Palm Pilot and OS

1
Palm Pilot and OS

• PDA personal digital assistant
• Original Apples Newton Message Pad 1992
• Revival in 1997 Palm Pilot
• Objective of Palm
• Small, Light
• Simple Functionality
• Storage of written text address book
• Calendar, To do list
• Communication (email)
• Synchronization with PC

2
Implication on Technology

• Constant power supply from battery
• No Disk
• No Keyboard/Mouse
• No Floppy
• No Phone line or Ethernet
• Single user environment
• Almost single process

3
Example Palm i705

• CPU Motorola 33 MHz Dragonball
• Memory 8MB RAM and 4MB ROM
• Expansion Cards with applications
• Battery 1 week under normal use
• I/O
• Display,
• 7 button on front
• Pen and handwriting recognition
• Infrared
• Universal connector ( cradle)

4
OS Requirement

• Save Power Power Management
• Save Memory
• No Virtual memory since there is no disk
• Efficient allocation
• Input from Display support
• Security for email and other internet applications

5
Power Management

• Sleep Mode
• Either after power off or after a few minutes
  without input
• Display and Main clock shuts down
• Still alive real time clock and interrupt
  generator
• Wake up
• Interrupt from periphery
• Check battery
• Start Main clock
• Startup system parts

6
Power Management

• Doze mode
• Main clock is on
• LCD is on
• CPU does not perform any operation
• About 95 of none sleeping time

7
Power Management

• Running Mode
• After an interrupt the application is running as
  long as it takes to process users input
• Goes back into doze right after
• Each application works from event to event
• During wait for even it is either in doze or
  sleep mode
• Palm OS can go about 2 weeks for normal use
  before changing AAA battery

8
Data Management

• Files Systems Management is too inflexible for
  the small memory, moves files around
• Closer to databases than file systems
• Records (small pieces of data) are scattered over
  memory
• Every application has its own database
  (collection of records)
• Address size in Palm OS 3.X is 32 bit, word size
  from 8 to 32 bit
• 32 4G, much bigger address space than physical
• Palm OS 4 has Virtual File systems for
  compatibility

9
Process Management

• System is interrupt (event) driven
• There is no multi-process scheduling, rather
  batch type (switch between one application and
  OS)
• Processes are only started if they received an
  input event that call them
• Process runs until it is done (beware of infinite
  loops) or end process event happens
• OS takes over after finish and unless there is a
  new input interrupt is goes into doze mode
• Event Loop

10
User Interface

• Part of the OS
• No windows since display is to small for multiple
  windows
• Provides Input interfaces (similar to HTML)
• Scrollbars
• Menus
• Check boxes
• Text fields
• Popup lists
• Command button
• Applications create their own interfaces

11
Event Manager

• OS functionality that creates meaningful events
  out of basic interaction on the display
• Imagine you write a letter onto the display
• Handwriting recognition is part of the OS
  (Graffiti)
• The coordinates of the pen stroke are transferred
  to the recognition function of OS and the
  resulting Character is places as an event on the
  event queue
• Application reads event with the correct ASCII
  code

12
Application Startup

• Application starts when user or other application
  requires it
• Initialization
• Find corresponding database
• After startup application goes into event loop
  and reads top entry from the event queue (input
  events)
• Event Manager Creates events out of simple user
  interaction

13
Communication

• Support email but no attachments
• Infrared port for data exchange between Palms
• Some support cell phone functionality
• Support for integration of wide range of third
  party scheduling software and operating systems
  (Mac, UNIX )

14
Comparison Windows CE

• Example Palm size PC (bigger than Palm)
• Designed for many different systems
• Creates significant overhead
• Complexity makes it harder to program
• Stable and robust on bigger devices, but problems
  with memory and battery life on small
• Requires a lot of memory for OS alone
• Voice messages (require a lot of memory)
• Larger display depletes battery
• Requires a lot of battery power (less that 24h
  life)
• Integration only with Windows 95, 08 or NT 4
• Flash slot for memory extension (you need it)

15
Security of Palm

• With emails come malicious code threads
• 2000 appeared first Trojan Horse
• Originally there was no memory protection as in
  UNIX or NT
• No files also means no access code specification
• More recent versions have addressed this
• Biggest security problem Theft and Loss
• Dont store sensitive data on a Palm