<s>
In	O
computing	O
,	O
a	O
resident	B-Application
monitor	I-Application
is	O
a	O
type	O
of	O
system	B-Application
software	I-Application
program	O
that	O
was	O
used	O
in	O
many	O
early	O
computers	O
from	O
the	O
1950s	O
to	O
1970s	O
.	O
</s>
<s>
It	O
can	O
be	O
considered	O
a	O
precursor	O
to	O
the	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
Because	O
memory	O
was	O
very	O
limited	O
on	O
those	O
systems	O
,	O
the	O
resident	B-Application
monitor	I-Application
was	O
often	O
little	O
more	O
than	O
a	O
stub	O
that	O
would	O
gain	O
control	O
at	O
the	O
end	O
of	O
a	O
job	O
and	O
load	O
a	O
non-resident	O
portion	O
to	O
perform	O
required	O
job	O
cleanup	O
and	O
setup	O
tasks	O
.	O
</s>
<s>
On	O
a	O
general-use	O
computer	O
using	O
punched	B-Architecture
card	I-Architecture
input	O
,	O
the	O
resident	B-Application
monitor	I-Application
governed	O
the	O
machine	O
before	O
and	O
after	O
each	O
job	B-General_Concept
control	I-General_Concept
card	O
was	O
executed	O
,	O
loaded	O
and	O
interpreted	O
each	O
control	O
card	O
,	O
and	O
acted	O
as	O
a	O
job	O
sequencer	O
for	O
batch	B-General_Concept
processing	I-General_Concept
operations	O
.	O
</s>
<s>
The	O
resident	B-Application
monitor	I-Application
could	O
clear	O
memory	O
from	O
the	O
last	O
used	O
program	O
(	O
with	O
the	O
exception	O
of	O
itself	O
)	O
,	O
load	O
programs	O
,	O
search	O
for	O
program	O
data	O
and	O
maintain	O
standard	O
input-output	O
routines	O
in	O
memory	O
.	O
</s>
<s>
Similar	O
system	B-Application
software	I-Application
layers	O
were	O
typically	O
in	O
use	O
in	O
the	O
early	O
days	O
of	O
the	O
later	O
minicomputers	B-Architecture
and	O
microcomputers	B-Architecture
before	O
they	O
gained	O
the	O
power	O
to	O
support	O
full	O
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
Resident	B-Application
monitor	I-Application
functionality	O
is	O
present	O
in	O
many	O
embedded	O
systems	O
,	O
boot	O
loaders	O
,	O
and	O
various	O
embedded	O
command	O
lines	O
.	O
</s>
<s>
The	O
original	O
functions	O
present	O
in	O
all	O
resident	B-Application
monitors	I-Application
are	O
augmented	O
with	O
present-day	O
functions	O
dealing	O
with	O
boot	O
time	O
hardware	O
,	O
disks	O
,	O
ethernet	O
,	O
wireless	O
controllers	O
,	O
etc	O
.	O
</s>
<s>
Such	O
a	O
resident	B-Application
monitor	I-Application
is	O
frequently	O
called	O
a	O
debugger	O
,	O
boot	O
loader	O
,	O
command-line	O
interface	O
(	O
CLI	O
)	O
,	O
etc	O
.	O
</s>
<s>
The	O
original	O
meaning	O
of	O
serial-accessed	O
or	O
terminal-accessed	O
resident	B-Application
monitor	I-Application
is	O
not	O
frequently	O
used	O
,	O
although	O
the	O
functionality	O
remained	O
the	O
same	O
,	O
and	O
was	O
augmented	O
.	O
</s>
<s>
Typical	O
functions	O
of	O
a	O
resident	B-Application
monitor	I-Application
include	O
examining	O
and	O
editing	O
ram	O
and/or	O
ROM	O
(	O
including	O
flash	O
EEPROM	O
)	O
and	O
sometimes	O
special	O
function	O
registers	O
,	O
the	O
ability	O
to	O
jump	O
into	O
code	O
at	O
a	O
specified	O
address	O
,	O
the	O
ability	O
to	O
call	O
code	O
at	O
a	O
given	O
address	O
,	O
the	O
ability	O
to	O
fill	O
an	O
address	O
range	O
with	O
a	O
constant	O
such	O
as	O
0x00	O
,	O
and	O
several	O
others	O
.	O
</s>
<s>
More	O
advanced	O
functions	O
include	O
local	O
disassembly	O
to	O
processor	O
assembly	B-Language
language	I-Language
instructions	O
,	O
and	O
even	O
assembly	O
and	O
writing	O
into	O
flash	O
memory	O
from	O
code	O
typed	O
by	O
the	O
operator	O
.	O
</s>
<s>
For	O
embedded	O
processors	O
,	O
many	O
"	O
in-circuit	O
debuggers	O
"	O
with	O
software-only	O
mode	O
use	O
resident	B-Application
monitor	I-Application
concepts	O
and	O
functions	O
that	O
are	O
frequently	O
accessed	O
by	O
a	O
GUI	O
IDE	O
.	O
</s>
<s>
They	O
are	O
not	O
different	O
from	O
the	O
traditionally	O
serial	O
line	O
accessed	O
resident	B-Application
monitor	I-Application
command	O
lines	O
,	O
but	O
users	O
are	O
not	O
aware	O
of	O
this	O
.	O
</s>
<s>
At	O
the	O
latest	O
,	O
developers	O
and	O
advanced	O
users	O
will	O
discover	O
these	O
low	O
level	O
embedded	O
resident	B-Application
monitor	I-Application
functions	O
when	O
writing	O
low	O
level	O
API	O
code	O
on	O
a	O
host	O
to	O
communicate	O
with	O
an	O
embedded	O
target	O
for	O
debugging	O
and	O
code	O
test	O
case	O
running	O
.	O
</s>
<s>
In	O
general	O
,	O
most	O
current	O
resident	B-Application
monitors	I-Application
for	O
embedded	O
computing	O
can	O
be	O
compiled	O
according	O
to	O
various	O
memory	O
constraints	O
,	O
from	O
small	O
and	O
minimalistic	O
,	O
to	O
large	O
,	O
filling	O
up	O
to	O
25%	O
of	O
the	O
code	O
space	O
available	O
on	O
an	O
AVR	O
ATmega328	B-Device
processor	O
with	O
32	O
kilobytes	O
of	O
flash	O
memory	O
,	O
for	O
example	O
.	O
</s>
<s>
In	O
many	O
cases	O
resident	B-Application
monitors	I-Application
can	O
be	O
a	O
step	O
up	O
from	O
"	O
printf	O
debugging	O
"	O
and	O
are	O
very	O
helpful	O
when	O
developing	O
on	O
a	O
budget	O
that	O
does	O
not	O
allow	O
a	O
proper	O
hardware	O
in-circuit	O
debugger	O
(	O
ICD	O
)	O
to	O
be	O
used	O
.	O
</s>
