Many moons ago I got my first home computer: an Apple ][c. Included with my shiny new Apple were a set of disks with demos, guides, and utilities, many of which were written in AppleSoft BASIC. The interactive capabilities of BASIC were pretty rudimentary, and on these disks there were BASIC programs that seemed to be doing more.
So I took a look at the source code for these programs and lo and behold, Apple had built themselves library of custom BASIC commands that were tied to the & character (so instead of using INPUT they would use &INPUT and so on). This custom library was a simple binary file, and if you loaded that file into memory you could use the nifty new commands in your own programs. This added a lot of polish to what were otherwise simple BASIC programs. Other programmers learned about this, and soon many libraries were available with custom BASIC commands.
Fast forward to today. Apple has just released their iPad. The iPad comes with a Safari bookmark for the User Guide, which opens as a web application in Safari. And like the old disks included with the ][c, this guide seems to do some pretty amazing things for something done entirely in HTML, CSS, and JavaScript.
Turns out that once again Apple built themselves a custom JavaScript library for this app, and someone has already found it:
http://almost.done21.com/2010/04/adlib-apples-secret-ipad-web-framework/I hope Apple will release this library for public use. It would be awesome. Even if they don't, like the old BASIC library this new library shows what's possible.