alt Hacker News"Glenn came to my tool shed computer room in 1975, so we could "adapt" CP/M to the IMSAI hardware. What this means is that I would rewrite the parts of CP/M that manage things like diskette controllers and CRTs.
Well. come on, I'd already done this so many times that the tips of my fingers were wearing thin, so I designed a general interface, which I called the BIOS (BASIC I/O System) that a good programmer could change on the spot for their hardware. This little BIOS arrangement was the secret to the success of CP/M.
With the BIOS in place, a programmer could make CP/M work with their specialized hardware. With all those hobbyists out there, believe me, there was no shortage of specialized hardware. Glenn and I built a BIOS that afternoon and stuck CP/M on an IMSAI. He demo'd it to Ed Faber and the IMSAI engineers, and they loved it."
Writing a BIOS for a new machine in a single afternoon. Those were the days...
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In retrospect, MS-DOS was a rather trivial program. Sometimes I wonder why I and/or many others did not write an equivalent, even just for fun.
> Writing a BIOS for a new machine in a single afternoon. Those were the days...
This was not a BIOS in the sense of the PC ROM-BIOS, it was an OS module containing device drivers - the equivalent in PC-DOS is IBMIO.COM, in MS-DOS it is IO.SYS.
Of course, writing it in an afternoon was still impressive, but it was a lot smaller than even the IBM PC ROM-BIOS; the MVP was essentially just two device drivers, one for the floppy drive, the other for either the screen/keyboard or for the serial port (if you used an attached serial terminal for IO). Probably IMSAI already had code for those drivers and they were just taking that existing code and interfacing it with the CP/M BIOS API