DB40X

DB40X is a high-precision scientific calculator compatible with DB48X and inspired by the legendary HP48 series from Hewlett-Packard.
It is not an emulator, but a redesign from scratch, which is faster, and delivers never seen before capabilities like computations in arbitrary precision.

Like the original HP48, DB40X supports an unlimited stack, RPN and algebraic operations, complex numbers, based numbers, vectors, matrices, text, symbolic computations, numerical solving and integration, graphing and plotting, statistics, engineering units, and well over 1000 built-in functions. DB40X adds several HP50G capabilities, including a library of equations and constants covering mathematics, physics or chemistry.

Using modern technologies, DB40X goes well beyond the original HP48 in many ways:
- It is significantly faster, uses less memory, and features a higher-resolution 240x400 pixels graphical display.
- Integer and decimal values can have an arbitrarily large number of digits, so you can compute log(pi) with 200 digits in a few keystrokes.
- The six function keys feature up to three function per key, giving quick access to up to 18 related functions at a time.
- Complex numbers can mix and match polar and rectangular form.
- Symbolic operations extend to complex numbers, vectors and matrices.
- Based numbers can be in any base from 2 to 36, and support any number of bits, making it easy to emulate a 23-bit or 512-bit processor.
- Text is represented using Unicode instead of the proprietary HP encoding, facilitating data exchange with the rest of the world.
- Multiple graphs can be distinguished using bitmap patterns.
- Engineering units include all the modern evolutions of the SI system, and can be configured by the user, e.g. to integrate currency units with the exchange rate du jour. Converting between USD/hour and EUR/day has never been so easy!
- A built-in hyperlinked help system documents functions simply by holding the corresponding key, and combine a quick start guide, a user manual and a reference manual.

DB40X will run many user RPL programs as is.
However, since it is not an emulator, it will not run any HP binary object, and notably will not run HP48 games or anything involving system RPL.

Version 0.7.14 is an early-access release. Please consult https://github.com/c3d/db48x/blob/stable/doc/5-Unimplemented.md for a list of HP48 commands that are not yet implemented.
DB40X is part of a family of compatible RPL calculators that include DB48X and DB50X.
DB40X lacks the ability to write programs or data to disk, and RPL programs are limited to 40K.

更新履歴
This version introduces the APPLY, SUBST, WHERE, CONLIB and EQNLIB commands, as well as an simpler way to enter an `=` sign in expressions. It improves the results given by the solver for functions with very large values.