Re: HP 30b RND function Message #3 Posted by Dieter on 25 Apr 2011, 8:36 a.m., in response to message #1 by Sujith Abraham
You will find the answer yourself once you realize that there are two different things here:
 On the one hand there is the number of digits the calculator is working with. This may be something like 10, 12 or 16 digits, depending on the model. The calculator always uses this many digits for all its calculations, and all results have this precision.
 On the other hand there is the number of digits you want to see in the display. If you set FIX 2 you tell the calculator "just show me two decimals  I don't need to know the rest". This display setting only affects the number of digits you see, while internally all values and results still have their full 10, 12 or 16 digits.
The round function now does this: it replaces the current fullprecision value by the rounded number you see in the display. In other words: before, the number only was displayed with two decimals, and afterwards it actually has only two decimals.
Assume the current value is Pi = 3,141592653589793238462643... and your calculator works with 12 digits. This is what happens:
 display set to 
FIX 2 FIX 4
now
you see 3,14 3,1416 press 3,1416
[RND]
calculator 3,14159265359 3,14159265359 => 3,141600000000
works with
So in FIX the round function rounds to the chosen number of digits behind the decimal point. In SCI and ENG it rounds to the number of significant digits you see. Finally try FIX 2, enter a value like 0,000004 and see what the round function does now.
Dieter
Edited: 25 Apr 2011, 8:39 a.m.
