Borland Turbo C++ (and Pascal as well) had great help documentation. Every function was thoroughly explained and there was a lot of examples. I learned C just by reading Turbo C++ help docs. I miss that time.
nand2tetris is free on https://www.nand2tetris.org/course
The course is also available on Coursera where it also offers free option if you do evaluation yourself ("auditor" mode).