I think that the question was rather why it took 25 seconds to the current compiler to compile an Hello world on a contemporary computer... Turbo Pascal would have definitely done that in a second or less on an 8086 CPU...

It was completely written in assembly

hand written and also optimized for throughput right ? maybe pascal syntax was also parsing friendly.. i don't recall

one thing for sure is that it felt near instant if not real time building small projects, to the point that 14yo me was completely unaware of meaning of Compile until years later.

What bear8642 says. I worked with Anders and interviewed the poor man about it！

>maybe pascal syntax was also parsing friendly..

Yep, designed to be single pass, recursive descent friendly

And despite being single pass, you could call functions and procedures before you defined them (later in the code), by using the forward declaration feature of Pascal.

Because of this feature, the language could also support mutually recursive functions, which some other languages might not have been able to (not sure).