<s>
PostScript	B-Language
(	O
PS	B-Language
)	O
is	O
a	O
page	O
description	O
language	O
in	O
the	O
electronic	O
publishing	O
and	O
desktop	O
publishing	O
realm	O
.	O
</s>
<s>
It	O
is	O
a	O
dynamically	O
typed	O
,	O
concatenative	B-Language
programming	I-Language
language	I-Language
.	O
</s>
<s>
The	O
concepts	O
of	O
the	O
PostScript	B-Language
language	I-Language
were	O
seeded	O
in	O
1976	O
by	O
John	O
Gaffney	O
at	O
Evans	O
&	O
Sutherland	O
,	O
a	O
computer	O
graphics	O
company	O
.	O
</s>
<s>
At	O
that	O
time	O
Gaffney	O
and	O
John	O
Warnock	O
were	O
developing	O
an	O
interpreter	B-Application
for	O
a	O
large	O
three-dimensional	O
graphics	O
database	O
of	O
New	O
York	O
Harbor	O
.	O
</s>
<s>
In	O
1975-76	O
Bob	O
Sproull	O
and	O
William	O
Newman	O
developed	O
the	O
Press	O
format	O
,	O
which	O
was	O
eventually	O
used	O
in	O
the	O
Xerox	B-Operating_System
Star	I-Operating_System
system	O
to	O
drive	O
laser	O
printers	O
.	O
</s>
<s>
But	O
Press	O
,	O
a	O
data	O
format	O
rather	O
than	O
a	O
language	O
,	O
lacked	O
flexibility	O
,	O
and	O
PARC	O
mounted	O
the	O
Interpress	B-Language
effort	O
to	O
create	O
a	O
successor	O
.	O
</s>
<s>
This	O
work	O
later	O
evolved	O
and	O
expanded	O
into	O
the	O
Interpress	B-Language
language	O
.	O
</s>
<s>
They	O
,	O
together	O
with	O
Doug	O
Brotz	O
,	O
Ed	O
Taft	O
and	O
Bill	O
Paxton	O
created	O
a	O
simpler	O
language	O
,	O
similar	O
to	O
Interpress	B-Language
,	O
called	O
PostScript	B-Language
,	O
which	O
went	O
on	O
the	O
market	O
in	O
1984	O
.	O
</s>
<s>
At	O
about	O
this	O
time	O
they	O
were	O
visited	O
by	O
Steve	O
Jobs	O
,	O
who	O
urged	O
them	O
to	O
adapt	O
PostScript	B-Language
to	O
be	O
used	O
as	O
the	O
language	O
for	O
driving	O
laser	O
printers	O
.	O
</s>
<s>
In	O
March	O
1985	O
,	O
the	O
Apple	O
LaserWriter	O
was	O
the	O
first	O
printer	O
to	O
ship	O
with	O
PostScript	B-Language
,	O
sparking	O
the	O
desktop	O
publishing	O
(	O
DTP	O
)	O
revolution	O
in	O
the	O
mid-1980s	O
.	O
</s>
<s>
The	O
combination	O
of	O
technical	O
merits	O
and	O
widespread	O
availability	O
made	O
PostScript	B-Language
a	O
language	O
of	O
choice	O
for	O
graphical	O
output	O
for	O
printing	O
applications	O
.	O
</s>
<s>
For	O
a	O
time	O
an	O
interpreter	B-Application
(	O
sometimes	O
referred	O
to	O
as	O
a	O
RIP	O
for	O
Raster	B-Algorithm
Image	I-Algorithm
Processor	O
)	O
for	O
the	O
PostScript	B-Language
language	I-Language
was	O
a	O
common	O
component	O
of	O
laser	O
printers	O
,	O
into	O
the	O
1990s	O
.	O
</s>
<s>
However	O
,	O
the	O
cost	O
of	O
implementation	O
was	O
high	O
;	O
computers	O
output	O
raw	O
PS	B-Language
code	O
that	O
would	O
be	O
interpreted	B-Application
by	O
the	O
printer	O
into	O
a	O
raster	B-Algorithm
image	I-Algorithm
at	O
the	O
printer	O
's	O
natural	O
resolution	B-Algorithm
.	O
</s>
<s>
This	O
required	O
high	O
performance	O
microprocessors	B-Architecture
and	O
ample	O
memory	B-General_Concept
.	O
</s>
<s>
The	O
LaserWriter	O
used	O
a	O
12MHz	O
Motorola	B-Device
68000	I-Device
,	O
making	O
it	O
faster	O
than	O
any	O
of	O
the	O
Macintosh	O
computers	O
to	O
which	O
it	O
attached	O
.	O
</s>
<s>
When	O
the	O
laser	O
printer	O
engines	O
themselves	O
cost	O
over	O
a	O
thousand	O
dollars	O
the	O
added	O
cost	O
of	O
PS	B-Language
was	O
marginal	O
.	O
</s>
<s>
But	O
as	O
printer	O
mechanisms	O
fell	O
in	O
price	O
,	O
the	O
cost	O
of	O
implementing	O
PS	B-Language
became	O
too	O
great	O
a	O
fraction	O
of	O
overall	O
printer	O
cost	O
;	O
in	O
addition	O
,	O
with	O
desktop	O
computers	O
becoming	O
more	O
powerful	O
,	O
it	O
no	O
longer	O
made	O
sense	O
to	O
offload	O
the	O
rasterization	O
work	O
onto	O
the	O
resource-constrained	O
printer	O
.	O
</s>
<s>
By	O
2001	O
,	O
few	O
lower-end	O
printer	O
models	O
came	O
with	O
support	O
for	O
PostScript	B-Language
,	O
largely	O
due	O
to	O
growing	O
competition	O
from	O
much	O
cheaper	O
non-PostScript	O
ink	O
jet	O
printers	O
,	O
and	O
new	O
software-based	O
methods	O
to	O
render	O
PostScript	B-Language
images	O
on	O
the	O
computer	O
,	O
making	O
them	O
suitable	O
for	O
any	O
printer	O
;	O
PDF	B-Application
,	O
a	O
descendant	O
of	O
PostScript	B-Language
,	O
provides	O
one	O
such	O
method	O
,	O
and	O
has	O
largely	O
replaced	O
PostScript	B-Language
as	O
de	O
facto	O
standard	O
for	O
electronic	O
document	O
distribution	O
.	O
</s>
<s>
On	O
high-end	O
printers	O
,	O
PostScript	B-Language
processors	O
remain	O
common	O
,	O
and	O
their	O
use	O
can	O
dramatically	O
reduce	O
the	O
CPU	O
work	O
involved	O
in	O
printing	O
documents	O
,	O
transferring	O
the	O
work	O
of	O
rendering	O
PostScript	B-Language
images	O
from	O
the	O
computer	O
to	O
the	O
printer	O
.	O
</s>
<s>
The	O
first	O
version	O
of	O
the	O
PostScript	B-Language
language	I-Language
was	O
released	O
to	O
the	O
market	O
in	O
1984	O
.	O
</s>
<s>
PostScript	B-Language
Level	O
2	O
was	O
introduced	O
in	O
1991	O
,	O
and	O
included	O
several	O
improvements	O
:	O
improved	O
speed	O
and	O
reliability	O
,	O
support	O
for	O
in-Raster	O
Image	O
Processing	O
(	O
RIP	O
)	O
separations	O
,	O
image	B-General_Concept
decompression	I-General_Concept
(	O
for	O
example	O
,	O
JPEG	O
images	O
could	O
be	O
rendered	O
by	O
a	O
PostScript	B-Language
program	O
)	O
,	O
support	O
for	O
composite	O
fonts	O
,	O
and	O
the	O
form	O
mechanism	O
for	O
caching	O
reusable	O
content	O
.	O
</s>
<s>
PostScript	B-Language
3	O
(	O
Adobe	O
dropped	O
the	O
"	O
level	O
"	O
terminology	O
in	O
favor	O
of	O
simple	O
versioning	O
)	O
came	O
at	O
the	O
end	O
of	O
1997	O
,	O
and	O
along	O
with	O
many	O
new	O
dictionary-based	O
versions	O
of	O
older	O
operators	O
,	O
introduced	O
better	O
color	O
handling	O
and	O
new	O
filters	O
(	O
which	O
allow	O
in-program	O
compression/decompression	O
,	O
program	O
chunking	O
,	O
and	O
advanced	O
error-handling	O
)	O
.	O
</s>
<s>
PostScript	B-Language
3	O
was	O
significant	O
in	O
terms	O
of	O
replacing	O
the	O
existing	O
proprietary	O
color	O
electronic	O
prepress	O
systems	O
,	O
then	O
widely	O
used	O
for	O
magazine	O
production	O
,	O
through	O
the	O
introduction	O
of	O
smooth	O
shading	O
operations	O
with	O
up	O
to	O
4096	O
shades	O
of	O
grey	O
(	O
rather	O
than	O
the	O
256	O
available	O
in	O
PostScript	B-Language
Level	O
2	O
)	O
,	O
as	O
well	O
as	O
DeviceN	O
,	O
a	O
color	B-Algorithm
space	I-Algorithm
that	O
allowed	O
the	O
addition	O
of	O
additional	O
ink	O
colors	O
(	O
called	O
spot	O
colors	O
)	O
into	O
composite	O
color	O
pages	O
.	O
</s>
<s>
Prior	O
to	O
the	O
introduction	O
of	O
Interpress	B-Language
and	O
PostScript	B-Language
,	O
printers	O
were	O
designed	O
to	O
print	O
character	O
output	O
given	O
the	O
texttypically	O
in	O
ASCIIas	O
input	O
.	O
</s>
<s>
There	O
were	O
a	O
number	O
of	O
technologies	O
for	O
this	O
task	O
,	O
but	O
most	O
shared	O
the	O
property	O
that	O
the	O
glyphs	B-Application
were	O
physically	O
difficult	O
to	O
change	O
,	O
as	O
they	O
were	O
stamped	O
onto	O
typewriter	O
keys	O
,	O
bands	O
of	O
metal	O
,	O
or	O
optical	O
plates	O
.	O
</s>
<s>
As	O
they	O
grew	O
in	O
sophistication	O
,	O
dot	O
matrix	O
printers	O
started	O
including	O
several	O
built-in	O
fonts	O
from	O
which	O
the	O
user	O
could	O
select	O
,	O
and	O
some	O
models	O
allowed	O
users	O
to	O
upload	O
their	O
own	O
custom	O
glyphs	B-Application
into	O
the	O
printer	O
.	O
</s>
<s>
Dot	O
matrix	O
printers	O
also	O
introduced	O
the	O
ability	O
to	O
print	O
raster	B-Algorithm
graphics	I-Algorithm
.	O
</s>
<s>
The	O
graphics	O
were	O
interpreted	B-Application
by	O
the	O
computer	O
and	O
sent	O
as	O
a	O
series	O
of	O
dots	O
to	O
the	O
printer	O
using	O
a	O
series	O
of	O
escape	O
sequences	O
.	O
</s>
<s>
These	O
printer	O
control	O
languages	O
varied	O
from	O
printer	O
to	O
printer	O
,	O
requiring	O
program	O
authors	O
to	O
create	O
numerous	O
drivers	B-Application
.	O
</s>
<s>
Vector	O
graphics	O
printing	O
was	O
left	O
to	O
special-purpose	O
devices	O
,	O
called	O
plotters	B-Operating_System
.	O
</s>
<s>
Almost	O
all	O
plotters	B-Operating_System
shared	O
a	O
common	O
command	O
language	O
,	O
HPGL	B-Language
,	O
but	O
were	O
of	O
limited	O
use	O
for	O
anything	O
other	O
than	O
printing	O
graphics	O
.	O
</s>
<s>
Laser	O
printers	O
combine	O
the	O
best	O
features	O
of	O
both	O
printers	O
and	O
plotters	B-Operating_System
.	O
</s>
<s>
Like	O
plotters	B-Operating_System
,	O
laser	O
printers	O
offer	O
high	O
quality	O
line	O
art	O
,	O
and	O
like	O
dot-matrix	O
printers	O
,	O
they	O
are	O
able	O
to	O
generate	O
pages	O
of	O
text	O
and	O
raster	B-Algorithm
graphics	I-Algorithm
.	O
</s>
<s>
Unlike	O
either	O
printers	O
or	O
plotters	B-Operating_System
,	O
a	O
laser	O
printer	O
makes	O
it	O
possible	O
to	O
position	O
high-quality	O
graphics	O
and	O
text	O
on	O
the	O
same	O
page	O
.	O
</s>
<s>
PostScript	B-Language
made	O
it	O
possible	O
to	O
exploit	O
fully	O
these	O
characteristics	O
by	O
offering	O
a	O
single	O
control	O
language	O
that	O
could	O
be	O
used	O
on	O
any	O
brand	O
of	O
printer	O
.	O
</s>
<s>
PostScript	B-Language
went	O
beyond	O
the	O
typical	O
printer	O
control	O
language	O
and	O
was	O
a	O
complete	O
programming	O
language	O
of	O
its	O
own	O
.	O
</s>
<s>
Many	O
applications	O
can	O
transform	O
a	O
document	O
into	O
a	O
PostScript	B-Language
program	O
:	O
the	O
execution	O
of	O
which	O
results	O
in	O
the	O
original	O
document	O
.	O
</s>
<s>
This	O
program	O
can	O
be	O
sent	O
to	O
an	O
interpreter	B-Application
in	O
a	O
printer	O
,	O
which	O
results	O
in	O
a	O
printed	O
document	O
,	O
or	O
to	O
one	O
inside	O
another	O
application	O
,	O
which	O
will	O
display	O
the	O
document	O
on-screen	O
.	O
</s>
<s>
PostScript	B-Language
is	O
noteworthy	O
for	O
implementing	O
'	O
on-the	O
fly	O
 '	O
rasterization	O
in	O
which	O
everything	O
,	O
even	O
text	O
,	O
is	O
specified	O
in	O
terms	O
of	O
straight	O
lines	O
and	O
cubic	O
Bézier	O
curves	O
(	O
previously	O
found	O
only	O
in	O
CAD	B-Application
applications	O
)	O
,	O
which	O
allows	O
arbitrary	O
scaling	O
,	O
rotating	O
and	O
other	O
transformations	O
.	O
</s>
<s>
When	O
the	O
PostScript	B-Language
program	O
is	O
interpreted	B-Application
,	O
the	O
interpreter	B-Application
converts	O
these	O
instructions	O
into	O
the	O
dots	O
needed	O
to	O
form	O
the	O
output	O
.	O
</s>
<s>
For	O
this	O
reason	O
,	O
PostScript	B-Language
interpreters	B-Application
are	O
occasionally	O
called	O
PostScript	B-Language
raster	B-Algorithm
image	I-Algorithm
processors	O
,	O
or	O
RIPs	O
.	O
</s>
<s>
Almost	O
as	O
complex	O
as	O
PostScript	B-Language
itself	O
is	O
its	O
handling	O
of	O
fonts	O
.	O
</s>
<s>
The	O
font	O
system	O
uses	O
the	O
PS	B-Language
graphics	O
primitives	O
to	O
draw	O
glyphs	B-Application
as	O
curves	O
,	O
which	O
can	O
then	O
be	O
rendered	O
at	O
any	O
resolution	B-Algorithm
.	O
</s>
<s>
One	O
issue	O
is	O
that	O
fonts	O
do	O
not	O
scale	O
linearly	O
at	O
small	O
sizes	O
and	O
features	O
of	O
the	O
glyphs	B-Application
will	O
become	O
proportionally	O
too	O
large	O
or	O
small	O
and	O
start	O
to	O
look	O
displeasing	O
.	O
</s>
<s>
PostScript	B-Language
avoided	O
this	O
problem	O
with	O
the	O
inclusion	O
of	O
font	O
hinting	O
,	O
in	O
which	O
additional	O
information	O
is	O
provided	O
in	O
horizontal	O
or	O
vertical	O
bands	O
to	O
help	O
identify	O
the	O
features	O
in	O
each	O
letter	O
that	O
are	O
important	O
for	O
the	O
rasterizer	O
to	O
maintain	O
.	O
</s>
<s>
The	O
result	O
was	O
significantly	O
better-looking	O
fonts	O
even	O
at	O
low	B-Algorithm
resolution	I-Algorithm
.	O
</s>
<s>
At	O
the	O
time	O
,	O
the	O
technology	O
for	O
including	O
these	O
hints	O
in	O
fonts	O
was	O
carefully	O
guarded	O
,	O
and	O
the	O
hinted	O
fonts	O
were	O
compressed	O
and	O
encrypted	O
into	O
what	O
Adobe	O
called	O
a	O
Type	O
1	O
Font	O
(	O
also	O
known	O
as	O
PostScript	B-Language
Type	O
1	O
Font	O
,	O
PS1	O
,	O
T1	O
or	O
Adobe	O
Type	O
1	O
)	O
.	O
</s>
<s>
Type	O
1	O
was	O
effectively	O
a	O
simplification	O
of	O
the	O
PS	B-Language
system	O
to	O
store	O
outline	O
information	O
only	O
,	O
as	O
opposed	O
to	O
being	O
a	O
complete	O
language	O
(	O
PDF	B-Application
is	O
similar	O
in	O
this	O
regard	O
)	O
.	O
</s>
<s>
Those	O
who	O
did	O
not	O
license	O
the	O
technology	O
were	O
left	O
with	O
the	O
Type	O
3	O
Font	O
(	O
also	O
known	O
as	O
PostScript	B-Language
Type	O
3	O
Font	O
,	O
PS3	O
or	O
T3	O
)	O
.	O
</s>
<s>
Type	O
3	O
fonts	O
allowed	O
for	O
all	O
the	O
sophistication	O
of	O
the	O
PostScript	B-Language
language	I-Language
,	O
but	O
without	O
the	O
standardized	O
approach	O
to	O
hinting	O
.	O
</s>
<s>
The	O
CFF/Type2	O
format	O
later	O
became	O
the	O
basis	O
for	O
handling	O
PostScript	B-Language
outlines	O
in	O
OpenType	O
fonts	O
.	O
</s>
<s>
Retail	O
tools	O
such	O
as	O
Altsys	O
Fontographer	B-Operating_System
(	O
acquired	O
by	O
Macromedia	O
in	O
January	O
1995	O
,	O
owned	O
by	O
FontLab	B-Application
since	O
May	O
2005	O
)	O
added	O
the	O
ability	O
to	O
create	O
Type	O
1	O
fonts	O
.	O
</s>
<s>
Since	O
then	O
,	O
many	O
free	O
Type	O
1	O
fonts	O
have	O
been	O
released	O
;	O
for	O
instance	O
,	O
the	O
fonts	O
used	O
with	O
the	O
TeX	B-Application
typesetting	O
system	O
are	O
available	O
in	O
this	O
format	O
.	O
</s>
<s>
In	O
the	O
early	O
1990s	O
there	O
were	O
several	O
other	O
systems	O
for	O
storing	O
outline-based	O
fonts	O
,	O
developed	O
by	O
Bitstream	O
and	O
Metafont	B-Operating_System
for	O
instance	O
,	O
but	O
none	O
included	O
a	O
general-purpose	O
printing	O
solution	O
and	O
they	O
were	O
therefore	O
not	O
widely	O
used	O
.	O
</s>
<s>
When	O
printed	O
to	O
a	O
PostScript	B-Language
output	O
device	O
,	O
the	O
unneeded	O
parts	O
of	O
the	O
OpenType	O
font	O
are	O
omitted	O
,	O
and	O
what	O
is	O
sent	O
to	O
the	O
device	O
by	O
the	O
driver	O
is	O
the	O
same	O
as	O
it	O
would	O
be	O
for	O
a	O
TrueType	O
or	O
Type	O
1	O
font	O
,	O
depending	O
on	O
which	O
kind	O
of	O
outlines	O
were	O
present	O
in	O
the	O
OpenType	O
font	O
.	O
</s>
<s>
In	O
the	O
1980s	O
,	O
Adobe	O
drew	O
most	O
of	O
its	O
revenue	O
from	O
the	O
licensing	O
fees	O
for	O
their	O
implementation	O
of	O
PostScript	B-Language
for	O
printers	O
,	O
known	O
as	O
a	O
raster	B-Algorithm
image	I-Algorithm
processor	O
or	O
RIP	O
.	O
</s>
<s>
As	O
a	O
number	O
of	O
new	O
RISC-based	B-Architecture
platforms	O
became	O
available	O
in	O
the	O
mid-1980s	O
,	O
some	O
found	O
Adobe	O
's	O
support	O
of	O
the	O
new	O
machines	O
to	O
be	O
lacking	O
.	O
</s>
<s>
This	O
and	O
issues	O
of	O
cost	O
led	O
to	O
third-party	O
implementations	O
of	O
PostScript	B-Language
becoming	O
common	O
,	O
particularly	O
in	O
low-cost	O
printers	O
(	O
where	O
the	O
licensing	O
fee	O
was	O
the	O
sticking	O
point	O
)	O
or	O
in	O
high-end	O
typesetting	O
equipment	O
(	O
where	O
the	O
quest	O
for	O
speed	O
demanded	O
support	O
for	O
new	O
platforms	O
faster	O
than	O
Adobe	O
could	O
provide	O
)	O
.	O
</s>
<s>
At	O
one	O
point	O
,	O
Microsoft	O
licensed	O
to	O
Apple	O
a	O
PostScript-compatible	O
interpreter	B-Application
it	O
had	O
bought	O
called	O
TrueImage	B-Language
,	O
and	O
Apple	O
licensed	O
to	O
Microsoft	O
its	O
new	O
font	O
format	O
,	O
TrueType	O
.	O
</s>
<s>
Apple	O
ended	O
up	O
reaching	O
an	O
accord	O
with	O
Adobe	O
and	O
licensed	O
genuine	O
PostScript	B-Language
for	O
its	O
printers	O
,	O
but	O
TrueType	O
became	O
the	O
standard	O
outline	O
font	O
technology	O
for	O
both	O
Windows	O
and	O
the	O
Macintosh	O
.	O
</s>
<s>
Today	O
,	O
third-party	O
PostScript-compatible	O
interpreters	B-Application
are	O
widely	O
used	O
in	O
printers	O
and	O
multifunction	O
peripherals	O
(	O
MFPs	O
)	O
.	O
</s>
<s>
For	O
example	O
,	O
CSR	O
plc	O
's	O
IPS	O
PS3	O
interpreter	B-Application
,	O
formerly	O
known	O
as	O
PhoenixPage	O
,	O
is	O
standard	O
in	O
many	O
printers	O
and	O
MFPs	O
,	O
including	O
those	O
developed	O
by	O
Hewlett-Packard	O
and	O
sold	O
under	O
the	O
LaserJet	O
and	O
Color	O
LaserJet	O
lines	O
.	O
</s>
<s>
Other	O
third-party	O
PostScript	B-Language
solutions	O
used	O
by	O
print	O
and	O
MFP	O
manufacturers	O
include	O
Jaws	O
and	O
the	O
Harlequin	B-Language
RIP	I-Language
,	O
both	O
by	O
Global	O
Graphics	O
.	O
</s>
<s>
A	O
free	B-Application
software	I-Application
version	O
,	O
with	O
several	O
other	O
applications	O
,	O
is	O
Ghostscript	B-Language
.	O
</s>
<s>
Several	O
compatible	O
interpreters	B-Application
are	O
listed	O
on	O
the	O
Undocumented	O
Printing	O
Wiki	O
.	O
</s>
<s>
Some	O
basic	O
,	O
inexpensive	O
laser	O
printers	O
do	O
not	O
support	O
PostScript	B-Language
,	O
instead	O
coming	O
with	O
drivers	B-Application
that	O
simply	O
rasterize	O
the	O
platform	O
's	O
native	O
graphics	O
formats	O
rather	O
than	O
converting	O
them	O
to	O
PostScript	B-Language
first	O
.	O
</s>
<s>
When	O
PostScript	B-Language
support	O
is	O
needed	O
for	O
such	O
a	O
printer	O
,	O
Ghostscript	B-Language
can	O
be	O
used	O
.	O
</s>
<s>
There	O
are	O
also	O
a	O
number	O
of	O
commercial	O
PostScript	B-Language
interpreters	B-Application
,	O
such	O
as	O
TeleType	O
Co.	O
'	O
s	O
T-Script	O
.	O
</s>
<s>
PostScript	B-Language
became	O
commercially	O
successful	O
due	O
to	O
the	O
introduction	O
of	O
the	O
graphical	B-Application
user	I-Application
interface	I-Application
(	O
GUI	B-Application
)	O
,	O
allowing	O
designers	O
to	O
directly	O
lay	O
out	O
pages	O
for	O
eventual	O
output	O
on	O
laser	O
printers	O
.	O
</s>
<s>
However	O
,	O
the	O
GUI	B-Application
's	O
own	O
graphics	O
systems	O
were	O
generally	O
much	O
less	O
sophisticated	O
than	O
PostScript	B-Language
;	O
Apple	O
's	O
QuickDraw	B-Operating_System
,	O
for	O
instance	O
,	O
supported	O
only	O
basic	O
lines	O
and	O
arcs	O
,	O
not	O
the	O
complex	O
B-splines	B-Algorithm
and	O
advanced	O
region	O
filling	O
options	O
of	O
PostScript	B-Language
.	O
</s>
<s>
In	O
order	O
to	O
take	O
full	O
advantage	O
of	O
PostScript	B-Language
printing	O
,	O
applications	O
on	O
the	O
computers	O
had	O
to	O
re-implement	O
those	O
features	O
using	O
the	O
host	O
platform	O
's	O
own	O
graphics	O
system	O
.	O
</s>
<s>
As	O
computer	O
power	O
grew	O
,	O
it	O
became	O
possible	O
to	O
host	O
the	O
PS	B-Language
system	O
in	O
the	O
computer	O
rather	O
than	O
the	O
printer	O
.	O
</s>
<s>
This	O
led	O
to	O
the	O
natural	O
evolution	O
of	O
PS	B-Language
from	O
a	O
printing	O
system	O
to	O
one	O
that	O
could	O
also	O
be	O
used	O
as	O
the	O
host	O
's	O
own	O
graphics	O
language	O
.	O
</s>
<s>
In	O
a	O
production	O
setting	O
,	O
using	O
PostScript	B-Language
as	O
a	O
display	O
system	O
meant	O
that	O
the	O
host	O
computer	O
could	O
render	O
low-resolution	O
to	O
the	O
screen	O
,	O
higher	O
resolution	B-Algorithm
to	O
the	O
printer	O
,	O
or	O
simply	O
send	O
the	O
PS	B-Language
code	O
to	O
a	O
smart	O
printer	O
for	O
offboard	O
printing	O
.	O
</s>
<s>
However	O
,	O
PostScript	B-Language
was	O
written	O
with	O
printing	O
in	O
mind	O
,	O
and	O
had	O
numerous	O
features	O
that	O
made	O
it	O
unsuitable	O
for	O
direct	O
use	O
in	O
an	O
interactive	O
display	O
system	O
.	O
</s>
<s>
In	O
particular	O
,	O
PS	B-Language
was	O
based	O
on	O
the	O
idea	O
of	O
collecting	O
up	O
PS	B-Language
commands	O
until	O
the	O
showpage	O
command	O
was	O
seen	O
,	O
at	O
which	O
point	O
all	O
of	O
the	O
commands	O
read	O
up	O
to	O
that	O
point	O
were	O
interpreted	B-Application
and	O
output	O
.	O
</s>
<s>
Nor	O
did	O
PS	B-Language
have	O
any	O
sort	O
of	O
interactivity	O
built	O
in	O
;	O
for	O
example	O
,	O
supporting	O
hit	O
detection	O
for	O
mouse	O
interactivity	O
obviously	O
did	O
not	O
apply	O
when	O
PS	B-Language
was	O
being	O
used	O
on	O
a	O
printer	O
.	O
</s>
<s>
When	O
Steve	O
Jobs	O
left	O
Apple	O
and	O
started	O
NeXT	O
,	O
he	O
pitched	O
Adobe	O
on	O
the	O
idea	O
of	O
using	O
PS	B-Language
as	O
the	O
display	O
system	O
for	O
his	O
new	O
workstation	B-Device
computers	I-Device
.	O
</s>
<s>
The	O
result	O
was	O
Display	O
PostScript	B-Language
,	O
or	O
DPS	O
.	O
</s>
<s>
DPS	O
added	O
basic	O
functionality	O
to	O
improve	O
performance	O
by	O
changing	O
many	O
string	O
lookups	O
into	O
32	O
bit	O
integers	O
,	O
adding	O
support	O
for	O
direct	O
output	O
with	O
every	O
command	O
,	O
and	O
adding	O
functions	O
to	O
allow	O
the	O
GUI	B-Application
to	O
inspect	O
the	O
diagram	O
.	O
</s>
<s>
Additionally	O
,	O
a	O
set	O
of	O
"	O
bindings	O
"	O
was	O
provided	O
to	O
allow	O
PS	B-Language
code	O
to	O
be	O
called	O
directly	O
from	O
the	O
C	B-Language
programming	I-Language
language	I-Language
.	O
</s>
<s>
NeXT	O
used	O
these	O
bindings	O
in	O
their	O
NeXTStep	B-Application
system	O
to	O
provide	O
an	O
object	B-Language
oriented	I-Language
graphics	O
system	O
.	O
</s>
<s>
Although	O
DPS	O
was	O
written	O
in	O
conjunction	O
with	O
NeXT	O
,	O
Adobe	O
sold	O
it	O
commercially	O
and	O
it	O
was	O
a	O
common	O
feature	O
of	O
most	O
Unix	B-Device
workstations	I-Device
in	O
the	O
1990s	O
.	O
</s>
<s>
Instead	O
of	O
DPS	O
's	O
concept	O
of	O
allowing	O
PS	B-Language
to	O
interact	O
with	O
C	B-Language
programs	I-Language
,	O
NeWS	O
instead	O
extended	O
PS	B-Language
into	O
a	O
language	O
suitable	O
for	O
running	O
the	O
entire	O
GUI	B-Application
of	O
a	O
computer	O
.	O
</s>
<s>
Sun	O
added	O
a	O
number	O
of	O
new	O
commands	O
for	O
timers	O
,	O
mouse	O
control	O
,	O
interrupts	O
and	O
other	O
systems	O
needed	O
for	O
interactivity	O
,	O
and	O
added	O
data	B-General_Concept
structures	I-General_Concept
and	O
language	O
elements	O
to	O
allow	O
it	O
to	O
be	O
completely	O
object	B-Language
oriented	I-Language
internally	O
.	O
</s>
<s>
A	O
complete	O
GUI	B-Application
,	O
three	O
in	O
fact	O
,	O
were	O
written	O
in	O
NeWS	O
and	O
provided	O
for	O
a	O
time	O
on	O
their	O
workstations	B-Device
.	O
</s>
<s>
However	O
,	O
the	O
ongoing	O
efforts	O
to	O
standardize	O
the	O
X11	B-Operating_System
system	O
led	O
to	O
its	O
introduction	O
and	O
widespread	O
use	O
on	O
Sun	O
systems	O
,	O
and	O
NeWS	O
never	O
became	O
widely	O
used	O
.	O
</s>
<s>
The	O
PDF	B-Application
and	O
PostScript	B-Language
share	O
the	O
same	O
imaging	O
model	O
and	O
both	O
documents	O
are	O
mutually	O
convertible	O
to	O
each	O
other	O
.	O
</s>
<s>
The	O
difference	O
between	O
the	O
PDF	B-Application
and	O
PostScript	B-Language
is	O
that	O
the	O
PDF	B-Application
lacks	O
the	O
general-purpose	O
programming	O
language	O
framework	O
of	O
the	O
PostScript	B-Language
language	I-Language
.	O
</s>
<s>
A	O
PDF	B-Application
document	O
is	O
a	O
static	O
data	B-General_Concept
structure	I-General_Concept
made	O
for	O
efficient	O
access	O
and	O
embeds	O
navigational	O
information	O
suitable	O
for	O
interactive	O
viewing	O
.	O
</s>
<s>
PostScript	B-Language
is	O
a	O
Turing-complete	O
programming	O
language	O
,	O
belonging	O
to	O
the	O
concatenative	B-Language
group	O
.	O
</s>
<s>
Typically	O
,	O
PostScript	B-Language
programs	O
are	O
not	O
produced	O
by	O
humans	O
,	O
but	O
by	O
other	O
programs	O
.	O
</s>
<s>
However	O
,	O
it	O
is	O
possible	O
to	O
write	O
computer	O
programs	O
in	O
PostScript	B-Language
just	O
like	O
any	O
other	O
programming	O
language	O
.	O
</s>
<s>
PostScript	B-Language
is	O
an	O
interpreted	B-Application
,	O
stack-based	B-Language
language	I-Language
similar	O
to	O
Forth	B-Application
but	O
with	O
strong	O
dynamic	O
typing	O
,	O
data	B-General_Concept
structures	I-General_Concept
inspired	O
by	O
those	O
found	O
in	O
Lisp	B-Language
,	O
scoped	B-Language
memory	I-Language
and	O
,	O
since	O
language	O
level	O
2	O
,	O
garbage	B-General_Concept
collection	I-General_Concept
.	O
</s>
<s>
The	O
language	O
syntax	O
uses	O
reverse	B-Application
Polish	I-Application
notation	O
,	O
which	O
makes	O
the	O
order	O
of	O
operations	O
unambiguous	O
,	O
but	O
reading	O
a	O
program	O
requires	O
some	O
practice	O
,	O
because	O
one	O
has	O
to	O
keep	O
the	O
layout	O
of	O
the	O
stack	B-Application
in	O
mind	O
.	O
</s>
<s>
Most	O
operators	O
(	O
what	O
other	O
languages	O
term	O
functions	O
)	O
take	O
their	O
arguments	O
from	O
the	O
stack	B-Application
,	O
and	O
place	O
their	O
results	O
onto	O
the	O
stack	B-Application
.	O
</s>
<s>
Literals	O
(	O
for	O
example	O
,	O
numbers	O
)	O
have	O
the	O
effect	O
of	O
placing	O
a	O
copy	O
of	O
themselves	O
on	O
the	O
stack	B-Application
.	O
</s>
<s>
Sophisticated	O
data	B-General_Concept
structures	I-General_Concept
can	O
be	O
built	O
on	O
the	O
array	O
and	O
dictionary	O
types	O
,	O
but	O
cannot	O
be	O
declared	O
to	O
the	O
type	O
system	O
,	O
which	O
sees	O
them	O
all	O
only	O
as	O
arrays	O
and	O
dictionaries	O
,	O
so	O
any	O
further	O
typing	O
discipline	O
to	O
be	O
applied	O
to	O
such	O
user-defined	O
"	O
types	O
"	O
is	O
left	O
to	O
the	O
code	O
that	O
implements	O
them	O
.	O
</s>
<s>
The	O
character	O
"	O
%	O
"	O
is	O
used	O
to	O
introduce	O
comments	O
in	O
PostScript	B-Language
programs	O
.	O
</s>
<s>
As	O
a	O
general	O
convention	O
,	O
every	O
PostScript	B-Language
program	O
should	O
start	O
with	O
the	O
characters	O
"	O
%	O
!	O
PS	B-Language
"	O
as	O
an	O
interpreter	B-Operating_System
directive	I-Operating_System
so	O
that	O
all	O
devices	O
will	O
properly	O
interpret	O
it	O
as	O
PostScript	B-Language
.	O
</s>
<s>
A	O
Hello	O
World	O
program	O
,	O
the	O
customary	O
way	O
to	O
show	O
a	O
small	O
example	O
of	O
a	O
complete	O
program	O
in	O
a	O
given	O
language	O
,	O
might	O
look	O
like	O
this	O
in	O
PostScript	B-Language
(	O
level	O
2	O
)	O
:	O
</s>
<s>
PostScript	B-Language
uses	O
the	O
point	O
as	O
its	O
unit	O
of	O
length	O
.	O
</s>
<s>
However	O
,	O
unlike	O
some	O
of	O
the	O
other	O
versions	O
of	O
the	O
point	O
,	O
PostScript	B-Language
uses	O
exactly	O
72	O
points	O
to	O
the	O
inch	O
.	O
</s>
<s>
Most	O
implementations	O
of	O
PostScript	B-Language
use	O
single-precision	O
reals	O
(	O
24-bit	O
mantissa	O
)	O
,	O
so	O
it	O
is	O
not	O
meaningful	O
to	O
use	O
more	O
than	O
9	O
decimal	O
digits	O
to	O
specify	O
a	O
real	O
number	O
,	O
and	O
performing	O
calculations	O
may	O
produce	O
unacceptable	O
round-off	O
errors	O
.	O
</s>
<s>
List	O
of	O
software	O
which	O
can	O
be	O
used	O
to	O
render	O
the	O
PostScript	B-Language
documents	O
:	O
</s>
