DOS looks trivial to me these days. I kick myself for not going into business making a workalike clone back then.
On a related note, I've kept most of my old machines, except (sadly) my H11. They're just piled up in the basement. Last year I wondered what I had on those old drives, and tried to turn on the computers. None of them would boot. One made a popping sound and smoke came out.
My next attempt was to read the hard drives. My 286 drive wouldn't fit anything modern. The oldest drive I could hook up was in the 486 box, and had to try plugging it into many machines before the old IDE drive was recognized. I was anxious to see what was on it.
Like opening old safes, turns out there was nothing much on it. I was surprised at how simple my old programs were, and how small.
It is a tremendously giving exercise. I practically learned programming doing that. Disassembling an entire MSDOS like operating system and then amending it with print spooling, RAM disk, and the ability to run two tasks simultaneously on special RAM bank switching hardware a.o. (But then we realised that the PC with MSDOS would win and went on doing other more specialised things.)
If you're interested in this kind of stuff, be sure to check the author's (Michael Steil) blog: http://www.pagetable.com/ - he has written all kinds of juicy blog posts about low level programming.
On a related note, I've kept most of my old machines, except (sadly) my H11. They're just piled up in the basement. Last year I wondered what I had on those old drives, and tried to turn on the computers. None of them would boot. One made a popping sound and smoke came out.
My next attempt was to read the hard drives. My 286 drive wouldn't fit anything modern. The oldest drive I could hook up was in the 486 box, and had to try plugging it into many machines before the old IDE drive was recognized. I was anxious to see what was on it.
Like opening old safes, turns out there was nothing much on it. I was surprised at how simple my old programs were, and how small.