TEXDR.AFT is the document Knuth wrote in May 1977 for TEX[1], before a single line of code was written. This was the first thing he typed up into a computer, af

TEXDR.AFT is the document Knuth wrote in May 1977 for TEX[1], before a single line of code was written. This was the first thing he typed up into a computer, after about two months of thinking about the problem. About a month later it was refined to TEX.ONE (both since republished in Digital Typography, along with some of Knuth's diary entries from the time). This is the specification that his two students, Plass and Liang, tried to implement from, while he was in China. Then he came back and decided to implement it himself, which he did over the next year; the SAIL program now known as TeX78. His Pascal (WEB) rewrite was started in 1980 and finished in 1982. So the person you're replying to is correct that TeX had its sophisticated features (as in those present in TEXDR.AFT) in its design, right from the start. Of course the current TeX82 is indeed a rewrite with thousands of changes, but much of the core features of TeX were present in the initial design. Of course one could explain this "counterexample" with the observation that Knuth is not exactly a typical programmer, as he prefers to code on paper (https://news.ycombinator.com/item?id=10172924 https://news.ycombinator.com/item?id=10172924) and spent two months writing a detailed spec, and at least one month getting feedback, before any code was written. Perhaps his initial (hand-written) design was indeed simpler. [1]: Aside: TEX was his original name for it, before the name conflict with Honeywell's TEX https://en.wikipedia.org/wiki/Text_Executive_Programming_Language https://en.wikipedia.org/wiki/Text_Executive_Programming_Lan... forced/inspired him to come up with the Greek letters idea and rename to Tau-Epsilon-Chi properly typeset with the E going below the baseline, in turn represented in ASCII as TeX.)