In multi-user operating systems, files may be accessed by multiple users.
Permission rights associated with folders (directories) and files are used to
protect or restrict access to files. In UNIX these rights are known as
Read,
Write and
Execute. In Windows NT and Windows 2000 (using the NTFS file-system only as
permissions are not supported with FAT), additional file permissions are
available. In UNIX, three groups of permissions apply to every file. The first
group of permissions defines those of the owner of the file, and are a
combination of the read, write and execute permissions. The second group of
permissions defines those permissions for a group of users. The third group of
permissions defines the permissions for everyone else except the owner and group
members.