The BASIC programs at this site have been tested on two independently developed BASIC interpreters, in an approach to perfect portability. Testing was done on a Mac, but the programs should work with most standard implementations of BASIC.

Compiler and interpreter. MacOS 8.6 to OS X. A Windows version is rumored to be in the works. Quirk/bug: Metal takes the whole CPU. The menubar and window location are locked while the program is running. Switching to the Finder and back to Metal blanks the terminal window; you can still type commands.

Interpreter. Runs on any MacOS, including 6.x; ported to OS X, Windows and Linux. Bugs/quirks: Sets the pointer to the Watch (telling you to wait for the computer) when you are not supposed to wait for the computer.

...tests and illustrates/practices a kind of reasoning. It's smarter than you.

...from liberal to conservative, totalitarian to libertarian.