<s>
Document	B-Language
Structuring	I-Language
Conventions	I-Language
,	O
or	O
DSC	O
,	O
is	O
a	O
set	O
of	O
standards	O
for	O
PostScript	B-Language
,	O
based	O
on	O
the	O
use	O
of	O
comments	O
,	O
which	O
primarily	O
specifies	O
a	O
way	O
to	O
structure	O
a	O
PostScript	B-Language
file	O
and	O
a	O
way	O
to	O
expose	O
that	O
structure	O
in	O
a	O
machine-readable	O
way	O
.	O
</s>
<s>
A	O
PostScript	B-Language
file	O
that	O
conforms	O
to	O
DSC	O
is	O
called	O
a	O
conforming	O
document	O
.	O
</s>
<s>
The	O
need	O
for	O
a	O
structuring	O
convention	O
arises	O
since	O
PostScript	B-Language
is	O
a	O
Turing-complete	B-Algorithm
programming	O
language	O
.	O
</s>
<s>
The	O
addition	O
of	O
structure	O
,	O
with	O
DSC	O
comments	O
exposing	O
that	O
structure	O
,	O
helps	O
provide	O
a	O
way	O
for	O
,	O
e.g.	O
,	O
an	O
intelligent	O
print	B-Device
spooler	I-Device
to	O
have	O
the	O
ability	O
to	O
rearrange	O
the	O
pages	O
for	O
printing	O
,	O
or	O
for	O
a	O
page	O
layout	O
program	O
to	O
find	O
the	O
bounding	B-Algorithm
box	I-Algorithm
of	O
a	O
PostScript	B-Language
file	O
used	O
as	O
a	O
graphic	O
image	O
.	O
</s>
<s>
Collectively	O
,	O
any	O
such	O
program	O
that	O
takes	O
PostScript	B-Language
files	O
as	O
input	O
data	O
is	O
called	O
a	O
document	O
manager	O
.	O
</s>
<s>
In	O
order	O
for	O
a	O
PostScript	B-Language
print	O
file	O
to	O
properly	O
distill	O
to	O
PDF	B-Application
using	O
Adobe	O
tools	O
,	O
it	O
should	O
conform	O
to	O
basic	O
DSC	O
standards	O
.	O
</s>
<s>
Some	O
DSC	O
comments	O
serve	O
a	O
second	O
function	O
,	O
specifying	O
a	O
way	O
to	O
tell	O
the	O
document	O
manager	O
to	O
do	O
certain	O
things	O
,	O
like	O
inserting	O
a	O
font	O
or	O
other	O
PostScript	B-Language
code	O
(	O
collectively	O
called	O
resources	O
)	O
into	O
the	O
file	O
.	O
</s>
<s>
DSC	O
comments	O
that	O
serve	O
this	O
second	O
function	O
are	O
more	O
akin	O
to	O
preprocessing	B-General_Concept
directives	O
and	O
are	O
not	O
purely	O
comments	O
.	O
</s>
<s>
DSC	O
is	O
the	O
basis	O
for	O
encapsulated	B-Language
PostScript	I-Language
;	O
EPS	B-Language
files	I-Language
are	O
conforming	O
documents	O
with	O
further	O
restrictions	O
.	O
</s>
<s>
The	O
set	O
of	O
DSC	O
comments	O
can	O
be	O
expanded	O
by	O
a	O
mechanism	O
called	O
the	O
Open	O
Structuring	O
Conventions	O
,	O
which	O
,	O
together	O
with	O
the	O
EPS	B-Language
specification	O
,	O
form	O
the	O
basis	O
of	O
early	O
versions	O
of	O
the	O
Adobe	O
Illustrator	O
Artwork	O
file	O
format	O
.	O
</s>
<s>
The	O
basic	O
premise	O
of	O
DSC	O
is	O
the	O
separation	O
of	O
prolog	O
(	O
static	O
definitions	O
)	O
and	O
script	O
(	O
code	O
that	O
affects	O
job-specific	O
printed	O
output	O
)	O
,	O
plus	O
the	O
disallowing	O
of	O
certain	O
PostScript	B-Language
operators	O
deemed	O
inappropriate	O
for	O
page	O
descriptions	O
.	O
</s>
<s>
This	O
ensures	O
a	O
basic	O
level	O
of	O
predictability	O
in	O
the	O
PostScript	B-Language
code	O
,	O
thus	O
forming	O
the	O
basis	O
of	O
document	O
manageability	O
.	O
</s>
<s>
(	O
“	O
Zero	O
pages	O
”	O
in	O
DSC	O
usually	O
means	O
“	O
one	O
page	O
without	O
the	O
use	O
of	O
the	O
PostScript	B-Language
‘	O
showpage’	O
operator	O
.	O
)	O
</s>
<s>
The	O
functional	O
independence	O
between	O
pages	O
,	O
plus	O
the	O
disallowing	O
of	O
more	O
PostScript	B-Language
operators	O
in	O
the	O
pages	O
section	O
,	O
form	O
the	O
basis	O
for	O
page	O
independence	O
,	O
which	O
allows	O
pages	O
to	O
be	O
reordered	O
,	O
and	O
independently	O
and	O
randomly	O
accessed	O
.	O
</s>
<s>
This	O
imposed	O
structure	O
is	O
then	O
exposed	O
by	O
delimiting	O
the	O
PostScript	B-Language
file	O
with	O
DSC	O
comments	O
,	O
which	O
normally	O
begin	O
with	O
two	O
percent	O
signs	O
followed	O
by	O
a	O
keyword	O
.	O
</s>
<s>
Finally	O
,	O
the	O
document	O
is	O
marked	O
as	O
conforming	O
by	O
starting	O
it	O
with	O
a	O
comment	O
starting	O
with	O
“	O
%	O
!	O
PS-Adobe-	O
”	O
followed	O
by	O
the	O
DSC	O
version	O
number	O
.	O
</s>
<s>
Sections	O
of	O
reusable	O
PostScript	B-Language
code	O
can	O
be	O
modularized	O
into	O
procsets	O
(	O
procedure	O
sets	O
,	O
corresponding	O
to	O
function	B-Library
libraries	I-Library
in	O
other	O
programming	O
languages	O
)	O
,	O
in	O
order	O
to	O
ease	O
the	O
generation	O
of	O
PostScript	B-Language
code	O
.	O
</s>
<s>
Procsets	O
and	O
other	O
PostScript	B-Language
resources	O
(	O
for	O
example	O
,	O
fonts	O
)	O
can	O
be	O
omitted	O
from	O
the	O
PostScript	B-Language
file	O
itself	O
,	O
and	O
externally	O
referenced	O
by	O
a	O
directive-like	O
DSC	O
comment	O
;	O
such	O
external	O
referencing	O
,	O
however	O
,	O
can	O
only	O
work	O
with	O
a	O
document	O
manager	O
that	O
understands	O
such	O
DSC	O
comments	O
.	O
</s>
<s>
to	O
be	O
good	O
PostScript	B-Language
language	I-Language
programming	O
style.	O
"	O
</s>
<s>
Thus	O
,	O
most	O
PostScript-producing	O
programs	O
output	O
DSC-conformant	O
comments	O
along	O
with	O
the	O
code	O
,	O
although	O
some	O
such	O
programs	O
do	O
not	O
actually	O
produce	O
conforming	O
documents	O
.	O
</s>
<s>
A	O
DSC-conforming	O
document	O
(	O
this	O
one	O
generated	O
by	O
dvips	B-Language
)	O
might	O
begin	O
:	O
</s>
