I wrote it up as best as I could in the imgur description, but I'll see if I can summarize it here.
Basically, I was without any modern resources for quite some time. I had a 486, QBASIC and EDIT.com to play with; the rest of the DOS exes etc I didn't want to touch out of fear of buggering up my system as I wasn't very computer literate.
My library had two 1970s books on BASIC which I loaned out (Basic BASIC and Advanced BASIC by James S Coan) and with nothing else to do in the hours after school, I decided to try my hand at it. I played around with it for a bit and built a really primitive "DOS Clone", which relied on a simple series of INPUT's, PRINT's, IF / THEN statements and GOTO. I then also began experimenting with the ASCII Character map which was included in the QBASIC help file, and realized that if I used the correct ASCII codes, I was able to form visualizations on the screen, simple GUIs etc. I combined the two and began adding more and more functionality to it until I eventually named it "OSCI" ("Aussie"). That's pretty much all there was to it.
