My favorite computer program is FileMaker Pro, a database manager from FileMaker Inc. (FMI), a wholly owned subsidiary of Apple. Not least of its many virtues is that it's 100% cross-platform compatible between Mac's OS X and Microsoft's Windows. You can create a database system on either platform and copy it over to the other platform, and it'll work 99% the same. (There are some annoying font-sizing differences due to Windows being less efficient at using space than the Mac.)
And now FMI has made the leap to iOS as well. That's the operating system that Apple uses for its hand-held devices, the iPad, iPhone, and iPod Touch. Since iOS devices are mainly intended for consuming information, not creating it, there is no version of FileMaker Pro itself that works on them (at least not yet). What you get instead is something called FileMaker Go (not Pro). The bad news is, as mentioned, that you can't use it to create new databases; you can only use databases created on a regular computer using FileMaker Pro. The good news is that FM Go is free. You can readily download it from the FileMaker website.
My first project for FileMaker Go was to modify an existing database, Music Library, that I'd created for Madison Youth Choirs so that a person holding an iPad in one hand could rummage thru the library (multiple shelves in their own room) looking for appropriately themed music and tagging on screen the scores they were interested in. I won't go into all the detail here of what sorts of modifications were needed, but suffice it to say that a touch-based interface requires some substantially different approaches than a mouse-and-keyboard-based interface.
Still in all, the redesign went pretty smoothly until I got to what I figured would be the easy part: copying the database file over from my Mac to the iPad. And it turned out not to be easy (or intuitive) at all! So, after I tapped into the brains of people more knowledgeable than I, I had 3 different techniques that would work. In order to provide documentation for future users (mainly the me of 10-12 months from now), I wrote up my findings in the form of a couple of explanatory screens right within the database file itself. I herewith make them available to all (click to enlarge):