When Floating Point Mode is selected, the base input is disabled. This is because these two are mutually exclusive to each other. The calc has two modes binary and floating. When in binary mode, all operations are performed using 32bit binary numbers and numbers are displayed and entered in the base selected. When in floating point mode, operations are performed using the Pilot's built-in floating point library.
Binary mode uses whole integer values as opposed to floating point mode where you can enter a decimal point (fractional value).
Selecting Unsigned Results causes the binary result to be displayed as an unsigned integer. All 32 bits of the result will be converted to a positive value. The default is to show binary values with the high-order bit representing the sign of the result.
Display Floats in Hex checkbox causes the all floating point results to be displayed in their hexadecimal form. This option only has relivence only on the PalmPilot since only this device uses the IEEE 754 format for floating point. And then, only to those programmers involved in understanding the floating point format.
Variables are Case Sensitive is the default and any variable defined or used is case sensitive. Unchecking this causes variables not to be case sensitive. For example, there is a variable called Disp that represents the current value of what's displayed on the calculator. You could enter this variable as disp if this checkbox is unchecked.
Mode selects the angle mode for Trigonometric functions and only has meaning if MathLib is installed
Rounding selects the current rounding mode and has meaning only on PalmPilot devices