File control blocks (FCB), sometimes referred to as file descriptors, are data
structures that hold information about a file. When an operating system needs to
access a file, it creates an associated file control block to manage the file.
The structure of the file control block differs between operating systems, but
most file control blocks include the following parts:
Filename of Directory name
Location of file on secondary storage
Length of file (usually in bytes)
Date and time or creation or last access
Access Rights (Read only, Hidden, Write, etc)