Superuser (aka "root") is the UNIX System Manager
On any system someone must be able to kill any runaway
program, purge corrupted files, reset passwords when
users forget them, remove users' permission to use the
system, and a myriad of other system management tasks.
On MPE this person is called the
System Manager (actually, any user with SM
capability).
On UNIX this special user is known
as superuser or root (not to
be confused with the root directory).
Superuser can override file security and do almost anything she
wants on the system (she cannot see
your password, since it is encrypted, but she can change it).
In fact, any user with a userid of 0 is a superuser.
Naturally, such users should always have a password.
It is
not good practice for the system administrator
to always logon as superuser. It is too easy to make a trivial mistake
and damage the system, perhaps by rm *
in an
important directory. Instead, logon as a regular user, then
switch to superuser with the su command when you need it.
In a Hierarchical File System, one
directory is the root or start of the tree. Other
directories hang off root and they in turn can have
subdirectories. On UNIX and
POSIX, root is specified as a
forward slash "/". On DOS, root is specified as a
backward slash "\".
This meaning of root should not be confused with the alternate
meaning of root as the UNIX system manager (that is,
superuser).