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Indeed you can. The fact that you are asking indicates that you have a substantial amount to learn. In the typical PC, when you power up, the only software available is that which resides in the BIOS (Basic Input/Output System). There's quite a bit there, substantially more than in the original PCs, but it is, indeed, basic. It knows how to deal with keyboard, monitor, and disk I/O. There is no real executive - that's the job of the software that will boot. The boot record of the medium that is booted from will be placed in memory at a particular location and the processor will then be set to execute from a particular address. From there, everything is up to you.
I would suggest that you get your hands on an old MS-DOS diskette, say 3.3, get some ancient books dealing with MS-DOS, and work from there. You could also use C/PM, and old Unix or QNX, DRDOS, or a number of other things. MS-DOS is terrible, non-reentrant, but you would no doubt have more success locating documentation.
If you take this approach and experiment around, I would recommend you remove your current hard drive or move it to another channel where you're less likely to access it and wipe it out. You will no doubt begin operations in real mode and you won't have the protective measures in place until you put them there yourself.
Historically, a lot of early software was totally independent of even MS-DOS. One booted the whole ball of wax and ran it. Even the early MS Flight Simulators didn't use MS-DOS - it didn't have capabilities to address graphical issues in a timely fashion.
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