4.Markdown

markdown

Markdown is a lightweight markup language with plain text formatting syntax. Its design allows it to be converted to many output formats, but the original tool by the same name only supports HTML.[8] Markdown is often used to format readme files, for writing messages in online discussion forums, and to create rich text using a plain text editor.

John Gruber created the Markdown language in 2004 in collaboration with Aaron Swartz on the syntax, with the goal of enabling people “to write using an easy-to-read and easy-to-write plain text format, optionally convert it to structurally valid XHTML (or HTML)”.

Its key design goal is readability – that the language be readable as-is, without looking like it has been marked up with tags or formatting instructions, unlike text formatted with a markup language, such as Rich Text Format (RTF) or HTML, which have obvious tags and formatting instructions. To this end, its main inspiration is the existing conventions for marking up plain text in email, though it also draws from earlier markup languages, notably setext, Textile, and reStructuredText.

kramdown Documentation

kramdown is first and foremost a library for converting text written in a superset of Markdown to HTML. However, due to its modular architecture it is able to support additional input and output formats.

kramdown Quick Reference

kramdown (sic, not Kramdown or KramDown, just kramdown) is a free MIT-licensed Ruby library for parsing and converting a superset of Markdown.