PalmOS Version-o-Rama
Continued from Previous Page
A more critical change affected how working memory (see
@TEAL Issue #2) got allocated for the current
application. Under OS 3.0, the amount was fixed at 96
kilobytes. Under 3.5, this was changed to vary
depending on total RAM: 256kb for a device with 4Mb or
more of total memory, 128kb for 2Mb or higher, or only
64kb for a handheld with less than 2Mb of RAM. This
means that for most devices, programs typically have
more memory to work with at the expense of some file
storage space. Because of this, a few programs designed
to run under OS 3.5 may not have enough working memory
to run properly on older versions of the operating
system. Other internal changes, however, caused headaches for
developers (like us) at the time. OS 3.5 changed
slightly how applications interact with the display
screen and interface controls, and many programs needed
to be updated to maintain compatibility with the new OS.
At this point, virtually all developers who support
their programs have now fixed any problems, but there
may still be issues with older freeware or shareware
programs that have not been updated in the last year or
two. PALM OS 4.0
The newest kid on the block is OS 4.0, which came out
this spring on the new m500 series organizers from Palm.
Like moss to a stone that isn't going anywhere, many of
the new features in this release have been gathered
externally. Included is a new Telephony library to
provide a common software interface to integrated phones
and phone peripherals, services once specific to devices
like the Kyocera SmartPhone and Handspring VisorPhone.
Also included is the new Attention Manager, which allows
the user to view and manipulate upcoming timed events.
Perhaps the most important update to OS 4.0, however, is
the addition of the new Virtual File System (VFS)
library. This system, appearing first on the Sony CLIE
for their Memory Stick add-ons, provides a standard
interface for the system and apps to talk to external
storage devices like Smart Media cards, Compact Flash,
and SD/MMC flash cards. With a standardized interface,
software developers can finally design applications to
take advantage of add-on storage devices without having
to write separate code for each manufacturer's device.
VFS compatibility also comes standard on the Sony CLIE
and HandEra 330, and can also be added separately to
some devices as a software library in development by
Kopsis Engineering (www.kopsisengineering.com).
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