This is debatable, but markup language is not considered to be a programming language simply because the term is not well-defined. A markup language is used to control the presentation of the data, like representing structured data.

Why markup language is not a programming language?

HTML is used for structural purposes on a web page, not functional ones. Programming languages have functional purposes. HTML, as a markup language doesn't really “do” anything in the sense that a programming language does. ... This is because HTML is not a programming language.

What is markup programming language?

In computer text processing, a markup language is a system for annotating a document in a way that is visually distinguishable from the content. It is used only to format the text, so that when the document is processed for display, the markup language does not appear.