Floating-point arithmetic
Arbitrary-precision arithmetic
Multiplication algorithm
Division algorithm
Schönhage–Strassen algorithm (FFT Multiplication)
PI (π)
Approximations of π
List of formulae involving π

blog.timothymullican.com/calculating-pi-my-attempt-breaking-pi-record

youtu.be/JvEvTcXF-4Q (youtube video)

www.numberworld.org/y-cruncher/
www.numberworld.org/digits/

If you want to read a more advanced academic source related computational techniques, try "The Art of Computer Programming, Volume 2", by Donald E. Knuth, or "Modern Computer Arithmetic" by Richard P. Brent and Paul Zimmermann. They are not for the weak of heart, truthfully they are a little bit over my head.

If you want to read a truly inspirational book, try a biography about Ramanujan "The Man Who Knew Infinity" by Robert Kanigel. It's a great audio book.

As a project for "Pi-Day" March 14, 2021, a simplified version of this program was created for the Raspberry Pi written in Arm-64 assembly language. The repository is available on GitHub here.

There is a YouTube video describing the 2021 Arm-64 Pi-Day project available on YouTube here.