ripsaw8080 wrote:

Rekrul wrote:

Besides, isn't Win9X basically just a huge DOS program? As such, it seems only right that DOSBox should run it.

Windows 95, along with Windows NT, was one of the first iterations of Windows that stands free of DOS -- it does not run "on top of" DOS the way Windows 3 does, although it does include a version of DOS that can be run separately (restart in DOS mode). As such, it is not in the scope of the official DOSBox project.

I thought selecting "Restart in MS-DOS mode" simply exited Windows and went to the DOS prompt. On most of the systems I've used Win9x on, it doesn't reboot the whole machine and go through POST again and such.

Of course, DOS can be used to load GRUB, which in turn can load Linux, which is something most operating systems can't do. Aren't a lot of DOS programs essentially whole self-contained OSes anyhow?

DOS programs directly instruct hardware, and many require their own drivers (for example Impulse Tracker) so i guess that is true. It is how i look at it as well.
Same with Nintendo NES games, each game is its own operating system.

Going by that logic, Windows 95/98 are DOS applications AND OSes at the same time. They rely on DOS to boot, and are executed as programs from DOS, but once they load they do their own device handling, memory management, etc. Of course, they're more OS-ey than typical DOS applications as they provide their own APIs for running other programs, hence why they are regarded as separate platforms.

No, Win9X does not rely on DOS to boot, it is a separate OS. Win9X *integrates* DOS as another boot option, it does not run on top of (or within) DOS. That is why Microsoft used the expression "Restart in DOS mode", not "Exit to DOS".

Then why does it just dump me to the DOS prompt instead of going through the POST and everything?

What makes you think that booting an operating system requires POSTing the system?

ripsaw8080 wrote:

What makes you think that booting an operating system requires POSTing the system?

Good point. So, in much the same way DOS can load Win9x, Win9x can load DOS?

mr_bigmouth_502 wrote:

So, in much the same way DOS can load Win9x, Win9x can load DOS?

No, DOS cannot "load" Win9x, nor does Win9X "load" DOS, they simply boot the other after they shut down.

Maybe you remember that Windows 95 would show a shut down screen like "it is now safe to turn off your computer" or so. Of course that was on old PCs, before it was possible for software to turn off the power. Well, instead of showing the shutdown screen, it simply boots DOS.

OK, but does the computer really reboot then? How does DOS get loaded? How does Windows get loaded?

I know, this is pointless and sort of irrelevant, but I'm curious, I want to know.

To boot an OS you simply load its boot code into memory address 0:7C00h and start executing it, that's the ages-old PC standard, which is what the BIOS does when you restart the system, but there's nothing stopping software from doing the same thing. The boot code then loads the rest of the OS.

So, DOS runs as the bootloader, and Windows gets loaded into that memory address, then when the user chooses to "reboot to MS DOS mode", DOS is loaded into that memory address. Am I correct? I sort of figured it was something like this.

mr_bigmouth_502 wrote:

So, DOS runs as the bootloader, and Windows gets loaded into that memory address, then when the user chooses to "reboot to MS DOS mode", DOS is loaded into that memory address. Am I correct? I sort of figured it was something like this.

Well, sort of, although you put it in a strange way. DOS and Win9X simply perform the initial process of loading the other's boot code and executing it after they shut down; it is the boot code that does the real work of loading the OS.

It all makes sense now. Thanks. 😀

Also remember that Win9x and DOS had different AUTOEXEC.BAT and CONFIG.SYS files from each other that get renamed according to which one you are booting.