My entry was a compiler for a custom language I had invented, implemented in Apple Pascal. I forget the details of the language, but the thing worked, and produced 6502 assembler as output. The assembler could be transferred to a DOS 3.3 disk and turned into a runnable program with the BIG MAC assembler. The compiler was mostly recursive descent, except for the expression parsing, where I used precedence parsing. Some local dad who had a job as a mainframe programmer had shown me the railroad switching algorithm to parse expressions, and I thought it was incredibly cool, so it got used too even though it wasn't really necessary.
(I saw a chapter on precedence parsing made it into Beautiful Code...about time that technique got some pr.)
Anyway, on the designated Saturday I showed up and set up my Apple II on a table. Only when the judges came by -- who were respresentatives from a local Radio Shack -- did I realize that my demo was a little lacking. Watching a compiler run is not very exiting, and the cumbersome process to move the intermediate output code over to DOS where it could be assembled and run didn't help. The judges were baffled by what I had done -- it wasn't clear they knew what a compiler was -- and my mumbled explanations didn't help. They moved on.
Later I learned that a program that animated some monkeys on a screen had won the competition.
My buddy didn't fare much better. He had implemented some kind of font-rendering system for his Epson MX-80 dot matrix printer. Had hand-designed all sorts of new fonts for it too, kerning, crazy stuff, it was some kind of proto apple II postscripty-thing. Frankly I was mystified by his project but it seemed like an awful amount of work and rather impressive. I felt better that he hadn't won either.
I took away an important life lesson from this experience.
Yeah yeah, the value of the demo... presentation, practice, performance. That thin shiny stuff sometimes blows away deep heavy stuff. No... I learned that staged competitions with subjective judging by small panels suck.