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About this app
Plus42 is an advanced scientific programmable calculator, based on Free42. Free42, in turn, is a complete re-implementation of the HP-42S scientific programmable RPN calculator, which was made from 1988 until 1995 by Hewlett-Packard. Free42 is a complete rewrite and contains no HP code whatsoever. Plus42 builds on Free42 and adds: Algebraic expressions modeled after those used on the HP-27S and HP-17B/19B; attached units and unit conversions modeled after those used on the HP-48/49/50 series; directories for more organized storage of programs and variables; a larger display, with 8 rows and 22 columns (131x64 pixels) by default, which the user may resize at will; time value of money and amortization schedules; and two-dimensional plotting of functions, with ability to zoom and pan, and find integrals and roots from points in the plot.
What's new
Version 1.5.2 · Nov 5, 2026
Implemented ARG. When using LTOP and ATOP options together, to show both the LASTX and ALPHA registers at the top of the stack area, the user can now control the order in which they appear: whichever one was enabled most recently will be above the other. Implemented conversions to and from DPD-encoded decimal floating point: N→PS/PD/PQ, PS/PD/PQ->N. Fixed two-argument STOFLAG. It got broken in 1.5. Fixed pasting of HP-41 style GTO/XEQ IND X/Y/Z/T/L.
