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Since Microsoft have released the source of 2 old versions of MSDOS for free, I downloaded the ZIP, converted the contents of the v20object folder to an ISO, created a new virtual machine with Virtualbox, and tried to boot it with the ISO I created.

This did not work though.

How can I boot a Virtualbox virtual machine with the newly open sourced MSDOS?

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  • It's just source code. You'd have to compile it into binaries first. Then you'd need to create a compatible virtual hard drive and repartition it to a format supported by MS-DOS manually. On that partition you'd have to put compiled binaries. Finally, you'd need a bootloader that could boot the OS. Note that MS-DOS 2.0 was released in 1981, three years before CD was invented - it probably wouldn't support it at all. Another problem is VM compatibility, modern VM hypervisors probably won't be compatible with DOS because they can't virtualize legacy hardware.
    – gronostaj
    Mar 29, 2014 at 13:20
  • @gronostaj I think that binaries are already supplied, although in 16 bit format. Mar 29, 2014 at 13:23
  • Then the rest of my comment applies. You may want to try using FreeDOS installer to set up drive and bootloader, then substitute FreeDOS with MS-DOS files. Also, I believe Bochs should be able to emulate DOS-compatible hardware. Performance will be poor, but it shouldn't matter when running DOS on modern hardware.
    – gronostaj
    Mar 29, 2014 at 13:27
  • There's no such thing as "Open Source MS-DOS". It's not actually an open source copyright licence.
    – JdeBP
    Mar 30, 2014 at 17:44
  • @JdeBP It just seemed like the clearest way to express what I meant at the time, I will try to change it now. Mar 31, 2014 at 19:01

1 Answer 1

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You are supposed to boot the relevant version of MS-DOS (I know, chicken and egg... I'll get to that in a minute) and use

SYS A:

to put the needed boot files in the right spot. That is assuming that the disk is already formatted. Alternatively, could use FORMAT A: /S

That being said, there is often another way to get this to work. (I did a bit of research on this years ago when I considered writing a multi-version SYS program. But I didn't do that, and what I remember now may be quite old...) Often the trick was just getting IO.SYS at the first part of the disk, and MS-DOS.SYS might be required to be the very next file on the disk. The precise details varied over different versions of MS-DOS.

Using floppy disks may be easier than hard drives, since hard drives had MBRs to work with. But I think this old version of MS-DOS doesn't really support hard drives anyway, so definitely plan to be using floppy disks. (Or, since you said you're using VirtualBox, images of floppy disks.)

I suspect that using SETVER, and running MS-DOS 1.0's SYS from a newer version of DOS, might be helpful (if you're adventurous enough to keep trying ideas that may not work).

You may specifically wish to look for information related to the "boot loader" functionality of the operating system.

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