatsapp
            • each user has a special key
              • impossible to hack
      • when data is stored on a hard disk
        • it is stored as a series of segments
        • sometimes  the segments are in sequence but sometimes aren't this is called fragmentation
          • Fragmentationj makes the file harder to read from and write to
          • defragmentaion software, rearranges the segments so they run contiguously
            • this speeds up computer speed
      • compression software
        • this reduces the size of the files
          • this allows transmission to be quicker as they require fewer packetsto be sent
        • lossy
          • lossy compression reduces the size of a dile bygetting rid of data
            • reduces colour depth of photos
            • effective
          • JPEG
          • MPEG
          • MP3
        • lossless
          • some files we would not want to loos data
            • PDF
            • GIF
          • RLE- counta runs of data
            • what the data is and hgow many times in succesionj it occurs
      • Data Backups
        • data can be lost or hacked
          • to combat this copies should be made
        • Networks use backup software, to backup copies at a scheduled time of the day
        • backups are usually stored to a high capacity secondary stotage, orthe cloud
        • there aretwo types of backup
          • full
            • A full backup involves making a copy of every file on the computer or network. They can require a lot of storage space and can be time consuming to make.
          • incremental
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