Articles or book(s) about the functions behind a scientific calculator

[Dan]

Nice. I'm also looking for info on algorithms for solving equations. I think HP journal from late 70's, early 80's had some articles about that. Also looking to write an editor for entering equations for the solver and for graph sketching, e.g. typing x^2 + 1 results in ENTER 2 ^ 1 + . I recall seeing flowcharts from expired HP patents, but not sure if it was for an editor or something else.