I'm not a mac user anymore. But I used to be one when I was a kid. My father had a Macintosh Performa 6200 running MacOS 7.5.3.

On said MacOS you could press command + the turn on key on the keyboard, and a white rectangle with a textcursor would appear.

Does anyone know what type of commands (and in what language) this box expected?

I googled around and found no mention of this textbox. Until this day I have not the slightest idea what that thing was.

  • That does ring a bell but vaguely... I believe that dropped you into the NVRAM firmware allowing you to set boot arguments and other things stored in nvram/pram – Steve Chambers Jun 9 '17 at 18:07

Yes, that was MacsBug! (IIRC it was a System Extension that had to be installed/enabled -- although it's been quite a number of years...)

I found a command reference for it here: MacsBug Reference.

There's some more info over on Wikipedia.

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  • Small correction: It was not an (optional) extension. I can safely say that my dad would never install any debug extensions. – Mathew Jun 12 '17 at 6:47
  • You can see in the reference manual, and on wikipedia that it was indeed optional. – Matt Sephton Aug 3 '18 at 13:20
  • MacsBug was the big, fancy assembly-language debugger. Without it installed, you got the ROM debugger instead, which had far more limited capabilities. – Mark Mar 12 at 22:26

That was the Debugger window that was built into the Mac's ROM. I never learned what language worked in it.

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