A file is one or more bytes of data, usually stored on a disk. While the application that creates the file determines the format of the file, the file system determines how the file is stored on the disk and what actions can be performed on it. The file system also stores information about the file in file attributes and extended attributes.

Files are accessed through the file system using file handles. File handles are returned by DosOpen when the file is opened and are used for all subsequent accesses to the file. Files can be be opened, read from, written to, closed, copied, moved, deleted, renamed, and locked. Files can be searched for based on a metacharacter template.

Each open file has a file pointer that indicates the current reading or writing location within the file. The file pointer moves automatically with each read or write operation on the file and can be moved manually by the application.