A3Calc is a calculator program for Windows and SymbianOS platforms. The Windows version is "PostcardWare" and the SymbianOS version is commercial.
A3Calc is BASIC programmable. You can program your own functions and save the BASIC code in text files (*.BAS). No programming tools are needed; a text editor suffices. The same BASIC files work on all supported platforms.
You can customize A3Calc so that it automatically loads the BASIC files you need at startup. Also, you can attach functions and subroutines to function buttons, so they are readily available.
A3Calc is delivered with a collection of BASIC applications. Also, a comprehensive programming guide (and other documentation) is included.