HP calculators don't handle 'true' HMS representation Message #17 Posted by Vieira, Luiz C. (Brazil) on 15 Aug 2004, 2:37 p.m., in response to message #2 by Andrés C. Rodríguez (Argentina)
Hi Andrés, Juan, all;
Andrés, you touched a very sensitive point: HMS true representation.
I remember seeing many other calculators with [º'"] key, not available in most HP calculators, that would allow HMS to be entered "as is". Almost all HP calculators (if not all "true" HP-designed calculators) and almost all TI till the 90's take a decimal number in the display and return a decimal number to the display, they never take an HMS representation and return another HMS representation. So, Juan Miguel, .316000... is .316000... and it is correct, but the calculator does not "see" .316000... as if it is 0º31'60", what is actually 'wrong' (not much wrong, maybe). And again Andrés shows the "backstage" of the actual number: .3159999... This number correctly rounds to .316000..., because the calculator does not recognize an HMS representation. This would never happen with an HP30S or an HP9G, because these newer "HP" calculators can handle these figures the way Casio and others do.
A related situation can be found with the HP12C and some others (HP41CX, HP48/49 series) when dealing with dates and date representation. When you key in 4.022004 in any calculator, this is only 4.022004. But if you want any of the calculators above to handle this number as a date, check if the calculator is set to D.MY or M.DY (all of them do that) prior to use 4.022004, because the calculator can take it as February, 4th. 2004 or April, 2nd. 2004. But, hey! This is just a number! What if I key in 25.132004? If I plan to use it as a date representation, it is already wrong in any date mode (no such 13th. month), but if I key it in, the calculator cannot complain untill I tell it what to do with the number.
I know we are talking about resulting values, and this is different of keying in values. But if we see somethnig that seems to be wrong as a resulting value, let's see if the calculator sees it as a wrong input data. Try this in any HP calculator:
12.65 ->HR (in some models, it is HMS->
Well, what is wrong? I'm telling the calculator to return the decimal equivalent of 12º65' !!!! And it does not complain, you see? 12.65 is a valid number, and it promptly gives you a correct answer - 13.08333 - because sixty five minutes is something that actually exists. Now try to bring back the original value:
->HMS
Yeap! There it is! 12º65' atually is 13º05'. I am completely aware and conscious about internal rounding and precision, but when dealing with HMS and decimal representation, I have my own additional concerns.
Any comments?
My 1¢.
Luiz (Brazil)
Edited: 15 Aug 2004, 2:48 p.m.
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