My earliest exposure to computers was at the age of 16, when I took a correspondence course "Programming of Hollerith Machines". They work with punched cards, switchboards and cables to program them. The next step was learning Algol-60 in my second semester as a mathematics student.
While I studied mathematics, I took a courseabout numerical mathematics.The two terms I liked best were ADI for alternating directions implicit (method) and SOR for successive overrelaxation. Both are used to solve partial differential equations.
One rule that we were told to always respect was: If you need to divide more than once by the same value, calcuate the reciprocal of that vallue and mutliply by it. That is, because even today, division is much slower than multiplication.

Programming languages

My first "programming language" was of course switchboards and cables. After that in 1971 Algol-60 and from 1973 Fortran and more modern variants of Fortran. Since then I have learned a substantial number of languages, some of which are listed below in mostly chronological order. My favorite and almost exclusively used language is Python. Languages that I currently actively use are underlined..
Tools like HTML, CSS and Javascript that I use to develop this website I do not usually employ. HTML is generated via Pug/Jade and CSS via Stylus. The framework is Flask. The entire code consists of Python, Pug/Jade, CSS and Javascript. HTMl is created on the fly from Pug templates with PyPugJS. Bootstrap or Foundation and jQuery scripts and Bootstrap or Foundation CSS are also used.