<s>
OTcl	B-Language
usually	O
refers	O
to	O
an	O
object	B-Language
oriented	I-Language
extension	O
of	O
Tcl	B-Operating_System
created	O
by	O
David	O
Wetherall	O
at	O
MIT	O
(	O
hence	O
the	O
name	O
OTcl	B-Language
—	O
short	O
for	O
MIT	O
Object	O
Tcl	B-Operating_System
)	O
.	O
</s>
<s>
It	O
is	O
used	O
in	O
network	O
simulator	O
(	O
NS-2	O
)	O
and	O
usually	O
run	O
under	O
Unix	B-Application
environment	O
.	O
</s>
<s>
This	O
was	O
later	O
extended	O
into	O
XOTcl	B-Language
.	O
</s>
<s>
OTcl	B-Language
may	O
also	O
refer	O
to	O
the	O
unrelated	O
IXI	O
Object	O
Tcl	B-Operating_System
extension	O
by	O
Dean	O
Sheenan	O
.	O
</s>
<s>
These	O
object	O
Tcl	B-Operating_System
extensions	O
predate	O
the	O
more	O
popular	O
incr	B-Application
Tcl	I-Application
.	O
</s>
<s>
The	O
variable	O
self	O
is	O
pointer	O
to	O
the	O
class	O
it	O
is	O
used	O
in	O
and	O
is	O
equivalent	O
to	O
variable	O
this	O
of	O
C++	B-Language
/Java	O
.	O
</s>
<s>
TclCL	O
(	O
Tcl	B-Operating_System
with	O
classes	O
)	O
is	O
a	O
Tcl/C	O
++	O
interface	O
used	O
by	O
Mash	O
,	O
vic	O
,	O
vat	O
,	O
rtp_play	O
,	O
ns	B-Language
,	O
and	O
nam	O
.	O
</s>
<s>
It	O
provides	O
a	O
layer	O
of	O
C++	B-Language
glue	O
over	O
OTcl	B-Language
.	O
</s>
