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          ＣＰＵ      function key
     ╭───┼──╮  ／    floppy disk      雜誌←Supplemental Data
     ╰┬──┼─┬╯↙  ↙     ┌───┐ ──────
main   ∣﹏╭╮﹏├╗┌┐       ∣衛生紙∣←Application Software
storage→┌╰╯  ∣  ∣∣       └───┘
       ∣∣∣  ↓∣  ∣∣Input       user interface          Debugging
       ∣∣∣  ↓∣  ∣∣  ↓        ↙   secondary            Tool
       └┼┼┬┼┤  ├┴─────┐     storage      Backup   ↓
 ──┬┬┘∣∣↘└─┴─────┬┘         ↓      System   ┌┐
 ──┼┼─┘└╮╰Data Flow╮ ／          ∣ 垃 ∣  ∣ ↓ ∣  ∣∣
↑   ┴┴      ╰╮╭◣Bug◢╯∣           ∣ 圾 ∣  ∣ 水 ∣  ∣∣
∣surge control  ∣↓Output   ∣←Hardware ∣ 筒 ∣  ∣ 桶 ∣┌┘└┐
∣   device      ┴─────┴～～～～～─┴──┴─┴──┴┴──┴
Network                            ↑Overflow(Input/Ouput Error)

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