<s>
On-line	B-Application
Debugging	I-Application
Tool	I-Application
(	O
ODT	O
)	O
is	O
a	O
family	O
of	O
several	O
debugger	B-Application
programs	O
developed	O
for	O
Digital	O
Equipment	O
Corporation	O
(	O
DEC	O
)	O
hardware	O
.	O
</s>
<s>
Various	O
operating	B-General_Concept
systems	I-General_Concept
including	O
OS/8	B-Operating_System
,	O
RT-11	B-Operating_System
,	O
RSX-11	B-Application
,	O
and	O
RSTS/E	B-Operating_System
implement	O
ODT	O
,	O
as	O
did	O
the	O
firmware	B-Application
console	O
of	O
all	O
of	O
the	O
LSI-11-family	O
processors	O
including	O
the	O
11/03	O
,	O
11/23/24	O
,	O
11/53	O
,	O
11/73	B-Device
,	O
and	O
11/83/84	O
.	O
</s>
<s>
The	O
debugger	B-Application
allows	O
access	O
to	O
memory	O
using	O
octal	O
addresses	O
and	O
data	O
.	O
</s>
<s>
Within	O
the	O
software	O
systems	O
,	O
the	O
debugger	B-Application
accesses	O
the	O
process	O
's	O
address	O
space	O
.	O
</s>
<s>
DEC	O
's	O
line	O
of	O
PDP-11	O
processors	O
do	O
not	O
implement	O
virtual	B-Architecture
memory	I-Architecture
,	O
from	O
an	O
operating	B-General_Concept
system	I-General_Concept
perspective	O
,	O
but	O
instead	O
work	O
in	O
a	O
fixed	O
address	O
space	O
,	O
which	O
is	O
mapped	O
into	O
a	O
unified	O
view	O
of	O
the	O
program	O
's	O
address	O
space	O
,	O
using	O
an	O
Active	O
Page	O
Register	O
(	O
APR	O
)	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
RSTS/E	B-Operating_System
,	O
this	O
usually	O
means	O
that	O
a	O
Runtime	O
System	O
,	O
or	O
RTS	O
,	O
maps	O
to	O
the	O
upper	O
portion	O
of	O
the	O
address	O
space	O
and	O
a	O
user	O
program	O
resides	O
in	O
the	O
lower	O
portion	O
of	O
the	O
address	O
space	O
.	O
</s>
<s>
The	O
RTS	O
provides	O
code	O
to	O
support	O
access	O
to	O
the	O
Operating	B-General_Concept
System	I-General_Concept
,	O
on	O
behalf	O
of	O
the	O
user	O
program	O
;	O
the	O
RTS	O
itself	O
stores	O
any	O
of	O
its	O
non-static	O
data	O
in	O
the	O
address	O
space	O
of	O
the	O
user	O
program	O
,	O
because	O
the	O
RTS	O
is	O
typically	O
read-only	O
.	O
</s>
<s>
The	O
operating	B-General_Concept
system	I-General_Concept
loads	O
a	O
single	O
copy	O
of	O
the	O
RTS	O
and	O
this	O
is	O
mapped	O
to	O
any	O
user	O
program	O
that	O
requires	O
that	O
RTS	O
.	O
</s>
<s>
The	O
RT11	B-Operating_System
RTS	O
occupies	O
4KiB	O
,	O
so	O
a	O
user	O
program	O
,	O
like	O
the	O
RT11-based	O
Peripheral	O
Interchange	O
Program	O
(	O
PIP	O
)	O
,	O
can	O
expand	O
to	O
a	O
maximum	O
of	O
28KiB	O
.	O
</s>
<s>
The	O
firmware	B-Application
console	O
implementation	O
accesses	O
physical	O
memory	O
.	O
</s>
<s>
ODT	O
is	O
a	O
non-symbolic	O
debugger	O
and	O
implements	O
similar	O
functionality	O
to	O
Advanced	B-Application
Debugger	I-Application
(	O
adb	O
)	O
on	O
Unix	B-Application
systems	I-Application
.	O
</s>
<s>
The	O
RSX-11M-Plus	O
ODT	O
is	O
essentially	O
a	O
superset	O
of	O
all	O
other	O
ODT	O
implementations	O
.	O
</s>
<s>
Addresses	O
in	O
the	O
ODT	O
debugger	B-Application
are	O
16-bit	O
addresses	O
in	O
the	O
mode	O
in	O
which	O
ODT	O
is	O
operating	O
,	O
not	O
the	O
physical	O
addresses	O
used	O
with	O
console	O
ODT	O
.	O
</s>
<s>
The	O
PDP-8	B-Device
'	O
s	O
OS/8	B-Operating_System
operating	B-General_Concept
system	I-General_Concept
's	O
ODT	O
command	O
invokes	O
its	O
Octal	B-Application
Debugging	I-Application
Technique	I-Application
tool	O
.	O
</s>
