Willis15C

Willis15C is a programmable RPN scientific calculator for people who think in Reverse Polish Notation and want to trust every digit. It computes in 10-digit decimal arithmetic, not binary floating point, so 0.1 + 0.2 is 0.3. Results round the way a classic scientific calculator rounds, across the full range from 1e-99 to 9.999999999e99. The math engine has been checked against more than 20,000 independently computed cases. A CLASSIC FACEPLATE A horizontal layout with a brushed-metal panel, dark bevelled keys, gold and blue shifted functions, and a seven-segment display with status indicators. Everything is drawn in code, so it stays sharp at any size. On iPhone it fills the screen in landscape. SEE THE WHOLE STACK Slide out the stack panel to watch X, Y, Z, T, LAST X, and the storage registers update as you work, including the imaginary stack in complex mode. ADVANCED TOOLS • Keystroke programming with labels, subroutines, loops, tests, and flags • SOLVE finds the roots of your own functions • Numerical integration of your own functions • Complex numbers, with functions that work on both parts • Matrices: up to five, with inverse, determinant, and solving linear systems • Statistics, linear regression, permutations, combinations, and random numbers • Hyperbolic functions, polar and rectangular conversion, and time and angle conversion • Built-in help, with worked examples for every part of the calculator BUILT FOR THE KEYBOARD On Mac, type digits and operators directly, press Return for ENTER, and open an on-screen key map any time. Copy and paste the X value. ALWAYS WHERE YOU LEFT IT Your stack, registers, programs, and settings are saved automatically, like continuous memory. PRIVATE BY DESIGN No account, no ads, no tracking, and no internet connection needed. Nothing leaves your device.