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+@c
+@c  COPYRIGHT (c) 1988-2002.
+@c  On-Line Applications Research Corporation (OAR).
+@c  All rights reserved.
+@c
+@c  $Id$
+@c
+
+@ifinfo
+@node Preface, , Top, Top
+@end ifinfo
+@unnumbered Preface
+
+This document describes the implementation of the RTEMS filesystem
+infrastructure.  This infrastructure supports the following
+capabilities:
+
+@itemize @bullet
+
+@item Mountable file systems
+
+@item Hierarchical file system directory structure
+
+@item POSIX compliant set of routines for the manipulation of files and directories
+
+@item Individual file and directory support for the following:
+
+@enumerate
+
+@item Permissions for read, write and execute
+
+@item User ID
+
+@item Group ID
+
+@item Access time
+
+@item Modification time
+
+@item Creation time
+
+@end enumerate
+
+@item Hard links to files and directories
+
+@item Symbolic links to files and directories
+
+@end itemize
+
+This has been implemented to provide the framework for a UNIX-like
+file system support. POSIX file and directory functions have been
+implemented that allow a standard method of accessing file, device and
+directory information within file systems. The file system concept that
+has been implemented allows for expansion and adaptation of the file
+system to a variety of existing and future data storage devices. To this
+end, file system mount and unmount capabilities have been included in this
+RTEMS framework.
+
+This framework slightly alters the manner in which devices are handled
+under RTEMS from that of public release 4.0.0 and earlier.  Devices that
+are defined under a given RTEMS configuration will now be registered as
+files in a mounted file system.  Access to these device drivers and their
+associated devices may now be performed through the traditional file system
+open(), read(), write(), lseek(), fstat() and ioctl() functions in addition
+to the interface provided by the IO Manager in the RTEMS Classic API.
+
+An In-Memory File System (IMFS) is included which provides full POSIX
+filesystem functionality yet is RAM based.  The IMFS maintains a
+node structure for each file, device, and directory in each mounted
+instantiation of its file system. The node structure is used to
+manage ownership, access rights, access time, modification time,
+and creation time.  A union of structures within the IMFS nodal
+structure provide for manipulation of file data, device selection,
+or directory content as required by the nodal type. Manipulation of
+these properties is accomplished through the POSIX set of file and
+directory functions.  In addition to being useful in its own right,
+the IMFS serves as a full featured example filesystem.
+
+The intended audience for this document is those persons implementing
+their own filesystem.  Users of the filesystem may find information
+on the implementation useful.  But the user interface to the filesystem
+is through the ISO/ANSI C Library and POSIX 1003.1b file and directory
+APIs.