This isn't something I found in the usual places so wanted to share here-- this is the 1978 GRT Corporation distribution of Microsoft's cassette BASIC for 6800, including the CSAVE/CLOAD and LPRINT commands. It was designed to target SWTPC machines. S19 file from a copied tape rip and manual scan of an old Xerox attached (I don't have access to originals of either). This is the post-Altair-680 BASIC that mholley/Mike D refers to on this page. I don't know if there was a cassette version for the Altair beyond the paper tape.

Anyway my interest was porting a usable cassette BASIC to my own Sphere system, which ended up needing some light reverse engineering in addition to standard terminal patch points. If anyone's curious about the rigamarole for an oddball platform, I have an archive incl commented asm listings and a README for the Sphere adaption on my Resources page (or direct link).

In any case, hope this is handy! If anyone knows any more historic context on this BASIC I'd be happy to hear that, too.

Ben Zotto

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Thanks for this José! The missing pages of the manual clarify that this is Ric Weiland's Altair 680 BASIC but "implemented on the SWTP 6800" by Mark Chamberlin (also at Microsoft). In addition to the parochial serial board autodetection stuff, it adds the line printer functions. I note that it removes Ric Weiland's author easter egg in favor of a generic Microsoft message. Beyond all that, the core of the interpreter may be no different/evolved from the earlier Altair versions.  

Was Microsoft still only working through OEMs/licensees at this point? GRT doesn't seem to add product value here, notwithstanding the marketing and retail distribution.