The First Port

As of July 2nd, 2008, the Amortization Calculator was officially moved from its old location in the Meteorology Department of Florida State University to this website. The primary impetus for the move is that the aging machine on which the calculator had been running since the mid-90s will soon need to be shut down for good. In fact, running the calculator was about all the old machine had been doing for the last 4 or 5 years.

Since I had to recompile the calculator program as part of the move anyway, I took the opportunity to make a few little tweaks to the design, and to make a few minor bug fixes and enhancements. The biggest visible change is the addition of a Google ad bar, which I’m sure will annoy some folks (and I can’t say I love the look myself). However, where web and network services were provided to the world “for free” by the university, *I* am now paying so that folks can continue to have access to the calculator. I think it’s only fair.

So in case anyone is interested (and if you’re not, that’s OK: this is just a personal record of my work), here are some of the changes that I’ve made to the calculator while moving it to its new home.

General Changes

• If the calculator does not receive HTTP POST data, rather than complaining, it now draws the default web form. Previously, POST data had to have been received for the calculator to plot anything.
• I made some variables pertaining to errors global (versus local) so that error messages could be properly propagated and displayed to the user.
• The calculator now makes extensive use of CSS, which makes tweaking the layout so much easier. It also means that error messages are able to be displayed properly, in a nicer context.
• For consistency, the support pages (the FAQ and Info pages) use the same stylesheet, although their layout does need to be tweaked a bit more before I’ll be really happy with them.
• The source code has been refactored, especially as it pertains to web page output. It should be easier to make changes/additions to the calculator page now.

Enhancements

• I tried to make the error messages more explanatory, less computer jargony, and to perhaps assist the user in correcting an issue where possible.
• I added some additional calculations to the “Summary” section: the number of years is calculated from the total number of payments, and now the minimum payment required to amortize the loan is calculated. (Payments less than this amount do not allow for any principal reduction, and in fact, may cause unpaid interest to accrue into additional debt.)
• I trapped a few more error conditions, which might cause the calculator to provide misleading data in fringe cases. I thought of a few more conditions I can try to address some other time.
• The state of the “Show Amortization Schedule” flag is now maintained between invocations. Previously, the flag was purposely reset between invocations because of the extra processing load incurred. We have more powerful machines now, so who cares? 🙂

I probably left some things out, but I think I hit the highlights.