<s>
Data	B-Application
Display	I-Application
Debugger	I-Application
(	O
GNU	B-Application
DDD	I-Application
)	O
is	O
a	O
graphical	B-Application
user	I-Application
interface	I-Application
(	O
using	O
the	O
Motif	B-Application
toolkit	I-Application
)	O
for	O
command-line	O
debuggers	O
such	O
as	O
GDB	B-Language
,	O
DBX	B-Application
,	O
JDB	O
,	O
HP	O
Wildebeest	O
Debugger	O
,	O
XDB	O
,	O
the	O
Perl	B-Language
debugger	O
,	O
the	O
Bash	B-Operating_System
debugger	O
,	O
the	O
Python	B-Language
debugger	O
,	O
and	O
the	O
GNU	O
Make	O
debugger	O
.	O
</s>
<s>
DDD	O
is	O
part	O
of	O
the	B-Application
GNU	I-Application
Project	I-Application
and	O
distributed	O
as	O
free	B-Application
software	I-Application
under	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
.	O
</s>
<s>
DDD	O
has	O
GUI	B-Application
front-end	O
features	O
such	O
as	O
viewing	O
source	O
texts	O
and	O
its	O
interactive	O
graphical	O
data	O
display	O
,	O
where	O
data	O
structures	O
are	O
displayed	O
as	O
graphs	O
.	O
</s>
<s>
DDD	O
is	O
used	O
primarily	O
on	O
Unix	B-Application
systems	I-Application
,	O
and	O
its	O
usefulness	O
is	O
complemented	O
by	O
many	O
open	O
source	O
plug-ins	O
available	O
for	O
it	O
.	O
</s>
