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