joy of text
Editor with scripting language, security features & system interfaces.
... and textual data and reports from arrays of large text files.
It's adaptable user interface, can be programmed to emulate emacs , vi UIs or mouse-driven systems - but who would want to do a thing like that? The display is highly configurable supporting popups, menus-event mouse callbacks etc.
The jot language is terse, powerful and well supported, having a useful debugger and many diagnostic features. Importantly, no mode change is required to enter commands in it's native language.