<s>
The	O
printing	O
subsystem	O
of	O
UNIX	B-Operating_System
System	I-Operating_System
V	I-Operating_System
is	O
one	O
of	O
several	O
standardized	O
systems	O
for	O
printing	O
on	O
Unix	O
,	O
and	O
is	O
typical	O
of	O
commercial	O
System	O
V-based	O
Unix	O
versions	O
such	O
as	O
Solaris	B-Application
and	O
SCO	B-Operating_System
OpenServer	I-Operating_System
.	O
</s>
<s>
A	O
system	O
running	O
this	O
print	O
architecture	O
could	O
traditionally	O
be	O
identified	O
by	O
the	O
use	O
of	O
the	O
user	O
command	O
as	O
the	O
primary	O
interface	O
to	O
the	O
print	O
system	O
,	O
as	O
opposed	O
to	O
the	O
BSD	B-Operating_System
command	O
(	O
though	O
some	O
systems	O
provide	O
as	O
an	O
alias	O
to	O
)	O
.	O
</s>
<s>
Typical	O
user	O
commands	O
available	O
to	O
the	O
System	B-Operating_System
V	I-Operating_System
printing	O
system	O
are	O
:	O
</s>
<s>
In	O
the	O
Unix	O
programming	O
model	O
,	O
device	B-Application
files	I-Application
are	O
special	B-Application
files	I-Application
that	O
act	O
as	O
access	O
points	O
to	O
peripheral	O
devices	O
such	O
as	O
printers	O
.	O
</s>
<s>
While	O
this	O
worked	O
well	O
enough	O
for	O
the	O
case	O
where	O
there	O
was	O
one	O
printer	O
per	O
user	O
,	O
this	O
model	O
did	O
not	O
scale	O
out	O
well	O
to	O
multiple	B-General_Concept
users	I-General_Concept
having	O
to	O
share	O
one	O
printer	O
.	O
</s>
<s>
The	O
solution	O
was	O
to	O
create	O
a	O
queue	O
(	O
or	O
"	O
spool	O
"	O
)	O
of	O
documents	O
to	O
be	O
printed	O
and	O
use	O
a	O
daemon	B-Operating_System
(	O
system	O
process	O
)	O
to	O
manage	O
this	O
queue	O
and	O
send	O
the	O
documents	O
to	O
the	O
printer	O
in	O
the	O
order	O
in	O
which	O
they	O
arrived	O
.	O
</s>
<s>
Such	O
a	O
system	O
,	O
with	O
an	O
command	O
to	O
send	O
documents	O
to	O
the	O
queue	O
,	O
was	O
first	O
introduced	O
in	O
1973	O
in	O
Version	B-Operating_System
4	I-Operating_System
of	O
Unix	O
.	O
</s>
<s>
By	O
the	O
release	O
of	O
System	B-Operating_System
V	I-Operating_System
Release	O
4	O
,	O
the	O
suite	O
of	O
utilities	O
had	O
grown	O
to	O
include	O
commands	O
for	O
canceling	O
print	O
jobs	O
,	O
moving	O
jobs	O
among	O
queues	O
,	O
enabling	O
and	O
disabling	O
queues	O
,	O
enabling	O
and	O
disabling	O
a	O
job	O
scheduler	O
daemon	B-Operating_System
,	O
and	O
status	O
reports	O
of	O
the	O
print	O
system	O
.	O
</s>
<s>
With	O
its	O
distribution	O
in	O
the	O
influential	O
AT&T	B-Operating_System
Unix	I-Operating_System
System	B-Operating_System
V	I-Operating_System
,	O
the	O
interface	O
if	O
not	O
the	O
implementation	O
became	O
the	O
standard	O
for	O
users	O
 '	O
control	O
over	O
printers	O
.	O
</s>
<s>
(	O
In	O
SVR4	O
derivates	O
like	O
SCO	B-Operating_System
UNIX	I-Operating_System
,	O
the	O
command	O
was	O
simply	O
an	O
alias	O
for	O
the	O
command	O
used	O
by	O
the	O
BSD-based	O
system	O
.	O
)	O
</s>
<s>
As	O
late	O
as	O
1996	O
,	O
Running	O
Linux	B-Application
stated	O
"	O
The	O
Linux	B-Application
printing	O
software	O
consists	O
of	O
the	O
UNIX	O
standard	O
lp	B-Device
and	O
lpr	O
software	O
,	O
"	O
but	O
by	O
1999	O
support	O
for	O
lp	B-Device
was	O
waning	O
and	O
the	O
third	O
edition	O
simply	O
stated	O
"	O
The	O
lpr	O
command	O
prints	O
a	O
document	O
on	O
Linux.	O
"	O
</s>
<s>
By	O
2003	O
,	O
a	O
survey	O
of	O
the	O
Debian	O
,	O
Mandrake	O
,	O
Red	O
Hat	O
,	O
Slackware	B-Application
and	O
SuSE	O
distributions	O
showed	O
that	O
all	O
of	O
them	O
were	O
running	O
some	O
combination	O
of	O
lpr	O
,	O
LPRng	O
and	O
CUPS	O
.	O
</s>
<s>
The	O
original	O
System	B-Operating_System
V	I-Operating_System
printing	O
system	O
remains	O
proprietary	O
;	O
however	O
,	O
the	O
Solaris	B-Application
print	O
system	O
,	O
heavily	O
modified	O
from	O
the	O
original	O
,	O
has	O
been	O
released	O
as	O
open	B-Application
source	I-Application
software	I-Application
as	O
part	O
of	O
the	O
OpenSolaris	B-Operating_System
project	O
.	O
</s>
<s>
The	O
Common	B-Application
Unix	I-Application
Printing	I-Application
System	I-Application
emulates	O
both	O
System	B-Operating_System
V	I-Operating_System
and	O
Berkeley	O
print	O
architectures	O
on	O
the	O
interface	O
level	O
,	O
though	O
its	O
internal	O
architecture	O
is	O
different	O
from	O
both	O
.	O
</s>
<s>
In	O
his	O
introduction	O
to	O
a	O
simplified	O
configuration	O
system	O
for	O
lp	B-Device
,	O
author	O
Peter	O
Gray	O
of	O
the	O
University	O
of	O
Wollongong	O
described	O
several	O
weaknesses	O
of	O
the	O
version	O
shipping	O
with	O
the	O
then-current	O
Solaris	B-Application
(	O
operating	O
system	O
)	O
version	O
2	O
.	O
</s>
<s>
As	O
opposed	O
to	O
the	O
single	O
daemon	B-Operating_System
used	O
by	O
the	O
simpler	O
BSD	B-Operating_System
lpr	O
system	O
,	O
the	O
lp	B-Device
system	O
used	O
separate	O
daemons	B-Operating_System
,	O
one	O
for	O
scheduling	O
and	O
one	O
for	O
remote	O
communication	O
.	O
</s>
<s>
The	O
lpr	O
system	O
could	O
be	O
controlled	O
with	O
a	O
single	O
configuration	O
file	O
while	O
lp	B-Device
requires	O
a	O
separate	O
program	O
for	O
administration	O
.	O
</s>
<s>
The	O
lp	B-Device
system	O
did	O
support	O
permissions	O
,	O
but	O
the	O
model	O
did	O
not	O
scale	O
to	O
hundreds	O
of	O
users	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
Gray	O
observed	O
that	O
"	O
many	O
administrators	O
choose	O
to	O
simply	O
run	O
the	O
old	O
lpr/lpd	B-Protocol
system	O
on	O
the	O
SVR4	O
boxes.	O
"	O
</s>
