In general computer jargon one codes in a programming language. What is that ? At least to me, it is a Turing-complete language, that is to say, one that has at least a conditional jump instruction (and all the usual arithmetica stuff).

Does HTML have that ? No. The fine art of stuffing a text with tags is called to mark up.

So one codes PASCAL, C, AppleScript, and marks up in SGML, HTML and troff.

I had previously included TeX as a markup language: luckily WWWWolf reminded me that TeX is a real macro language, and you can write real programs with it...