Palm OS

Christine Jones

CS 550 Section 1

Fall 2005

• About• Success of Palm OS• Handheld Constraints• Power• Memory Management• Chunks• Palm OS version 3.x• Palm OS 5• Palm OS Garnet• Palm OS Cobalt• Summary

About

• Palm 1000 debuted in 1996

• 70 % of handheld market

• OS– Versions 3.1, 3.2, 3.3 were developed for

specific devices– Beginning with 3.5, OS developed for use with

all Palm devices

Success of Palm OS

• Acknowledged differences between handheld device’s system needs and a desktops

• Simple

• Efficient

• Backwards compatible

Handheld Constraints

• Power

• Memory

• Screen

• Time (Speed/Efficiency)

Power

• Palm OS system is always on

• Three modes– Sleep– Doze– Running

Memory Management

• Chunks

• Dynamic Heap

• Storage Heap

• OS and built in apps stored in ROM

• User’s data and installed apps stored in RAM

Chunks

• Memory is divided into chunks and then allocated

• Have a max size of 64 kB

• Two types:– Handles– Pointers

Palm OS version 3.x

• Total Dynamic Memory Area = 96 kB

• Dynamic heap = 64 kB– System Globals = 2.5 kB– Application Stack = 3 kB– (if applicable) TCP/IP stack = 32 kB– Remaining memory <= 36 kB

Palm OS 5

• PACE

• Backwards compatibility

• Advanced RISC Machine processors

• Emulation Mode

Palm OS Garnet

• Based on Palm OS 5

• PACE environment

• Preemptive multitasking kernel

• User Interface Application Shell (UIAS)

Palm OS Cobalt

• ARM processor and PACE (similar to Garnet and OS 5)

• Difference:– Multithreaded applications

Summary

• Successful because of:– Efficiency– Attention to customer needs– Ability to evolve