A structured file is a data file segmented into two or more discrete sections in order to denote that the data contained in the file should be treated as related as a whole but containing distinct parts. (An example of a structured file is a database record, which consists of several fields combined into a single file.) Using a structured file, a computer user can store text, sound, and video as segments of the same file.

The segmentation scheme used for a structured file system is determined by the user of the system, and can be any scheme that both suits his convenience and his computer's capability. Allowing users to define their file structures increases the power and flexibility of computers because it allows users to tailor their computing to exactly match their needs.

A structured file system is essential to any useable system of hypertext or hypermedia because including discrete sections within a file is the most convenient way to encode meta-data such as unique identifiers, system instructions, and links.

Contemporary explicit hyper-applications of structured files include hyperbase systems (which divides files into fields) and the Standard General Mark-up Language (which divides files into segments based on data type).

Ted Nelson proposed his Evolutionary List File (ELF) in 1965. The ELF was a structured file system comprised of three classes of elements: entries, lists, and links. Nelson defined an entry as "a discrete unit of information designated by the user"; a list as "an ordered set of entries designated by the user"; and a link as "a connector, designated by the user, between two particular entries." Nelson also defined the file system as including the operations to be performed on the file elements (e.g., adding new entries).

The most notable feature of Nelson's proposal was its adaptability. Nelson outlined a data structure of "zippered lists," but added that these lists "generate only one of various possible [ELFs]." The ELF required data to be in the form of lists, but users could adapt the structure of the lists to fit their needs.

Also, Nelson's proposal foreshadowed two current examples of structured file systems. His notion of combining user-defined fields and operations into one file is incorporated into the popular C++ programming language, and his multiple-linked lists system (shown in his Figure 4) is now known as a relational database.

In 1983, Douglas Engelbart summarized his 20 years of work on the collaborative aspects of the Augment system. The Augment file system expedited collaborative work by using a user-defined structured file scheme to segment data and incorporate meta-data.

In the Augment system, files were divided into hierarchically organized nodes, which could contain text, graphics, or any other digital data. Each node had a unique identifier, on top of which any text (even down to an individual character) could be tagged with an address, capable of indicating who had entered that text and when. Unlimited versioning was available. Linking between two pieces of text within a document or between separate documents was supported. Users could construct a "table of contents" consisting of links to various documents.