Russell's BASIC is supposed to be as close as possible a copy of the BBC Second Processor system BASIC, which was v4 (v1 was the rather buggy version in the 198

Russell's BASIC is supposed to be as close as possible a copy of the BBC Second Processor system BASIC, which was v4 (v1 was the rather buggy version in the 1981 Model A, v2 the bugfixed 1982 Model B, v3... don't know, probably the almost unheard of B+, and v5 was the hand-tooled and significantly improved ARM version for the Archimedes line of computers). I believe the on-disk representation is compatible with Acorn's version. Incidentally, the BBC Micro had a real operating system, and a lot of BASIC functionality just shelled out to the OS. Russell's Z80 version replicates a lot of this itself, so commands like LOAD and SAVE to load and save raw memory will just work. EXEC, which reads console input from a file, and SPOOL, which writes console output to a file, both work too, which means converting to and from text is easy. Of course, none of the graphics primitives work, but all the hooks are there if you want to extend it! If anyone's interested in what BBC BASIC looks like, a little while ago I managed to recover a program I wrote in it in 1991. It uses graphics so I haven't tried it on the Z80 version, but it's interesting to look at nevertheless; and there's an emulator too: http://cowlark.com/2015-02-03-bbc-micro http://cowlark.com/2015-02-03-bbc-micro