A Zettelkasten (German for "slip box", plural Zettelkästen) or card file consists of small items of information stored on paper slips or cards that may be linked to each other through subject headings or other metadata such as numbers and tags. It has often been used as a system of note-taking and personal knowledge management for research, study, and writing.
In the 1980s, the card file began to be used as metaphor in the interface of some hypertextual personal knowledge base software applications such as NoteCards. In the 1990s, such software inspired the invention of wikis.
As used in research, study, and writing, a card file consists of many individual notes with ideas and other short pieces of information that are taken down as they occur or are acquired. The notes may be numbered hierarchically so that new notes may be inserted at the appropriate place, and contain metadata to allow the note-taker to associate notes with each other. For example, notes may contain subject headings or tags that describe key aspects of the note, and they may reference other notes. The numbering, metadata, format and structure of the notes is subject to variation depending on the specific method employed.
The system not only allows a researcher to store and retrieve information related to their research, but has also long been used to enhance creativity.
Index card#History
The paper slip or card has long been used by individual researchers and by organizations to manage information, including the specialized form of the card catalog.
Coming from a commonplace book tradition, Conrad Gessner (1516–1565) invented his own method of organization in which the individual notes could be rearranged at any time. In retrospect, his recommendation of gluing slips onto bound sheets was an innovation in moving from commonplace books to index cards as a form factor for scholarly information management.
The first early modern card cabinet was designed by 17th-century English inventor Thomas Harrison ( 1640s).