<s>
In	O
computing	O
,	O
an	O
organizational	B-Protocol
unit	I-Protocol
(	O
OU	O
)	O
provides	O
a	O
way	O
of	O
classifying	O
objects	O
located	O
in	O
directories	O
,	O
or	O
names	O
in	O
a	O
digital	O
certificate	O
hierarchy	O
,	O
typically	O
used	O
either	O
to	O
differentiate	O
between	O
objects	O
with	O
the	O
same	O
name	O
(	O
John	O
Doe	O
in	O
OU	O
"	O
marketing	O
"	O
versus	O
John	O
Doe	O
in	O
OU	O
"	O
customer	O
service	O
"	O
)	O
,	O
or	O
to	O
parcel	O
out	O
authority	O
to	O
create	O
and	O
manage	O
objects	O
(	O
for	O
example	O
:	O
to	O
give	O
rights	O
for	O
user-creation	O
to	O
local	O
technicians	O
instead	O
of	O
having	O
to	O
manage	O
all	O
accounts	O
from	O
a	O
single	O
central	O
group	O
)	O
.	O
</s>
<s>
Organizational	B-Protocol
units	I-Protocol
most	O
commonly	O
appear	O
in	O
X.500	B-Protocol
directories	I-Protocol
,	O
X.509	O
certificates	O
,	O
Lightweight	B-Protocol
Directory	I-Protocol
Access	I-Protocol
Protocol	I-Protocol
(	O
LDAP	B-Protocol
)	O
directories	O
,	O
Active	B-Protocol
Directory	I-Protocol
(	O
AD	O
)	O
,	O
and	O
Lotus	B-Operating_System
Notes	I-Operating_System
directories	O
and	O
certificate	O
trees	O
,	O
but	O
they	O
may	O
feature	O
in	O
almost	O
any	O
modern	O
directory	O
or	O
digital	O
certificate	O
container	B-Language
grouping	O
system	O
.	O
</s>
<s>
In	O
most	O
systems	O
,	O
organizational	B-Protocol
units	I-Protocol
appear	O
within	O
a	O
top-level	O
organization	O
grouping	O
or	O
organization	O
certificate	O
,	O
called	O
a	O
domain	O
.	O
</s>
<s>
When	O
OUs	O
are	O
nested	O
,	O
as	O
one	O
OU	O
contains	O
another	O
OU	O
,	O
this	O
creates	O
a	O
relationship	O
where	O
the	O
contained	O
OU	O
is	O
called	O
the	O
child	O
and	O
the	O
container	B-Language
is	O
called	O
the	O
parent	O
.	O
</s>
<s>
The	O
name	O
organizational	B-Protocol
unit	I-Protocol
appears	O
to	O
represent	O
a	O
single	O
organization	O
with	O
multiple	O
units	O
(	O
departments	O
)	O
within	O
that	O
organization	O
.	O
</s>
<s>
In	O
Sun	B-Application
Java	I-Application
System	I-Application
Directory	I-Application
Server	I-Application
and	O
Microsoft	B-Protocol
Active	I-Protocol
Directory	I-Protocol
(	O
AD	O
)	O
,	O
an	O
organizational	B-Protocol
unit	I-Protocol
(	O
OU	O
)	O
can	O
contain	O
any	O
other	O
unit	O
,	O
including	O
other	O
OUs	O
,	O
users	O
,	O
groups	O
,	O
and	O
computers	O
.	O
</s>
<s>
Organizational	B-Protocol
units	I-Protocol
in	O
separate	O
domains	O
may	O
have	O
identical	O
names	O
but	O
are	O
independent	O
of	O
each	O
other	O
.	O
</s>
<s>
Organizational	B-Protocol
Units	I-Protocol
give	O
a	O
hierarchical	O
structure	O
,	O
and	O
when	O
properly	O
designed	O
can	O
ease	O
administration	O
.	O
</s>
<s>
They	O
adopted	O
the	O
X.500	B-Protocol
OU	O
concept	O
into	O
their	O
next-generation	O
software	O
around	O
1993	O
–	O
Novell	O
with	O
the	O
release	O
of	O
Novell	B-Application
Directory	I-Application
Services	I-Application
(	O
subsequently	O
known	O
as	O
eDirectory	B-Application
)	O
,	O
and	O
Lotus	O
with	O
the	O
release	O
of	O
the	O
third	O
version	O
of	O
Lotus	B-Operating_System
Notes	I-Operating_System
.	O
</s>
<s>
Microsoft	O
allegedly	O
used	O
Novell	O
's	O
directory	O
as	O
a	O
blueprint	O
for	O
the	O
first	O
released	O
versions	O
of	O
AD	O
,	O
but	O
this	O
claim	O
appears	O
suspect	O
,	O
given	O
that	O
X.500	B-Protocol
served	O
as	O
the	O
"	O
granddaddy	O
"	O
of	O
all	O
directory	O
systems	O
.	O
</s>
