Is this an overflow error, and if so, what the heck?

Projects Programming
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Hello,
I'm a bit of an arduino & programming noob. I did some searching on the forum and with google, but I don't think I can put my question/situation in good enough terms for a search engine, so here I am.
I'm using the code from here - http://arduino.cc/en/Tutorial/PachubeClient - with some minor, I think, modifications. Basically, I've commented out the DHCP part, and am using a static ip.
Everything works fine, but I don't need updates every 10 seconds, as this line does

const unsigned long postingInterval = 10*1000; //delay between updates to Cosm.com

So I changed it to const unsigned long postingInterval = 60*1000; //delay between updates to Cosm.com to give a one minute (60 * 1000 millis = 60,000 millis, right?) delay, but it doesn't work.

So, I added some debugging lines serialprint(postingInterval); and found that the value of 'postingInterval' was 4,294,941,790, not 60,000. Hmmm, that's roughly 2^32 which is the storage space for the 'long' data type, so I thought I'd try some other values.

Any integer up to 32 const unsigned long postingInterval = 32*1000; would give an expected value (for 32, 32000), but an integer of 33 or greater returned that 2^32 value.
Trying decimal numbers, 32.999 returned 32999 and 32.999999 returned 33000.

Well, how about trying? const unsigned long postingInterval = 60000;
That works fine; returns 60000, and gives me my 1 minute update, so everything is going well.
Except, I don't know what's caused this error.

I'm not looking for a handout here, but if someone can steer me in the general direction so I can figure out what's going on, I'd appreciate it.

I ran across something that seems similar to this years ago when I was working on my Master's thesis (Civil Engineering), and I had written a little program in FORTRAN, and was getting different results depending on whether I had a debugging line or not. At that time, it was apparently due whether the value had been placed in memory or not; I can't recall for sure.
I have to say, though, that programming with concrete is a little easier than FORTRAN...

Thanks

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The value stored in the variable has a direct relationship to the value stored in a register as a result of a calculation. The type of register that the calculation is performed using has NO relationship to the type of value that the result will ultimately be stored in.

60 is an int. 1000 is an int. Multiply them, and you have overflow.

60L is a long. 1000L is a long. Multiply them, and no overflow occurs.

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@PaulS

Thank you very much - It works as you said. I have learned something here.

Now, let's see what other noob mistakes I can make :roll_eyes:

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Now, let's see what other noob mistakes I can make

Come on back when you do. We all love a good laugh. 8)