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Palm OS

Palm OS. Frederick Penrose, Kevin Wong, and Hoan Do. Overview. Memory Management File System Demonstration. Memory Management. ROM vs. RAM. ROM nonvolatile memory stores key applications RAM dynamic & storage stand-by mode (power off) no hard drive

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Palm OS

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  1. Palm OS Frederick Penrose, Kevin Wong, and Hoan Do

  2. Overview • Memory Management • File System • Demonstration

  3. Memory Management

  4. ROM vs. RAM • ROM • nonvolatile memory • stores key applications • RAM • dynamic & storage • stand-by mode (power off) • no hard drive • What are the advantages of only using RAM?

  5. Dynamic RAM • size - depends on OS version, available RAM, software, stacks, etc. • dynamic heap • temporary storage for application • global variables, font tables, stacks & structures, library data, buffers (pen & key strokes), etc. • no write protection

  6. Storage RAM • stores application data & databases • persistent • contains one or more storage heaps

  7. Heaps • header • heap ID, status flags, heap size • master pointer table • dynamically built with persistent handles • maps location of each chunk

  8. Memory chunks • size: 1byte – ~64KB • movable • referenced by handles • location: beginning of heap • defragmentation • fixed • referenced by pointers • location: end of heap

  9. Heap Structure

  10. File Systems

  11. Original File System • records & memory chunks • database • no hierarchy • simplicity vs. organization • Why did Palm take this approach and what problems could they run into?

  12. Expansion Card • VFS (Virtual File System) • interfaces with other file systems

  13. New File System • NVFS (Non-volatile File System) • Tungsten T5 and Treo 650 • advantages • non-volatile • hierarchal file system • disadvantage • slower • fixed number of bytes

  14. Average File Size

  15. Demonstration

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