Free42-Decimal

Free42 is a re-implementation of the HP-42S calculator and the HP-82240 printer.
It is a complete rewrite, not using any HP code, and it does not require an HP-42S ROM image.
Free42 Decimal uses Hugh Steers' 7-digit base-10000 BCD20 library, which gives 25 decimal digits of precision, with exponents ranging from -10000 to +9999.
The binary version has the advantage of being much faster than the decimal version; also, it is smaller and uses less memory.

However, numbers such as 0.1 (one-tenth) cannot be represented exactly in binary, since they are repeating fractions then: 1/10 is exactly 0.1 decimal, but 0.00011 binary. This inexactness can cause some HP-42S programs to fail.