<s>
In	O
computer	B-General_Concept
science	I-General_Concept
,	O
runtime	B-Library
,	O
run	B-Library
time	I-Library
,	O
or	O
execution	B-Library
time	I-Library
is	O
the	O
final	O
phase	O
of	O
a	O
computer	B-Application
programs	I-Application
life	B-Application
cycle	I-Application
,	O
in	O
which	O
the	O
code	O
is	O
being	O
executed	B-General_Concept
on	O
the	O
computer	O
's	O
central	B-General_Concept
processing	I-General_Concept
unit	I-General_Concept
(	O
CPU	O
)	O
as	O
machine	B-Language
code	I-Language
.	O
</s>
<s>
In	O
other	O
words	O
,	O
"	O
runtime	B-Library
"	O
is	O
the	O
running	O
phase	O
of	O
a	O
program	O
.	O
</s>
<s>
A	O
runtime	B-Library
error	I-Library
is	O
detected	O
after	O
or	O
during	O
the	O
execution	O
(	O
running	O
state	O
)	O
of	O
a	O
program	O
,	O
whereas	O
a	O
compile-time	B-Application
error	I-Application
is	O
detected	O
by	O
the	O
compiler	B-Language
before	O
the	O
program	O
is	O
ever	O
executed	B-General_Concept
.	O
</s>
<s>
Type	O
checking	O
,	O
register	O
allocation	O
,	O
code	B-Application
generation	I-Application
,	O
and	O
code	O
optimization	O
are	O
typically	O
done	O
at	O
compile	B-Application
time	I-Application
,	O
but	O
may	O
be	O
done	O
at	B-Library
runtime	I-Library
depending	O
on	O
the	O
particular	O
language	O
and	O
compiler	B-Language
.	O
</s>
<s>
Many	O
other	O
runtime	B-Library
errors	I-Library
exist	O
and	O
are	O
handled	O
differently	O
by	O
different	O
programming	O
languages	O
,	O
such	O
as	O
division	B-Algorithm
by	I-Algorithm
zero	I-Algorithm
errors	O
,	O
domain	O
errors	O
,	O
array	B-Data_Structure
subscript	I-Data_Structure
out	I-Data_Structure
of	I-Data_Structure
bounds	I-Data_Structure
errors	O
,	O
arithmetic	B-Algorithm
underflow	I-Algorithm
errors	O
,	O
several	O
types	O
of	O
underflow	B-Algorithm
and	O
overflow	O
errors	O
,	O
and	O
many	O
other	O
runtime	B-Library
errors	I-Library
generally	O
considered	O
as	O
software	B-Error_Name
bugs	I-Error_Name
which	O
may	O
or	O
may	O
not	O
be	O
caught	O
and	O
handled	O
by	O
any	O
particular	O
computer	O
language	O
.	O
</s>
<s>
When	O
a	O
program	O
is	O
to	O
be	O
executed	B-General_Concept
,	O
a	O
loader	B-Operating_System
first	O
performs	O
the	O
necessary	O
memory	B-General_Concept
setup	O
and	O
links	O
the	O
program	O
with	O
any	O
dynamically	B-Application
linked	I-Application
libraries	B-Library
it	O
needs	O
,	O
and	O
then	O
the	O
execution	O
begins	O
starting	O
from	O
the	O
program	O
's	O
entry	B-Language
point	I-Language
.	O
</s>
<s>
In	O
some	O
cases	O
,	O
a	O
language	O
or	O
implementation	O
will	O
have	O
these	O
tasks	O
done	O
by	O
the	O
language	O
runtime	B-Library
instead	O
,	O
though	O
this	O
is	O
unusual	O
in	O
mainstream	O
languages	O
on	O
common	O
consumer	O
operating	O
systems	O
.	O
</s>
<s>
Some	O
program	O
debugging	O
can	O
only	O
be	O
performed	O
(	O
or	O
is	O
more	O
efficient	O
or	O
accurate	O
when	O
performed	O
)	O
at	B-Library
runtime	I-Library
.	O
</s>
<s>
Logic	B-General_Concept
errors	I-General_Concept
and	O
array	B-Data_Structure
bounds	I-Data_Structure
checking	I-Data_Structure
are	O
examples	O
.	O
</s>
<s>
For	O
this	O
reason	O
,	O
some	O
programming	B-Error_Name
bugs	I-Error_Name
are	O
not	O
discovered	O
until	O
the	O
program	O
is	O
tested	O
in	O
a	O
production	O
environment	O
with	O
real	O
data	O
,	O
despite	O
sophisticated	O
compile-time	B-Application
checking	O
and	O
pre-release	O
testing	O
.	O
</s>
<s>
In	O
this	O
case	O
,	O
the	O
end-user	O
may	O
encounter	O
a	O
"	O
runtime	B-Library
error	I-Library
"	O
message	O
.	O
</s>
<s>
Exception	B-General_Concept
handling	I-General_Concept
is	O
one	O
language	O
feature	O
designed	O
to	O
handle	O
runtime	B-Library
errors	I-Library
,	O
providing	O
a	O
structured	O
way	O
to	O
catch	O
completely	O
unexpected	O
situations	O
as	O
well	O
as	O
predictable	O
errors	O
or	O
unusual	O
results	O
without	O
the	O
amount	O
of	O
inline	O
error	O
checking	O
required	O
of	O
languages	O
without	O
it	O
.	O
</s>
<s>
More	O
recent	O
advancements	O
in	O
runtime	B-Device
engines	I-Device
enable	O
automated	B-Language
exception	I-Language
handling	I-Language
which	O
provides	O
"	O
root-cause	O
"	O
debug	O
information	O
for	O
every	O
exception	O
of	O
interest	O
and	O
is	O
implemented	O
independent	O
of	O
the	O
source	O
code	O
,	O
by	O
attaching	O
a	O
special	O
software	O
product	O
to	O
the	O
runtime	B-Device
engine	I-Device
.	O
</s>
