Bob Barton taught the guys who wrote Burroughs Fortran to write a compiler in one day. Check out the following story. (Lengthy, sorry. But worth it. Also, I edited it a bit.)

Phillips programmers still had a soft spot in their hearts for the Burroughs 205. So when it came time for them to buy another machine they said that they would buy a Burroughs 205 computer if the following conditions were met:

A. It had to have a compiler that would compile and execute existing IBM 650 Fortransit programs with no modifications whatsoever.

B. The compiler had to compile faster than IBM's Fortransit.

C. The time for loading the compiler and object programs had to be faster than IBM's.

D. The object programs had to run faster.

A call was placed to Bob Barton... Bob said that he could not spend any more effort on the 205. All of his budget was allocated for 220 projects. However, if John Hale would designate three people for the project, he would fly to Dallas for one day and teach them how to write a compiler.

When I heard that someone was flying in from Pasadena to show us how to write a compiler, I was very skeptical. I had seen many other so-called experts from Pasadena and I was invariably disappointed.

The day that Bob spent in Dallas was one of the most amazing days of my life. I am sure that I never learned so much in an eight hour period. We stopped briefly for coffee in the morning and went out for a quick lunch. We did not take a break in the afternoon. The day was intense to say the least. I took a cab to the airport to catch his plane. He talked all the way to the airport and was still shouting information to me as he walked up the steps to the plane and disappeared into it. He said that IBM had spent 25 man-years on Fortransit, but that the three of us could do the job in six months.

They ended up being two guys (not three) and doing it in nine months (not six). Of course, compilers were simpler back then. But they were also far less well understood. These guys hit every one of those crazy requirements and invented virtual memory in the process.

Edit: here is the part about virtual memory. They had to do it to meet requirement D.

The goal of executing object programs faster than the IBM 650 sounded like real trouble to Bob. Both systems had a drum memory. The drum on the 650 rotated at 12500 rpm compared to 3570 rpm on the 205. However, the 205 drum was more sophisticated. It was divided into two areas. The primary storage was 80 words of 0.85 millisecond average access memory. The secondary storage was 4000 words of 8.5 millisecond average access memory.

Bob said that it seemed to him that our only chance of meeting the object speed goal was to figure out an "automatic blocking algorithm". I did not hear the term "virtual memory" until several years later. By an automatic blocking algorithm, he meant moving segments of code from the secondary storage into the primary storage and executing it from there. Since the first goal was to compile existing programs without modification, I would have to do it without the programmer adding any flow directing statements to the programs.

Bob said that a lot of people in Pasadena had tried without success to implement automatic blocking, but I should not let that stop me from trying. I would be the first person to try it with a high-level language. The success of the project seemed to hinge on that algorithm.

During the course of the next two months I did discover the algorithm. The next time that I saw Bob was in the Pasadena Plant in April, 1960. He was in the process of cleaning out his desk... I described the algorithm to him and he became tremendously enthused. Frankly, I had not grasped the importance of the accomplishment.

http://news.ycombinator.com/item?id=2856567. The whole memoir is wonderful. I laughed, I cried. Ok, I didn't cry. But it's all kinds of inspiring awesome.