<s>
The	O
term	O
dead	B-Application
code	I-Application
has	O
multiple	O
definitions	O
.	O
</s>
<s>
In	O
some	O
areas	O
of	O
computer	B-General_Concept
programming	I-General_Concept
,	O
dead	B-Application
code	I-Application
is	O
a	O
section	O
in	O
the	O
source	O
code	O
of	O
a	O
program	O
which	O
is	O
executed	O
but	O
whose	O
result	O
is	O
never	O
used	O
in	O
any	O
other	O
computation	O
.	O
</s>
<s>
The	O
execution	O
of	O
dead	B-Application
code	I-Application
wastes	O
computation	O
time	O
and	O
memory	O
.	O
</s>
<s>
While	O
the	O
result	O
of	O
a	O
dead	O
computation	O
may	O
never	O
be	O
used	O
,	O
it	O
may	O
raise	O
exceptions	B-General_Concept
or	O
affect	O
some	O
global	O
state	O
,	O
thus	O
removal	O
of	O
such	O
code	O
may	O
change	O
the	O
output	O
of	O
the	O
program	O
and	O
introduce	O
unintended	O
bugs	B-Error_Name
.	O
</s>
<s>
Compiler	B-Application
optimizations	I-Application
are	O
typically	O
conservative	O
in	O
their	O
approach	O
to	O
dead-code	O
removal	O
if	O
there	O
is	O
any	O
ambiguity	O
as	O
to	O
whether	O
removal	O
of	O
the	O
dead	B-Application
code	I-Application
will	O
affect	O
the	O
program	O
output	O
.	O
</s>
<s>
Therefore	O
,	O
the	O
removal	O
of	O
the	O
dead	B-Application
code	I-Application
may	O
change	O
the	O
output	O
of	O
the	O
program	O
.	O
</s>
<s>
Dead-code	O
elimination	O
is	O
a	O
form	O
of	O
compiler	B-Application
optimization	I-Application
in	O
which	O
dead	B-Application
code	I-Application
is	O
removed	O
from	O
a	O
program	O
.	O
</s>
<s>
Dead	B-Application
code	I-Application
analysis	O
can	O
be	O
performed	O
using	O
live-variable	O
analysis	O
,	O
a	O
form	O
of	O
static-code	O
analysis	O
and	O
data-flow	O
analysis	O
.	O
</s>
<s>
In	O
large	O
programming	O
projects	O
,	O
it	O
is	O
sometimes	O
difficult	O
to	O
recognize	O
and	O
eliminate	O
dead	B-Application
code	I-Application
,	O
particularly	O
when	O
entire	O
modules	O
become	O
dead	O
.	O
</s>
<s>
Some	O
IDEs	O
(	O
such	O
as	O
Xcode	O
,	O
Visual	O
Studio	O
2010	O
and	O
Eclipse	O
Galileo	O
)	O
have	O
the	O
ability	O
to	O
locate	O
dead	B-Application
code	I-Application
during	O
the	O
compiling	O
stage	O
.	O
</s>
<s>
While	O
most	O
optimization	O
techniques	O
seek	O
to	O
remove	O
dead	B-Application
code	I-Application
in	O
an	O
implementation	O
,	O
in	O
extreme	O
forms	O
of	O
optimization	O
for	O
size	O
it	O
may	O
sometimes	O
be	O
desirable	O
to	O
deliberately	O
introduce	O
and	O
carefully	O
shape	O
seemingly	O
dead	B-Application
code	I-Application
,	O
when	O
it	O
allows	O
to	O
fold	O
otherwise	O
unrelated	O
code	O
sections	O
together	O
(	O
and	O
thereby	O
reduce	O
their	O
combined	O
size	O
)	O
so	O
that	O
the	O
extra	O
code	O
will	O
effectively	O
not	O
harm	O
the	O
first	O
path	O
of	O
execution	O
through	O
the	O
code	O
but	O
is	O
used	O
to	O
carry	O
out	O
the	O
actions	O
necessary	O
for	O
the	O
alternative	O
paths	O
of	O
execution	O
,	O
for	O
which	O
other	O
sections	O
of	O
the	O
code	O
may	O
become	O
dead	B-Application
code	I-Application
.	O
</s>
<s>
On	O
a	O
more	O
functional	O
level	O
,	O
this	O
can	O
be	O
seen	O
as	O
both	O
,	O
artificially	O
introduction	O
of	O
harmless/useful	O
side-effects	O
and	O
reduction	O
of	O
the	O
redundancy	O
of	O
the	O
code	O
,	O
but	O
it	O
can	O
also	O
be	O
used	O
down	O
to	O
opcode	O
level	O
in	O
order	O
to	O
allow	O
the	O
usage	O
of	O
shorter	O
instructions	O
,	O
which	O
would	O
not	O
be	O
possible	O
when	O
folding	O
code	O
sequences	O
without	O
the	O
concerted	O
introduction	O
of	O
side-effects	O
caused	O
by	O
the	O
dead	B-Application
code	I-Application
.	O
</s>
