It contains the usual decimal and logical functions as well as constants and conversions.

Features:
- BIG buttons.
- Simple to use.
- RPN input method. Two line visible stack.
- Basic arithmetic operations.
- Different display modes (Auto, Fixed, Scientific, Engineering) with possibility to choose number of decimal places.
- Different bases (Dec, Hex, Oct, Bin) with possibility to choose between 8, 16 and 32 bit 'word size'.
- Deg and Rad angle modes.
- The usual stack operations (drop, swap, clear) including undo.
- Arithmetic functions.
- Logic functions.
- Statistics functions.
- Combinatorics functions.
- Date and time functions.
- Conversion mode, including user conversions.
- Currency conversion with daily rates from The European Central Bank.
- Constants library, including user constants.
- Short and long display modes in constant library with possibility to show value.
- Quick constant and quick conversion function.
- Colour coding.
- Stores last settings.
- Optionally stores the stack.
- Regional settings aware (decimal point symbol and thousands separator).
- Square screen support.
- 800x480 screen resolution support (HTC Touch HD, Sony Ericsson XPERIA X1).

More screenshots here.

Compatible with QVGA and VGA devices, portrait or square screens (landscape screens are not supported).

YaRPNcalc HD v1.2:
For HTC Touch HD and Sony Ericsson XPERIA X1 (800x480 screen resolution), please download this software here (127 KB) or its mirror here.

Update Description:
v1.6.1 (22-01-2009):
- Fixes 'YaRPNcalc doesn't scale on VGA devices'. No need to update from 1.6 if your device doesn't have a VGA screen.

v1.6 (06-12-2008):
- Currency conversion with daily rates from The European Central Bank (see User guide for more info).

v1.5.5 (01-12-2008):
- Added support for 320x320 square screen Pocket PCs (e.g. Palm Treo 800w).
- Fixed 'repeatedly typing same digit is slow'.
- Cosmetic changes on the buttons.
- New icon.
- Note: .NET Compact Framework 2.0 is now required. This is already installed on all Windows Mobile 6 devices.

v1.5.4 (21-12-2007):
- Added Last X.
- Fixed crashes when using the time / date functions with very large (invalid) numbers.

v1.5.3 (05-10-2007):
- Fixed freeze when switching to engineering mode with number 0 on the stack (again).
- Fixed crash when starting YaRPNcalc in Landscape mode.

v1.5.2 (31-05-2007):
- Implemented time and date functions.
- Implemented user function layouts.

v1.5 (24-04-2007):
- Implemented different function layouts.
- Implemented 2^x function.
- Fixed crash when using 'Rotate stack' with too few arguments.

v1.4.2 (01-04-2007):
- Implemented support for square screen Pocket PCs (e.g. Treo 750).
- Implemented 'Rotate stack'.
- Fixed a wrong bitrate conversion factor.

v1.4.1 (02-03-2007):
- Made loading user conversions file more robust.

v1.4 (25-02-2007):
- New UI look.
- Delta % function.
- All HEX digits keypad.

v1.3.3:
- Fixed freeze when switching to engineering mode with number 0 on the stack.

v1.3.2:
- Implemented culture specific decimal point symbol and thousands separator. The decimal point symbol as well as the thousands separator now depend on the 'Regional Settings' set on your device.
- Fixed a bug in the menu code.

v1.3:
- Changed the way the menu buttons work. It's now no longer necessery to switch to the Conversion mode to do conversions. Instead, to make a conversion, just press the right menu button twice. For constants, just press the left menu button twice.
- Implemented a tool to create an up-to-date currencies conversion file.

v1.2:
- Implemented user conversions.
- Implemented user constants.
- Implemented smaller font on stack display for 32bit binary numbers (complete number now visible).
- Changed constants and conversions files from xml to non-xml which makes them smaller and improves startup time (somewhat).
- Fixed some bugs; my favourite being: -'123.4 (1000's separator on negative numbers).
- Made some minor cosmetic changes.

v1.1:
- Implemented new functions: coordinate conversions (polar <-> rectangular), absolute value, hyperbolic functions, permutation, combination, sum, mean, median, variance.
- Implemented 1000's separator.
- Implemented 'show values' display mode for constants.

v1.0:
- Implemented UNDO of last stack operation.
- Stack can now be saved on exit (as an option).
- Fixed a minor bug and made some other minor changes.

v0.9:
- Implemented engineering mode.
- Conversions are now loaded from conversion.xml.

v0.8:
- Implemented constants, including the QuickConstant function (last constant used)>
- Implemented custom buttons which can draw two lines of text as well as indicate an 'active' button by drawing a thick upper and lower border. This saves precious horizontal space.

v0.7:
- Implemented logic functions.
- Under the hood: started moving panel code out of MainForm code to allow usage of custom controls. What I want is a nicer possibility to show the active state on buttons (what I'm doing with [] at the moment) and the possibility to have two line labels on buttons.

v0.6:
- Implemented different integer mode precisions (32bit, 16bit, 8bit). Note that the OCT mode does not yet support negative numbers.
- Rearranged buttons on the Conversion form.

v0.5:
- Implemented factorial function.
- Fixed a bug which made the error messages not show up anymore.
- Fixed a bug where the new fast convert function did not first accept the current input to the stack.

v0.4:
- Regrouped buttons on Main menu form.
- Colour coded the different groups of buttons for better usability.
- Implemented conversion mode. some standard conversions are implemented, user conversions will come in a later version.
- HEX, OCT and BIN numbers are now 32bit. I'll maybe offer the possibility to go to 16 and 8 bit as well. Still no solution for the display width problem though.
- Implemented fast convert. when changing back to DEC mode from CONV mode, the Function form will offer the last conversion on a dedicated button.

v0.3:
- [ ] are used to indicate which mode is the active mode on the Menu form.
- The different settings are now stored in an .xml file which is in the same directory as the main executable, but not yet the stack.
- All the bases are now implemented (also Oct and Bin), but with restrictions. The display is too small (or the font too large) to show 32 bit in binary mode. I don't know how to 'fix' this yet. Converting negative values to Oct, Bin is not implemented yet. Converting negative values to Hex converts to 64 bit, which should probably be restricted to 32.