In 1982 I bought a BBC computer - at a 2007 meeting to commemorate its 25th anniversary it was said that the BBC had expected to sell 12,000 of them, but in the end sold well over a million. This explains why I, like many others, had to put my name on a waiting list and wait several months for delivery. Once mine came, I wasted no time in porting my beam program to it.
The BBC computer was a class act with a much more sophisticated version of the BASIC programming language than the PET. My model B cost me £400. Later I added a floppy disk drive which cost another £400, then moved on to a BBC Master. More about the BBC computer (on The Register site)
In 1984 a colleague and I left Building Control to set a small design and build company. I was responsible for the design side and also started doing design work for a number of contractors, with an emphasis on loft conversions, which lots of people avoided because of the need for structural calculations.
As the volume of design work expanded, my beam design program was progressively improved so as to meet the needs of the user base (me!) As with the PET version, I can't remember what the BBC version looked like, but a few calculation sheets survive. Not that much has changed since!
The key thing, of course, is that I was now producing calculation sheets for Building Control approval rather than as an academic exercise, and this shaped the content. I decided to replicate what one would put on a handwritten calculation, so that any BCO seeing one of these sheets for the first time would have no problems understanding it. To this day most people like the simple clear presentation, though the Structural Engineer's Verulam column did once print a dismissive comment about an unnamed program that fits an entire calculation onto one sheet of paper!