Formatted text has its genesis in the pre-computer use of underscoring to embolden passages in typewritten manuscripts.
Emphasis, for example, could be achieved in ASCII in a number of ways:[1][2] Surrounding by underscores was also used for book titles: Look it up in _The_C_Programming_Language_.
Formatting can be marked by tags distinguished from the body text by special characters, such as angle brackets in HTML.
Many markup languages can also be edited with specialized software designed to automate some functions or present the output as WYSIWYG.
It is generally an end-user format, written from an application such as Microsoft Word or OpenOffice.org Writer, and not editable by the user once done.