PREFERENCES :

Preface, you can only set preferences at runtime currently. I'll try to add reasonable saving of preferences in the near future. For now, there are nice defaults, and it's easy to change stuff.

Leading Operator: You see, there's this ambiguity about the minus sign. It means negative sometimes and subtract other times. If you put a leading sign into the Edit Field, it usually means that you want to add, subtract, whatever from the last answer. Sometimes you want to multiply (-5) with (-7). putting in a leading space or putting the expression in parentheses will make it a negative no matter the program settings.

As of v0.7.1 this ambiguity now applies to the plus sign as well.

Degrees / Radians: If you enter things in radians and want answers in radians, then alter the preference so that it uses radians instead of degrees.

Base - it's mentioned in it's own section. In short, change the base you are working in. Includes input as well as display.

What I Type / What it Means: In the display field, what you enter is displayed alongside the result for your viewing pleasure. It has been useful to show a bit of what the calculator is thinking when you type, say,
-0.5
but it can also make for clutter if you type, say (2#pi R^2)

Significant Digits - or more loosely, rounding. Affects display in editField and in main Display, in any base. The rounding is done logically in Base 10 however. Last Result remains 64bit accurate. Perhaps a transcript would help illustrate this point. The following was done with a rounding value of 9 significant digits:

1234567891 = 1.23456789e9
+5 = 1.2345679e9
-5 = 1.23456789e9
+1 = kf12oi (base 36)
+1 = kf12oi (base 36)
+1 = kf12oi (base 36)
+1 = kf12os (base 36)
+1 = kf12os (base 36)
+1 = kf12os (base 36)
+1 = kf12os (base 36)

If you have just evaluated an expression, setting the Significant Digits slider will change the display. For instance, if you had Significant Digits set to 3 and divided 8701 by 2 you'd get 4350. If you then slide the Significant Digits slider to the right a few places, the editField will then read 4350.5 thus revealing the more accurate answer.