<s>
A	O
blueprint	B-Application
is	O
a	O
reproduction	O
of	O
a	O
technical	B-Application
drawing	I-Application
or	O
engineering	B-Architecture
drawing	I-Architecture
using	O
a	O
contact	O
print	O
process	O
on	O
light-sensitive	O
sheets	O
.	O
</s>
<s>
The	O
blueprint	B-Application
process	O
was	O
characterized	O
by	O
white	O
lines	O
on	O
a	O
blue	O
background	O
,	O
a	O
negative	O
of	O
the	O
original	O
.	O
</s>
<s>
It	O
was	O
first	O
largely	O
displaced	O
by	O
the	O
diazo	O
whiteprint	B-Application
process	O
,	O
and	O
later	O
by	O
large-format	O
xerographic	O
photocopiers	O
.	O
</s>
<s>
The	O
term	O
blueprint	B-Application
continues	O
to	O
be	O
used	O
less	O
formally	O
to	O
refer	O
to	O
any	O
floor	B-Application
plan	I-Application
(	O
and	O
even	O
less	O
formally	O
,	O
any	O
type	O
of	O
plan	O
)	O
.	O
</s>
<s>
Practising	O
engineers	O
,	O
architects	B-Application
,	O
and	O
drafters	O
often	O
call	O
them	O
"	O
drawings	O
"	O
,	O
“	O
prints	O
”	O
,	O
or	O
“	O
plans	O
”	O
.	O
</s>
<s>
It	O
has	O
almost	O
entirely	O
been	O
replaced	O
with	O
digital	O
computer-aided	O
construction	B-Architecture
drawings	I-Architecture
.	O
</s>
<s>
The	O
blueprint	B-Application
process	O
is	O
based	O
on	O
a	O
photosensitive	O
ferric	O
compound	O
.	O
</s>
<s>
Engineers	O
and	O
architects	B-Application
drew	O
their	O
designs	O
on	O
cartridge	O
paper	O
;	O
these	O
were	O
then	O
traced	O
on	O
to	O
tracing	O
paper	O
using	O
India	O
ink	O
for	O
reproduction	O
whenever	O
needed	O
.	O
</s>
<s>
Introduction	O
of	O
the	O
blueprint	B-Application
process	O
eliminated	O
the	O
expense	O
of	O
photolithographic	O
reproduction	O
or	O
of	O
hand-tracing	O
of	O
original	O
drawings	O
.	O
</s>
<s>
By	O
the	O
later	O
1890s	O
in	O
American	O
architectural	O
offices	O
,	O
a	O
blueprint	B-Application
was	O
one-tenth	O
the	O
cost	O
of	O
a	O
hand-traced	O
reproduction	O
.	O
</s>
<s>
The	O
blueprint	B-Application
process	O
is	O
still	O
used	O
for	O
special	O
artistic	O
and	O
photographic	O
effects	O
,	O
on	O
paper	O
and	O
fabrics	O
.	O
</s>
<s>
Various	O
base	O
materials	O
have	O
been	O
used	O
for	O
blueprints	B-Application
.	O
</s>
<s>
Traditional	O
blueprints	B-Application
became	O
obsolete	O
when	O
less	O
expensive	O
printing	O
methods	O
and	O
digital	O
displays	O
became	O
available	O
.	O
</s>
<s>
In	O
the	O
early	O
1940s	O
,	O
cyanotype	O
blueprint	B-Application
began	O
to	O
be	O
supplanted	O
by	O
diazo	B-Application
prints	I-Application
,	O
also	O
known	O
as	O
whiteprints	B-Application
.	O
</s>
<s>
Diazo	B-Application
prints	I-Application
remained	O
in	O
use	O
until	O
they	O
were	O
replaced	O
by	O
xerographic	O
print	O
processes	O
.	O
</s>
<s>
As	O
computer-aided	B-Application
design	I-Application
techniques	O
came	O
into	O
use	O
,	O
the	O
designs	O
were	O
printed	O
directly	O
using	O
a	O
computer	O
printer	O
or	O
plotter	B-Operating_System
.	O
</s>
<s>
In	O
most	O
computer-aided	B-Application
design	I-Application
of	O
parts	O
to	O
be	O
machined	O
,	O
paper	O
is	O
avoided	O
altogether	O
,	O
and	O
the	O
finished	O
design	O
is	O
an	O
image	O
on	O
the	O
computer	O
display	O
.	O
</s>
<s>
The	O
computer-aided	B-Application
design	I-Application
program	O
generates	O
a	O
computer	O
numerical	O
control	O
sequence	O
from	O
the	O
approved	O
design	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
construction	O
plans	O
,	O
such	O
as	O
road	O
work	O
or	O
erecting	O
a	O
building	O
,	O
the	O
supervising	O
workers	O
may	O
view	O
the	O
"	O
blueprints	B-Application
"	O
directly	O
on	O
displays	O
,	O
rather	O
than	O
using	O
printed	O
paper	O
sheets	O
.	O
</s>
<s>
These	O
displays	O
include	O
mobile	O
devices	O
,	O
such	O
as	O
smartphones	B-Application
or	O
tablets	B-Device
.	O
</s>
<s>
Construction	O
crews	O
use	O
software	O
in	O
the	O
field	O
to	O
edit	O
,	O
share	O
,	O
and	O
view	O
blueprint	B-Application
documents	O
in	O
real-time	O
.	O
</s>
<s>
Many	O
of	O
the	O
original	O
paper	O
blueprints	B-Application
are	O
archived	O
since	O
they	O
are	O
still	O
in	O
use	O
.	O
</s>
<s>
Most	O
buildings	O
and	O
roads	O
constructed	O
before	O
1990	O
will	O
only	O
have	O
paper	O
blueprints	B-Application
,	O
not	O
digital	O
.	O
</s>
