[chubbard]

When he says "He wrote FAT on an airplane" he means with pencil and paper since FAT is so old that there were no laptops to do that on. Which maybe he figured out all of the specs, but he didn't put code down and debug it. Of course in those days writing it on paper was quite common before people typed it into the computer. And that is quite impressive in and of itself. Most of the time people treated that activity as if they were coding so they were very precise. Now a days we're fast, but we aren't as precise.

[marssaxman]

You can write code on paper and debug it in your head, running a simulator of the target environment in your brain. There is no "as if"; this was actually coding.

Coding is something you do in your brain, not in an editor.