What was MS-DOS? Historical arguments aplenty *spawn

[Exophase]

And early ARM is pretty crazy too. Since early ARM only addresses 26 bits, they decided that it's a good idea to use the high 6 bits for other purposes, and also the low 2 bits since everything is aligned to 4 bytes. Fortunately this is mended in later revisions, but if ARM was used in some popular computers where backward compatibility is important, I can't imagine what the mess it might be.

I think supporting a legacy 26-bit PC + CPSR mode would be much less of a headache than supporting real mode, virtual mode, 286 protected mode (although that one could have surely been dropped a long time ago), and x87.

But the ISA development would have probably gone in a pretty different direction too. Like a standard set of FP instructions much sooner, and probably SIMD too.

 

[Blazkowicz]

CP/M (control program/monitor ?), was an OS initially written (or at least widely implemented) on Z80 8-bit CPUs.

One of the posters up thread was correct regarding the 380Z computers. These were made by Research Machines and were the standard hardware my UK technical college used in the very early 80s.

I don't know much about the origin of DOS, but I'm pretty sure it was an OS, and not just a command line batch processor.

As far as I know CP/M was made of CCP, the command processor, BDOS the "basic disk operating system", and BIOS which had to be customized for each machine.
That seems to match perfectly - for MS-DOS 7.x - with COMMAND.COM, IO.SYS and the content of the EEPROM or flash chip on the motherboard (on classic MS-DOS 6.x and below there's real code in MSDOS.SYS, so I guess the BDOS's task is carried out by both .SYS files)

In 7.x, i.e. in Windows 9x the MSDOS.SYS is just a dummy file with a few paramaters you can change. I had disabled the Windows logo on boot for fun (98SE loaded insanely fast on my PC, and would shut down instantly)
For a more "serious" purpose you can/could turn a Windows PC into a DOS PC that way, too. Add a line that makes the PC boot straight to DOS no matter what.