[ILUG] handhelds/psion5 and linux

[John P. Looney]

On Tue, Jun 15, 1999 at 04:06:00PM +0100, sdempsey mentioned:
> What's the PalmOS file system based on anyway ?
> This may sound like a stupid question but apart from 
> the different hardware architectures involved , what is the main
> difference between a palm and a desktop OS ?

 Well, straight off, it doesn't have a filesystem.

 Everything is based around databases. Each application is a database that
happens to contain executable code, and uses databases that happen to
contain resources like icons, text, binary data.

 Something like the "memo pad", a text editor, creates itself a database,
and then each row is a "filename|type|contents|details|dates" type entry.

 Why is this good ? Well, if you 'load' a program, you don't do anything.
The executable code in the database is already in memory, so you just set
it running (in effect, the equiv of main() get's a '
sysAppLaunchCmdNormalLaunch' command - which means "Wake up, you are
running". It's a very rudimentary co-operative multitasking model. This is
mainly to keep it simple, and thus conserve battery power - an app that
isn't doing anything keeps control of the CPU - until an interrupt comes in
- and just powers down the CPU till an event is raised.

 Also, because you are not tied to the old idea of a tty, you have a
180x180 display that means text-based programs, and windowsCE like
windowing gadgets aren't really possible. Sure, there is plenty of text
input and output, but the gadgets etc. are designed for a small screen, so
they are exceptionally neat. Not pretty, but they don't need to be.

 Any other questions, I'll do my best to answer them, and if I don't know,
I'll guess ;)

Kate

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