If you're on Windows and are just looking to write a program
Microsoft invented something much like AIR about 8 years ago called
HTML Applications (
It's basically a web page with one special tag at the top to set
some application-like properties for the main window, named with a
.hta suffix so Windows knows to open it with IE.
The technology hasn't moved forward since the days of IE4,
except of course that the base rendering engine has gotten a lot
more powerful. You also lose out on cross-platform compatibility,
and to get the single-file download-and-install behavior you get
for free with AIR, you'll have to separately build some kind of
installer, like an MSI. In an HTA, all of IE's security features
are turned off, so you can do things like access COM objects to use
more powerful APIs than a web app normally has access to. Through
that interface, you can do all the same sorts of local file and DB
access that AIR can do.
Bottom line, you can think of HTAs as "AIR Lite for Windows".
AIR is portable and, on the whole, a lot more powerful, but if you
can tolerate its limits, it can be a good solution.