Folder,
directory[1],
catalog, or
drawer[2], in
computing, is a virtual container within a digital
file system, in which groups of
computer files and other folders can be kept and organized.
A typical file system may contain thousands (or even hundreds of thousands) of folders. Files are kept organized by storing related files in the same folder. A folder contained inside another folder is called a subfolder of that folder. Together, the folders form a hierarchy, or tree structure.
Historically, and even on some modern embedded devices, the file systems either have no support for folders at all or only have a flat directory structure, meaning subfolders are not allowed; there is only a group of top-level folders each containing files. The first popular fully general hierarchical file system was that of Multics. This type of file system was an early research interest of Dennis Ritchie.
In modern times in Unix-like systems, especially Linux, folders structure is defined by the Filesystem Hierarchy Standard.
