<s>
A	O
software	B-Application
engine	I-Application
is	O
a	O
core	O
component	O
of	O
a	O
complex	O
software	O
system	O
.	O
</s>
<s>
Alternate	O
phrases	O
include	O
"	O
software	O
core	O
"	O
and	O
"	O
software	O
core	B-Application
engine	I-Application
"	O
,	O
or	O
just	O
"	O
core	B-Application
engine	I-Application
"	O
.	O
</s>
<s>
Thus	O
a	O
software	B-Application
engine	I-Application
is	O
a	O
complex	O
subsystem	O
.	O
</s>
<s>
There	O
is	O
no	O
formal	O
guideline	O
for	O
what	O
should	O
be	O
called	O
an	O
engine	O
,	O
but	O
the	O
term	O
has	O
become	O
entrenched	O
in	O
the	O
software	B-Application
industry	I-Application
.	O
</s>
<s>
Notable	O
examples	O
are	O
database	B-General_Concept
engine	I-General_Concept
,	O
graphics	O
engine	O
,	O
physics	O
engine	O
,	O
search	B-Application
engine	I-Application
,	O
plotting	O
engine	O
,	O
and	O
game	O
engine	O
.	O
</s>
<s>
Moreover	O
,	O
a	O
web	B-Application
browser	I-Application
actually	O
has	O
two	O
components	O
referred	O
to	O
as	O
engines	O
:	O
the	O
browser	B-Protocol
engine	I-Protocol
and	O
JavaScript	B-Language
engine	I-Language
.	O
</s>
<s>
One	O
seeming	O
outlier	O
is	O
a	O
search	B-Application
engine	I-Application
,	O
such	O
as	O
Google	B-Application
Search	I-Application
,	O
because	O
it	O
is	O
a	O
stand-alone	O
service	O
provided	O
to	O
end	O
users	O
.	O
</s>
<s>
However	O
,	O
for	O
the	O
search	O
provider	O
,	O
the	O
engine	O
is	O
part	O
of	O
a	O
distributed	B-Architecture
computing	I-Architecture
system	O
that	O
can	O
encompass	O
many	O
data	B-Operating_System
centers	I-Operating_System
throughout	O
the	O
world	O
.	O
</s>
<s>
There	O
is	O
a	O
difference	O
between	O
Google	B-Application
the	O
end-user	O
application	O
and	O
Google	B-Application
the	O
search	B-Application
engine	I-Application
.	O
</s>
<s>
As	O
an	O
end	O
user	O
,	O
search	O
is	O
done	O
via	O
a	O
user	O
interface	O
,	O
generally	O
a	O
browser	B-Application
,	O
which	O
talks	O
to	O
the	O
"	O
engine	O
"	O
.	O
</s>
<s>
Prior	O
to	O
the	O
Google	B-Application
online	O
search	B-Application
service	I-Application
,	O
there	O
had	O
been	O
multiple	O
search	B-Application
engines	I-Application
that	O
were	O
indeed	O
packaged	O
as	O
software	O
modules	O
.	O
</s>
<s>
Long	O
before	O
Google	B-Application
,	O
there	O
were	O
online	O
dialup	O
services	O
that	O
used	O
third	O
party	O
search	B-Application
engines	I-Application
,	O
such	O
as	O
Congressional	O
Quarterly	O
's	O
Washington	O
Alert	O
II	O
service	O
.	O
</s>
<s>
Before	O
that	O
there	O
were	O
many	O
desktop	O
products	O
that	O
included	O
third	O
party	O
search	B-Application
engines	I-Application
,	O
especially	O
CD-ROM	O
based	O
encyclopedias	O
from	O
Grollier	O
,	O
Comptons	O
,	O
Bertelsmann	O
,	O
and	O
many	O
others	O
.	O
</s>
<s>
Most	O
of	O
the	O
early	O
search	B-Application
engine	I-Application
companies	O
,	O
such	O
as	O
Personal	O
Library	O
Software	O
and	O
their	O
CPL	O
product	O
,	O
are	O
long	O
gone	O
.	O
</s>
<s>
One	O
of	O
the	O
earliest	O
Web	B-Application
search	I-Application
services	O
,	O
perhaps	O
the	O
first	O
,	O
was	O
WebCrawler	O
.	O
</s>
<s>
It	O
was	O
based	O
on	O
the	O
CPL	O
search	B-Application
engine	I-Application
library	O
from	O
Personal	O
Library	O
Software	O
.	O
</s>
<s>
One	O
might	O
call	O
the	B-Language
C	I-Language
standard	I-Language
library	I-Language
an	O
"	O
engine	O
"	O
,	O
but	O
it	O
does	O
not	O
really	O
have	O
a	O
focus	O
other	O
than	O
to	O
provide	O
a	O
broad	O
range	O
of	O
low	O
level	O
services	O
.	O
</s>
