palm os frederick penrose, kevin wong, and hoan do
TRANSCRIPT
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 What are the advantages of only using RAM?
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
Storage RAM
stores application data & databases persistent contains one or more storage heaps
Heaps
header heap ID, status flags, heap size
master pointer table dynamically built with persistent handles maps location of each chunk
Memory chunks
size: 1byte – ~64KB movable
referenced by handles location: beginning of heap defragmentation
fixed referenced by pointers location: end of heap
Heap Structure
File Systems
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?
Expansion Card
VFS (Virtual File System) interfaces with other file systems
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
Average File Size
Demonstration