Fascinating video that popped up on my radar today of Stephen Wolfram demoing Mathematica in 1989 I was quite blown away by how powerful and ahead of its time it was, even back then, with features like interactive programming in a very high level, multi-paradigm language for symbolic computation with rich, introspectable outputs and various thoughtful design decisions around interoperability, extensibility and API (as validated by how none of the API functions demo'd have changed AFAIK in 30+ years!)

Mathematica has indeed an excellent track record for API stability. Wolfram had been doing computer algebra in Lisp before, so he was familiar with interactive high-level programming. But bringing this to a much wider market remains a remarkable achievement.

Wolfram had been doing computer algebra in Lisp before, so he was familiar with interactive high-level programming. But bringing this to a much wider market remains a remarkable achievement

Good point and he had also cut his teeth on SMP after that, which apparently Rob Pike convinced him to write in C instead of Lisp and I'm sure that helped with performance and portability