Markup languages: How we taught computers to understand the structure of human writing

Cultures · Published 9 October 2026 · Updated 25 October 2026 Swipe more like this →

In short: Before digital screens, editors used red pens to annotate manuscripts with instructions for typesetters. Today, we use markup languages to achieve the same goal. By embedding symbols directly into text, these systems allow computers to distinguish between a heading, a paragraph, or a citation, transforming raw data into structured information.

The concept of markup evolved from traditional publishing, where skilled typographers—often called markup men—manually annotated manuscripts with printer's instructions. In the digital age, this practice was formalized into three primary categories: presentational, procedural, and descriptive. Presentational markup, common in word processors, hides formatting codes to provide a 'what you see is what you get' experience. Procedural markup, such as TeX or Markdown, embeds instructions that software follows sequentially, often utilizing macros for efficiency. Descriptive, or semantic, markup focuses on the document's structure, labeling parts for what they are rather than how they should appear.

The history of electronic markup is rooted in the work of IBM researcher Charles Goldfarb, who developed the Generalized Markup Language (GML) in 1969. This work eventually led to the Standard Generalized Markup Language (SGML), released as an ISO standard in 1986. SGML served as a powerful but complex metalanguage, allowing users to define their own tags through a document type definition. While its flexibility was revolutionary, its complexity led to the development of XML in the 1990s, which simplified SGML for web-based applications while maintaining its robust validation capabilities.

HTML, the backbone of the modern web, was specified by Tim Berners-Lee in 1990. Initially influenced by SGML, it became the most widely used markup language globally. The evolution of these languages continues to prioritize the separation of content from presentation. By using descriptive tags, authors can ensure their work remains adaptable across different media, whether it is a scientific paper typeset in LaTeX or a web page rendered in a browser. This decoupling ensures that as technology changes, the underlying structure of our information remains intact and machine-readable.

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