I'm looking into getting a PDA, specifically a Pocket PC, partly to program for. Searching around I've found that development on both Palm and PPC seems to be free, with Embedded VC++ 3 and 4 for PPC and various tool chains for Palm being freely available over the net. I'm looking for anyone with some experience with these devices. Specifically, how are the respective APIs? I'm guessing direct hardware access isn't allowed, aside from the CPU in user mode, and that everything else is done through provided APIs. Also, what I'd like to possibly attempt is writing a simple OS for one of these machines. Is it possible to build your own OS image to flash on to either a Palm or PPC? Do the images have to be signed in any way, or is it completely open? If this is possible, some detailed info on the memorymap, display, keypad, and touch screen, amongst others would have to be available, but I can't seem to find any. Any info or links is appreciated.

Yes it's possible to write an OS for the PocketPC. Why don't you look into how the PocketPC linux port did it? They obviously know how to do it :)

Check out the iMate, its a seriously kick-ass PDA running PocketPC

Thanks, the info I needed was here. Thanks for mentioning the Linux port, it helped in finding documentation.