Thursday, August 11, 2005


Just When I Thought That I Was Out...

I thought I was finished with the coin acceptor. We can insert 1-Euro and 2-Euro coins, with a better than 95% acceptance rate. One of the hardware guys came over and installed a newer model of the acceptor, and it worked too. I had mentally checked "coin acceptor" off my list of worries.

Then, in the late afternoon, another programmer comes into my office with more coins to test. But they aren't 1-Euro and 2-Euro coins—they are 5-cent, 10-cent, 25-cent, and 50-cent coins. "They told me to test these too. These will work, right?" he asked.

No! Of course they won't work. The documented requirements were that the coin acceptor should accept only 1- and 2-Euro coins, so it accepts those and rejects the rest. It's not supposed to accept anything smaller than 1-Euro.

Or is it? After some checking with the higher-ups, it turns out the answer is "maybe." Apparently somebody promised a French customer that smaller coins would be supported.

It was a surprise, but it won't really a big deal if "maybe" turns to "definitely." Enabling acceptance of the smaller denominations should be easy, and I can probably hand that work off to somebody else. The bigger issue is that this vending machine has never had to deal with amounts smaller than a whole dollar or whole Euro before, so some testing and tweaking will be needed to verify that all the displays and printed reports handle fractional amounts properly. The software has always done its internal accounting in cents, so we don't expect problems, but you never know what problems will arise with something like this.

Technical issues aside, it is going to be annoying if the machine has to accept different sets of Euro coins in different countries. Everybody is going to be confused, and I'm going to be fielding a lot of bug reports saying that such-and-such coin isn't working in such-and-such country. It would actually be easier for me if each country had a different currency.

By the way, if you were wondering, one one-hundredth of a Euro is officially called a "cent," or "Euro cent" if you need to avoid ambiguity. I understand that Europeans use many slang terms to refer to them; I'm using a few terms of my own.

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