xcalc
More info
- Creator
- John Bradley
- Type
- Calculator
- License
- MIT
- Source
- gitlab.freedesktop.org/xorg/app/xcalc
The X11 calculator, which imitates a Texas Instruments TI-30, or with -rpn an HP-10C with reverse Polish notation.
John Bradley at the University of Pennsylvania wrote the original for X10; Mark Rosenstein at Project Athena and Donna Converse at the MIT X Consortium reworked it for X11 and the Athena widgets. The default mode is a TI-30 with infix notation and parentheses; -rpn turns it into an HP-10C with a stack and an ENTER key, including a row of blank buttons that were programming keys on the original. The keyboard works as accelerators, so the calculator is usable without a mouse.
What makes it interesting is how it is built. The position, label and function of every key live in what the man page calls an "enormous" app-defaults file rather than in the C code, so anyone wanting a different calculator can write their own resource file without compiling. It is the Xt philosophy taken to its logical extreme: the program is an interpreter for its own configuration.