Making a computer produce calculations
Having purchased my own computer, one of my first serious projects was to try and write a program that could produce structural calculations. As a building surveying student at Reading University I was probably the only person in my set who had looked forward to the structural engineering classes and as a BCO was quite happy to check the simpler calculations.
Working out the bending moment and shear force from the loads was easy. I was somewhat stumped as to how to calculate deflections for non standard load cases until our tame checking engineer, Chris Weymouth, gave me a crash course in Mohr's theorem. He also explained that if one checked the beam at intervals of span/20 and took the maximum value one could be satisfied that this would be with a few percent of the actual maximum value. This was crucial in the days when there was a finite wait for the calculation to be done. If you're still around, Chris, I owe you a huge debt.
I cannot remember what the first version looked like, but as my Commodore PET only had a 40 character screen line length, it would have been less than sophisticated. A printout from that era does survive though:
The numbers at the ends of the dotted lines are times: that little block of steel lines took 18 seconds to print!