<s>
OpenSees	B-Application
allows	O
users	O
to	O
create	O
finite	B-Application
element	I-Application
applications	O
for	O
simulating	O
the	O
response	O
of	O
structural	O
and	O
geotechnical	O
systems	O
subjected	O
to	O
earthquakes	O
.	O
</s>
<s>
OpenSees	B-Application
is	O
primarily	O
written	O
in	O
C++	B-Language
and	O
uses	O
several	O
Fortran	B-Application
numerical	O
libraries	O
for	O
linear	O
equation	O
solving	O
.	O
</s>
<s>
The	O
UC	O
Regents	O
hold	O
the	O
copyright	O
for	O
OpenSees	B-Application
to	O
be	O
used	O
in	O
commercial	O
distribution	O
.	O
</s>
<s>
Users	O
of	O
OpenSees	B-Application
create	O
applications	O
by	O
writing	O
scripts	O
in	O
either	O
the	O
Tcl	B-Operating_System
or	O
Python	B-Language
programming	I-Language
language	I-Language
.	O
</s>
<s>
OpenSees	B-Application
developers	O
manage	O
the	O
source	O
code	O
at	O
.	O
</s>
<s>
The	O
proper	O
acronym	O
capitalization	O
for	O
the	O
"	O
Open	O
System	O
for	O
Earthquake	O
Engineering	O
Simulation	O
"	O
is	O
OpenSees	B-Application
,	O
as	O
opposed	O
to	O
OpenSEES	B-Application
.	O
</s>
<s>
This	O
reflects	O
the	O
same	O
unconventional	O
capitalization	O
of	O
Tcl	B-Operating_System
.	O
</s>
<s>
Prior	O
to	O
taking	O
on	O
the	O
name	O
"	O
OpenSees	B-Application
,	O
"	O
the	O
framework	O
was	O
simply	O
called	O
"	O
G3	O
"	O
in	O
reference	O
to	O
the	O
name	O
of	O
the	O
research	O
group	O
tasked	O
with	O
simulation	O
development	O
.	O
</s>
<s>
The	O
doctoral	O
thesis	O
of	O
Frank	O
McKenna	O
on	O
parallel	O
object-oriented	B-Language
structural	O
analysis	O
formed	O
the	O
basis	O
for	O
"	O
G3.	O
"	O
</s>
