Latest version is 9.1b.  Download it here.  Fixed a bug with the "%" command regarding the stack.  Thanks to Christian K. for point this out.  Also added a few more keyboard shortcuts that he suggested.

 

Installation:  This is just a small, simple .exe file.  You can put it anywhere and run it.  I usually put it on the desktop.  I also make a shortcut to it then drag it onto the Windows "Quick Launch" toolbar, next to the "Start" button...

Previous version:   9.1a.  Download it here.  New option limits itself to one window, so you don't wind up with several instances of the calculator. Improved keyboard input and dialog box help that lists keyboard commands. Window can be "scaled" to make it bigger and it now remembers it's last setting. Registry location has changed from the default to "\Rayslogic" (so it may not remember your settings from the previous version).