Path: utzoo!attcan!uunet!aplcen!haven!decuac!shlump.nac.dec.com!jareth.enet.dec.com!edp
From: edp@jareth.enet.dec.com (Eric Postpischil (Always mount a scratch monkey.))
Newsgroups: comp.sys.handhelds
Subject: Re: Units Problems...
Message-ID: <15582@shlump.nac.dec.com>
Date: 25 Sep 90 17:38:22 GMT
References: <9682@ccncsu.ColoState.EDU>
Sender: newsdaemon@shlump.nac.dec.com
Reply-To: edp@jareth.enet.dec.com (Eric Postpischil (Always mount a scratch monkey.))
Organization: Digital Equipment Corporation
Lines: 34

In article <9682@ccncsu.ColoState.EDU>, jn190068@longs.LANCE.ColoState.EDU (Jay
Lewis Nestle) writes:

>	enter 1 degree C twice then add them, the answer
>	is: 275.15 degrees C
>
>	This is clearly wrong:  Either 275.15 K or 2 deg C
>	would be great, but it seems that the 48 is forgetting
>	to convert back to deg C but is informing the user 
>	that it has.  Bug!!!

This isn't wrong or a bug.  It is described in the manual.  See "Adding and
Subtracting Temperature Units" on page 201.

The Celsius and Farenheit scales are not zero-based.  That is, 0 degrees C and 0
degrees F are not really zero anything; they are just a position on the scale.

Whenever you add pure temperatures, the calculator adds absolute temperatures. 
It's equivalent to converting to kelvins, take the two numbers of kelvins,
adding the numbers, interpreting the sum as a number of kelvins, and converting
back to whatever scale.

If a unit contains a temperature but also contains other units (or contains only
temperature but with some exponent), the calculator will treat the temperature
as a relative temperature -- that is, as an indication of the difference of two
temperatures, rather than an absolute temperature.

To add x degrees C and y degrees C, you could add them and subtract 0 degrees C
or you could multiply them by some other unit, perform the addition, and divide
by the other unit.  (The second method works whether the inputs are Farenheit,
Celsius, or whatever.  The first requires you to know the scale.)


				-- edp