programming-for-dummies

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Cross-Platform Programming
Unfortunately, the software as service model has two drawbacks. If you aren’t
connected to the Internet, you can’t use any software as service program. So if
you use a word processor over the Internet but take your laptop computer on
an airplane with no Internet connection, you can’t use that word processor.
A second problem with the software as service model is that using it constantly
costs money. Most software as service programs charge a monthly fee, which
gives you the right to use the program for that month. Although this monthly
fee is nominal (such as $5 a month), the cost can add up. Buying a simple
word processor might cost you $50. Using a word processor as a software as
service model might cost you $5 a month, so after ten months, you could’ve
just bought a word processor instead.
For each succeeding month, the cost continues, so you’ll wind up paying
several hundred dollars just to use a single program. For large corporations,
the software as service model can make sense. For individuals, the software
as service model is too expensive.
To eliminate monthly fees, software as service companies are offering their
programs for free but earning profits by selling advertising. Seeing advertisements
may be a minor annoyance, but it makes software as service available
to everyone, although there’s still the problem of not being able to use a program
without a constant and reliable Internet connection.
Rich Internet applications (RIA)
Rich Internet applications (RIAs) overcome the problems of the software as
service model by creating a program that’s stored on your computer but can
update itself over the Internet. RIA programs combine the ideas of virtual
machines with software as service.
Like a virtual machine language, RIA programs need a special virtual machine
for each operating system. This gives RIA programs the ability to run on multiple
operating systems. Because RIA programs are stored directly on your computer,
you can use them any time without an Internet connection and you aren’t
locked into paying a monthly fee to access the software. Like the software as
service model, RIAs can connect to the Internet and update themselves to
insure that you’re always using the latest version.
One popular RIA programming tool is Adobe AIR, which combines the languages
of Web page designing (HTML and Flash) with scripting languages
(JavaScript) to run on multiple operating systems through a virtual machine
(like Java).