<s>
A	O
software	B-Error_Name
bug	I-Error_Name
is	O
an	O
error	O
,	O
flaw	O
or	O
fault	B-General_Concept
in	O
the	O
design	B-Architecture
,	O
development	O
,	O
or	O
operation	O
of	O
computer	B-Application
software	I-Application
that	O
causes	O
it	O
to	O
produce	O
an	O
incorrect	O
or	O
unexpected	O
result	O
,	O
or	O
to	O
behave	O
in	O
unintended	O
ways	O
.	O
</s>
<s>
The	O
process	O
of	O
finding	O
and	O
correcting	O
bugs	B-Error_Name
is	O
termed	O
"	O
debugging	O
"	O
and	O
often	O
uses	O
formal	O
techniques	O
or	O
tools	O
to	O
pinpoint	O
bugs	B-Error_Name
.	O
</s>
<s>
Since	O
the	O
1950s	O
,	O
some	O
computer	O
systems	O
have	O
been	O
designed	O
to	O
deter	O
,	O
detect	O
or	O
auto-correct	O
various	O
computer	B-Error_Name
bugs	I-Error_Name
during	O
operations	O
.	O
</s>
<s>
Bugs	B-Error_Name
in	O
software	O
can	O
arise	O
from	O
mistakes	O
and	O
errors	O
made	O
in	O
interpreting	O
and	O
extracting	O
users	O
 '	O
requirements	O
,	O
planning	O
a	O
program	O
's	O
design	B-Architecture
,	O
writing	O
its	O
source	O
code	O
,	O
and	O
from	O
interaction	O
with	O
humans	O
,	O
hardware	O
and	O
programs	O
,	O
such	O
as	O
operating	B-General_Concept
systems	I-General_Concept
or	O
libraries	B-Library
.	O
</s>
<s>
A	O
program	O
with	O
many	O
,	O
or	O
serious	O
,	O
bugs	B-Error_Name
is	O
often	O
described	O
as	O
buggy	O
.	O
</s>
<s>
Bugs	B-Error_Name
can	O
trigger	O
errors	O
that	O
may	O
have	O
ripple	O
effects	O
.	O
</s>
<s>
The	O
effects	O
of	O
bugs	B-Error_Name
may	O
be	O
subtle	O
,	O
such	O
as	O
unintended	O
text	O
formatting	O
,	O
through	O
to	O
more	O
obvious	O
effects	O
such	O
as	O
causing	O
a	O
program	O
to	O
crash	B-General_Concept
,	O
freezing	B-General_Concept
the	O
computer	O
,	O
or	O
causing	O
damage	O
to	O
hardware	O
.	O
</s>
<s>
Other	O
bugs	B-Error_Name
qualify	O
as	O
security	O
bugs	B-Error_Name
and	O
might	O
,	O
for	O
example	O
,	O
enable	O
a	O
malicious	O
user	O
to	O
bypass	O
access	O
controls	O
in	O
order	O
to	O
obtain	O
unauthorized	O
privileges	O
.	O
</s>
<s>
Some	O
software	B-Error_Name
bugs	I-Error_Name
have	O
been	O
linked	O
to	O
disasters	O
.	O
</s>
<s>
Bugs	B-Error_Name
in	O
code	O
that	O
controlled	O
the	O
Therac-25	O
radiation	O
therapy	O
machine	O
were	O
directly	O
responsible	O
for	O
patient	O
deaths	O
in	O
the	O
1980s	O
.	O
</s>
<s>
In	O
1996	O
,	O
the	O
European	O
Space	O
Agency	O
's	O
US$1billion	O
prototype	O
Ariane	B-Language
5	I-Language
rocket	I-Language
was	I-Language
destroyed	I-Language
less	O
than	O
a	O
minute	O
after	O
launch	O
due	O
to	O
a	O
bug	B-Error_Name
in	O
the	O
on-board	O
guidance	O
computer	O
program	O
.	O
</s>
<s>
In	O
1994	O
,	O
an	O
RAF	O
Chinook	O
helicopter	O
crashed	O
,	O
killing	O
29	O
;	O
this	O
was	O
initially	O
blamed	O
on	O
pilot	O
error	O
,	O
but	O
was	O
later	O
thought	O
to	O
have	O
been	O
caused	O
by	O
a	O
software	B-Error_Name
bug	I-Error_Name
in	O
the	O
engine-control	O
computer	O
.	O
</s>
<s>
Buggy	O
software	O
caused	O
the	O
early	O
21st	O
century	O
British	B-Architecture
Post	I-Architecture
Office	I-Architecture
scandal	I-Architecture
,	O
the	O
most	O
widespread	O
miscarriage	O
of	O
justice	O
in	O
British	O
legal	O
history	O
.	O
</s>
<s>
In	O
2002	O
,	O
a	O
study	O
commissioned	O
by	O
the	O
US	O
Department	O
of	O
Commerce	O
's	O
National	O
Institute	O
of	O
Standards	O
and	O
Technology	O
concluded	O
that	O
"	O
software	B-Error_Name
bugs	I-Error_Name
,	O
or	O
errors	O
,	O
are	O
so	O
prevalent	O
and	O
so	O
detrimental	O
that	O
they	O
cost	O
the	O
US	O
economy	O
an	O
estimated	O
$59billion	O
annually	O
,	O
or	O
about	O
0.6	O
percent	O
of	O
the	O
gross	O
domestic	O
product	O
"	O
.	O
</s>
<s>
The	O
term	O
"	O
bug	B-Error_Name
"	O
to	O
describe	O
defects	O
has	O
been	O
a	O
part	O
of	O
engineering	O
jargon	O
since	O
the	O
1870s	O
and	O
predates	O
electronics	O
and	O
computers	O
;	O
it	O
may	O
have	O
originally	O
been	O
used	O
in	O
hardware	O
engineering	O
to	O
describe	O
mechanical	O
malfunctions	O
.	O
</s>
<s>
Baffle	O
Ball	O
,	O
the	O
first	O
mechanical	O
pinball	B-Application
game	O
,	O
was	O
advertised	O
as	O
being	O
"	O
free	O
of	O
bugs	B-Error_Name
"	O
in	O
1931	O
.	O
</s>
<s>
Problems	O
with	O
military	O
gear	O
during	O
World	O
War	O
II	O
were	O
referred	O
to	O
as	O
bugs	B-Error_Name
(	O
or	O
glitches	B-Error_Name
)	O
.	O
</s>
<s>
In	O
a	O
book	O
published	O
in	O
1942	O
,	O
Louise	O
Dickinson	O
Rich	O
,	O
speaking	O
of	O
a	O
powered	O
ice	O
cutting	O
machine	O
,	O
said	O
,	O
"	O
Ice	O
sawing	O
was	O
suspended	O
until	O
the	O
creator	O
could	O
be	O
brought	O
in	O
to	O
take	O
the	O
bugs	B-Error_Name
out	O
of	O
his	O
darling.	O
"	O
</s>
<s>
Isaac	O
Asimov	O
used	O
the	O
term	O
"	O
bug	B-Error_Name
"	O
to	O
relate	O
to	O
issues	O
with	O
a	O
robot	O
in	O
his	O
short	O
story	O
"	O
Catch	O
That	O
Rabbit	O
"	O
,	O
published	O
in	O
1944	O
.	O
</s>
<s>
The	O
term	O
"	O
bug	B-Error_Name
"	O
was	O
used	O
in	O
an	O
account	O
by	O
computer	O
pioneer	O
Grace	O
Hopper	O
,	O
who	O
publicized	O
the	O
cause	O
of	O
a	O
malfunction	O
in	O
an	O
early	O
electromechanical	O
computer	O
.	O
</s>
<s>
Hopper	O
was	O
not	O
present	O
when	O
the	O
bug	B-Error_Name
was	O
found	O
,	O
but	O
it	O
became	O
one	O
of	O
her	O
favorite	O
stories	O
.	O
</s>
<s>
The	O
operators	O
who	O
found	O
it	O
,	O
including	O
William	O
"	O
Bill	O
"	O
Burke	O
,	O
later	O
of	O
the	O
Naval	O
Weapons	O
Laboratory	O
,	O
Dahlgren	O
,	O
Virginia	O
,	O
were	O
familiar	O
with	O
the	O
engineering	O
term	O
and	O
amusedly	O
kept	O
the	O
insect	O
with	O
the	O
notation	O
"	O
First	O
actual	O
case	O
of	O
bug	B-Error_Name
being	O
found.	O
"	O
</s>
<s>
The	O
related	O
term	O
"	O
debug	B-Device
"	O
also	O
appears	O
to	O
predate	O
its	O
usage	O
in	O
computing	O
:	O
the	O
Oxford	O
English	O
Dictionarys	O
etymology	O
of	O
the	O
word	O
contains	O
an	O
attestation	O
from	O
1945	O
,	O
in	O
the	O
context	O
of	O
aircraft	O
engines	O
.	O
</s>
<s>
The	O
concept	O
that	O
software	O
might	O
contain	O
errors	O
dates	O
back	O
to	O
Ada	O
Lovelace	O
's	O
1843	O
notes	O
on	O
the	B-Device
analytical	I-Device
engine	I-Device
,	O
in	O
which	O
she	O
speaks	O
of	O
the	O
possibility	O
of	O
program	O
"	O
cards	O
"	O
for	O
Charles	O
Babbage	O
's	O
analytical	B-Device
engine	I-Device
being	O
erroneous	O
:	O
</s>
<s>
The	O
Open	O
Technology	O
Institute	O
,	O
run	O
by	O
the	O
group	O
,	O
New	O
America	O
,	O
released	O
a	O
report	O
"	O
Bugs	B-Error_Name
in	O
the	O
System	O
"	O
in	O
August	O
2016	O
stating	O
that	O
U.S.	O
policymakers	O
should	O
make	O
reforms	O
to	O
help	O
researchers	O
identify	O
and	O
address	O
software	B-Error_Name
bugs	I-Error_Name
.	O
</s>
<s>
While	O
the	O
use	O
of	O
the	O
term	O
"	O
bug	B-Error_Name
"	O
to	O
describe	O
software	B-Error_Name
errors	I-Error_Name
is	O
common	O
,	O
many	O
have	O
suggested	O
that	O
it	O
should	O
be	O
abandoned	O
.	O
</s>
<s>
One	O
argument	O
is	O
that	O
the	O
word	O
"	O
bug	B-Error_Name
"	O
is	O
divorced	O
from	O
a	O
sense	O
that	O
a	O
human	O
being	O
caused	O
the	O
problem	O
,	O
and	O
instead	O
implies	O
that	O
the	O
defect	O
arose	O
on	O
its	O
own	O
,	O
leading	O
to	O
a	O
push	O
to	O
abandon	O
the	O
term	O
"	O
bug	B-Error_Name
"	O
in	O
favor	O
of	O
terms	O
such	O
as	O
"	O
defect	O
"	O
,	O
with	O
limited	O
success	O
.	O
</s>
<s>
Since	O
the	O
1970s	O
Gary	O
Kildall	O
somewhat	O
humorously	O
suggested	O
to	O
use	O
the	O
term	O
"	O
blunder	B-Error_Name
"	O
.	O
</s>
<s>
In	O
software	B-General_Concept
engineering	I-General_Concept
,	O
mistake	O
metamorphism	O
(	O
from	O
Greek	O
meta	O
=	O
"	O
change	O
"	O
,	O
morph	O
=	O
"	O
form	O
"	O
)	O
refers	O
to	O
the	O
evolution	O
of	O
a	O
defect	O
in	O
the	O
final	O
stage	O
of	O
software	O
deployment	O
.	O
</s>
<s>
Transformation	O
of	O
a	O
"	O
mistake	O
"	O
committed	O
by	O
an	O
analyst	O
in	O
the	O
early	O
stages	O
of	O
the	B-Application
software	I-Application
development	O
lifecycle	O
,	O
which	O
leads	O
to	O
a	O
"	O
defect	O
"	O
in	O
the	O
final	O
stage	O
of	O
the	O
cycle	O
has	O
been	O
called	O
'	O
mistake	O
metamorphism	O
 '	O
.	O
</s>
<s>
Different	O
stages	O
of	O
a	O
"	O
mistake	O
"	O
in	O
the	O
entire	O
cycle	O
may	O
be	O
described	O
as	O
"	O
mistakes	O
"	O
,	O
"	O
anomalies	O
"	O
,	O
"	O
faults	O
"	O
,	O
"	O
failures	O
"	O
,	O
"	O
errors	O
"	O
,	O
"	O
exceptions	O
"	O
,	O
"	O
crashes	B-General_Concept
"	O
,	O
"	O
glitches	B-Error_Name
"	O
,	O
"	O
bugs	B-Error_Name
"	O
,	O
"	O
defects	O
"	O
,	O
"	O
incidents	O
"	O
,	O
or	O
"	O
side	O
effects	O
"	O
.	O
</s>
<s>
The	B-Application
software	I-Application
industry	O
has	O
put	O
much	O
effort	O
into	O
reducing	O
bug	B-Error_Name
counts	O
.	O
</s>
<s>
Bugs	B-Error_Name
usually	O
appear	O
when	O
the	O
programmer	O
makes	O
a	O
logic	B-General_Concept
error	I-General_Concept
.	O
</s>
<s>
Various	O
innovations	O
in	O
programming	B-Language
style	I-Language
and	O
defensive	B-Application
programming	I-Application
are	O
designed	O
to	O
make	O
these	O
bugs	B-Error_Name
less	O
likely	O
,	O
or	O
easier	O
to	O
spot	O
.	O
</s>
<s>
Several	O
schemes	O
assist	O
managing	O
programmer	O
activity	O
so	O
that	O
fewer	O
bugs	B-Error_Name
are	O
produced	O
.	O
</s>
<s>
Software	B-General_Concept
engineering	I-General_Concept
(	O
which	O
addresses	O
software	O
design	B-Architecture
issues	O
as	O
well	O
)	O
applies	O
many	O
techniques	O
to	O
prevent	O
defects	O
.	O
</s>
<s>
For	O
example	O
,	O
formal	O
program	B-Application
specifications	I-Application
state	O
the	O
exact	O
behavior	O
of	O
programs	O
so	O
that	O
design	B-Architecture
bugs	B-Error_Name
may	O
be	O
eliminated	O
.	O
</s>
<s>
Unfortunately	O
,	O
formal	B-Application
specifications	I-Application
are	O
impractical	O
for	O
anything	O
but	O
the	O
shortest	O
programs	O
,	O
because	O
of	O
problems	O
of	O
combinatorial	O
explosion	O
and	O
indeterminacy	O
.	O
</s>
<s>
A	O
school	O
of	O
thought	O
popularized	O
by	O
Eric	O
S	O
.	O
Raymond	O
as	O
Linus	B-Application
's	I-Application
law	I-Application
says	O
that	O
popular	O
open-source	B-Application
software	I-Application
has	O
more	O
chance	O
of	O
having	O
few	O
or	O
no	O
bugs	B-Error_Name
than	O
other	O
software	O
,	O
because	O
"	O
given	B-Application
enough	I-Application
eyeballs	I-Application
,	O
all	O
bugs	B-Error_Name
are	O
shallow	O
"	O
.	O
</s>
<s>
An	O
example	O
of	O
an	O
open-source	B-Application
software	I-Application
bug	B-Error_Name
was	O
the	O
2008	O
OpenSSL	O
vulnerability	O
in	O
Debian	O
.	O
</s>
<s>
Programming	O
languages	O
include	O
features	O
to	O
help	O
prevent	O
bugs	B-Error_Name
,	O
such	O
as	O
static	O
type	O
systems	O
,	O
restricted	O
namespaces	O
and	O
modular	B-Architecture
programming	I-Architecture
.	O
</s>
<s>
For	O
example	O
,	O
when	O
a	O
programmer	O
writes	O
(	O
pseudocode	B-Language
)	O
LET	O
REAL_VALUE	O
PI	O
=	O
"	O
THREE	O
AND	O
A	O
BIT	O
"	O
,	O
although	O
this	O
may	O
be	O
syntactically	O
correct	O
,	O
the	O
code	O
fails	O
a	O
type	O
check	O
.	O
</s>
<s>
Some	O
languages	O
deliberately	O
exclude	O
features	O
that	O
easily	O
lead	O
to	O
bugs	B-Error_Name
,	O
at	O
the	O
expense	O
of	O
slower	O
performance	O
:	O
the	O
general	O
principle	O
being	O
that	O
,	O
it	O
is	O
almost	O
always	O
better	O
to	O
write	O
simpler	O
,	O
slower	O
code	O
than	O
inscrutable	O
code	O
that	O
runs	O
slightly	O
faster	O
,	O
especially	O
considering	O
that	O
maintenance	O
cost	O
is	O
substantial	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
Java	B-Language
programming	I-Language
language	I-Language
does	O
not	O
support	O
pointer	O
arithmetic	O
;	O
implementations	O
of	O
some	O
languages	O
such	O
as	O
Pascal	B-Application
and	O
scripting	B-Language
languages	I-Language
often	O
have	O
runtime	O
bounds	B-Data_Structure
checking	I-Data_Structure
of	O
arrays	O
,	O
at	O
least	O
in	O
a	O
debugging	O
build	O
.	O
</s>
<s>
Although	O
in	O
general	O
the	O
problem	O
of	O
finding	O
all	O
programming	B-Error_Name
errors	I-Error_Name
given	O
a	O
specification	B-Application
is	O
not	O
solvable	O
(	O
see	O
halting	O
problem	O
)	O
,	O
these	O
tools	O
exploit	O
the	O
fact	O
that	O
human	O
programmers	O
tend	O
to	O
make	O
certain	O
kinds	O
of	O
simple	O
mistakes	O
often	O
when	O
writing	O
software	B-Application
.	I-Application
</s>
<s>
Tools	O
to	O
monitor	O
the	O
performance	O
of	O
the	B-Application
software	I-Application
as	O
it	O
is	O
running	O
,	O
either	O
specifically	O
to	O
find	O
problems	O
such	O
as	O
bottlenecks	O
or	O
to	O
give	O
assurance	O
as	O
to	O
correct	O
working	O
,	O
may	O
be	O
embedded	O
in	O
the	O
code	O
explicitly	O
(	O
perhaps	O
as	O
simple	O
as	O
a	O
statement	O
saying	O
PRINT	O
"	O
I	O
AM	O
HERE	O
"	O
)	O
,	O
or	O
provided	O
as	O
tools	O
.	O
</s>
<s>
Software	O
testers	O
are	O
people	O
whose	O
primary	O
task	O
is	O
to	O
find	O
bugs	B-Error_Name
,	O
or	O
write	O
code	O
to	O
support	O
testing	O
.	O
</s>
<s>
Measurements	O
during	O
testing	O
can	O
provide	O
an	O
estimate	O
of	O
the	O
number	O
of	O
likely	O
bugs	B-Error_Name
remaining	O
;	O
this	O
becomes	O
more	O
reliable	O
the	O
longer	O
a	O
product	O
is	O
tested	O
and	O
developed	O
.	O
</s>
<s>
Finding	O
and	O
fixing	O
bugs	B-Error_Name
,	O
or	O
debugging	O
,	O
is	O
a	O
major	O
part	O
of	O
computer	B-General_Concept
programming	I-General_Concept
.	O
</s>
<s>
Usually	O
,	O
the	O
most	O
difficult	O
part	O
of	O
debugging	O
is	O
finding	O
the	O
bug	B-Error_Name
.	O
</s>
<s>
Programs	O
known	O
as	O
debuggers	B-Application
help	O
programmers	O
locate	O
bugs	B-Error_Name
by	O
executing	O
code	O
line	O
by	O
line	O
,	O
watching	O
variable	O
values	O
,	O
and	O
other	O
features	O
to	O
observe	O
program	O
behavior	O
.	O
</s>
<s>
Without	O
a	O
debugger	B-Application
,	O
code	O
may	O
be	O
added	O
so	O
that	O
messages	O
or	O
values	O
may	O
be	O
written	O
to	O
a	O
console	O
or	O
to	O
a	O
window	O
or	O
log	O
file	O
to	O
trace	O
program	O
execution	O
or	O
show	O
values	O
.	O
</s>
<s>
However	O
,	O
even	O
with	O
the	O
aid	O
of	O
a	O
debugger	B-Application
,	O
locating	O
bugs	B-Error_Name
is	O
something	O
of	O
an	O
art	O
.	O
</s>
<s>
It	O
is	O
not	O
uncommon	O
for	O
a	O
bug	B-Error_Name
in	O
one	O
section	O
of	O
a	O
program	O
to	O
cause	O
failures	O
in	O
a	O
completely	O
different	O
section	O
,	O
thus	O
making	O
it	O
especially	O
difficult	O
to	O
track	O
(	O
for	O
example	O
,	O
an	O
error	O
in	O
a	O
graphics	O
rendering	O
routine	O
causing	O
a	O
file	O
I/O	B-General_Concept
routine	O
to	O
fail	O
)	O
,	O
in	O
an	O
apparently	O
unrelated	O
part	O
of	O
the	O
system	O
.	O
</s>
<s>
Sometimes	O
,	O
a	O
bug	B-Error_Name
is	O
not	O
an	O
isolated	O
flaw	O
,	O
but	O
represents	O
an	O
error	O
of	O
thinking	O
or	O
planning	O
on	O
the	O
part	O
of	O
the	O
programmer	O
.	O
</s>
<s>
Such	O
logic	B-General_Concept
errors	I-General_Concept
require	O
a	O
section	O
of	O
the	O
program	O
to	O
be	O
overhauled	O
or	O
rewritten	O
.	O
</s>
<s>
As	O
a	O
part	O
of	O
code	O
review	O
,	O
stepping	O
through	O
the	O
code	O
and	O
imagining	O
or	O
transcribing	O
the	O
execution	O
process	O
may	O
often	O
find	O
errors	O
without	O
ever	O
reproducing	O
the	O
bug	B-Error_Name
as	O
such	O
.	O
</s>
<s>
More	O
typically	O
,	O
the	O
first	O
step	O
in	O
locating	O
a	O
bug	B-Error_Name
is	O
to	O
reproduce	O
it	O
reliably	O
.	O
</s>
<s>
Once	O
the	O
bug	B-Error_Name
is	O
reproducible	O
,	O
the	O
programmer	O
may	O
use	O
a	O
debugger	B-Application
or	O
other	O
tool	O
while	O
reproducing	O
the	O
error	O
to	O
find	O
the	O
point	O
at	O
which	O
the	O
program	O
went	O
astray	O
.	O
</s>
<s>
Some	O
bugs	B-Error_Name
are	O
revealed	O
by	O
inputs	O
that	O
may	O
be	O
difficult	O
for	O
the	O
programmer	O
to	O
re-create	O
.	O
</s>
<s>
One	O
cause	O
of	O
the	O
Therac-25	O
radiation	O
machine	O
deaths	O
was	O
a	O
bug	B-Error_Name
(	O
specifically	O
,	O
a	O
race	B-Operating_System
condition	I-Operating_System
)	O
that	O
occurred	O
only	O
when	O
the	O
machine	O
operator	O
very	O
rapidly	O
entered	O
a	O
treatment	O
plan	O
;	O
it	O
took	O
days	O
of	O
practice	O
to	O
become	O
able	O
to	O
do	O
this	O
,	O
so	O
the	O
bug	B-Error_Name
did	O
not	O
manifest	O
in	O
testing	O
or	O
when	O
the	O
manufacturer	O
attempted	O
to	O
duplicate	O
it	O
.	O
</s>
<s>
Other	O
bugs	B-Error_Name
may	O
stop	O
occurring	O
whenever	O
the	O
setup	O
is	O
augmented	O
to	O
help	O
find	O
the	O
bug	B-Error_Name
,	O
such	O
as	O
running	O
the	O
program	O
with	O
a	O
debugger	B-Application
;	O
these	O
are	O
called	O
heisenbugs	O
(	O
humorously	O
named	O
after	O
the	O
Heisenberg	O
uncertainty	O
principle	O
)	O
.	O
</s>
<s>
Since	O
the	O
1990s	O
,	O
particularly	O
following	O
the	O
Ariane	B-Language
5	I-Language
Flight	I-Language
501	I-Language
disaster	O
,	O
interest	O
in	O
automated	O
aids	O
to	O
debugging	O
rose	O
,	O
such	O
as	O
static	O
code	O
analysis	O
by	O
abstract	O
interpretation	O
.	O
</s>
<s>
Some	O
classes	O
of	O
bugs	B-Error_Name
have	O
nothing	O
to	O
do	O
with	O
the	O
code	O
.	O
</s>
<s>
Embedded	B-Architecture
systems	I-Architecture
frequently	O
work	B-Application
around	I-Application
hardware	B-Error_Name
bugs	I-Error_Name
,	O
since	O
to	O
make	O
a	O
new	O
version	O
of	O
a	O
ROM	B-Device
is	O
much	O
cheaper	O
than	O
remanufacturing	O
the	O
hardware	O
,	O
especially	O
if	O
they	O
are	O
commodity	O
items	O
.	O
</s>
<s>
To	O
facilitate	O
reproducible	O
research	O
on	O
testing	O
and	O
debugging	O
,	O
researchers	O
use	O
curated	O
benchmarks	O
of	O
bugs	B-Error_Name
:	O
</s>
<s>
ManyBugs	O
is	O
a	O
benchmark	O
of	O
185	O
C	O
bugs	B-Error_Name
in	O
nine	O
open-source	B-Application
programs	I-Application
.	O
</s>
<s>
Defects4J	O
is	O
a	O
benchmark	O
of	O
341	O
Java	B-Language
bugs	B-Error_Name
from	O
5	O
open-source	B-Application
projects	O
.	O
</s>
<s>
Bug	B-Error_Name
management	O
includes	O
the	O
process	O
of	O
documenting	O
,	O
categorizing	O
,	O
assigning	O
,	O
reproducing	O
,	O
correcting	O
and	O
releasing	O
the	O
corrected	O
code	O
.	O
</s>
<s>
Proposed	O
changes	O
to	O
software	O
–	O
bugs	B-Error_Name
as	O
well	O
as	O
enhancement	O
requests	O
and	O
even	O
entire	O
releases	O
–	O
are	O
commonly	O
tracked	O
and	O
managed	O
using	O
bug	B-Application
tracking	I-Application
systems	I-Application
or	O
issue	B-Application
tracking	I-Application
systems	I-Application
.	O
</s>
<s>
The	O
items	O
added	O
may	O
be	O
called	O
defects	O
,	O
tickets	B-Application
,	O
issues	O
,	O
or	O
,	O
following	O
the	O
agile	O
development	O
paradigm	O
,	O
stories	O
and	O
epics	O
.	O
</s>
<s>
Categories	O
may	O
be	O
objective	O
,	O
subjective	O
or	O
a	O
combination	O
,	O
such	O
as	O
version	O
number	O
,	O
area	O
of	O
the	B-Application
software	I-Application
,	O
severity	O
and	O
priority	O
,	O
as	O
well	O
as	O
what	O
type	O
of	O
issue	O
it	O
is	O
,	O
such	O
as	O
a	O
feature	O
request	O
or	O
a	O
bug	B-Error_Name
.	O
</s>
<s>
A	O
bug	B-Error_Name
triage	O
reviews	O
bugs	B-Error_Name
and	O
decides	O
whether	O
and	O
when	O
to	O
fix	O
them	O
.	O
</s>
<s>
The	O
decision	O
is	O
based	O
on	O
the	O
bug	B-Error_Name
's	O
priority	O
,	O
and	O
factors	O
such	O
as	O
project	O
schedules	O
.	O
</s>
<s>
The	O
triage	O
is	O
not	O
meant	O
to	O
investigate	O
the	O
cause	O
of	O
bugs	B-Error_Name
,	O
but	O
rather	O
the	O
cost	O
of	O
fixing	O
them	O
.	O
</s>
<s>
The	O
triage	O
happens	O
regularly	O
,	O
and	O
goes	O
through	O
bugs	B-Error_Name
opened	O
or	O
reopened	O
since	O
the	O
previous	O
meeting	O
.	O
</s>
<s>
Severity	O
is	O
the	O
intensity	O
of	O
the	O
impact	O
the	O
bug	B-Error_Name
has	O
on	O
system	O
operation	O
.	O
</s>
<s>
A	O
crash	B-General_Concept
in	O
a	O
video	O
game	O
has	O
a	O
totally	O
different	O
impact	O
than	O
a	O
crash	B-General_Concept
in	O
a	O
web	O
browser	O
,	O
or	O
real	O
time	O
monitoring	O
system	O
.	O
</s>
<s>
For	O
example	O
,	O
bug	B-Error_Name
severity	O
levels	O
might	O
be	O
"	O
crash	B-General_Concept
or	O
hang	O
"	O
,	O
"	O
no	O
workaround	B-Application
"	O
(	O
meaning	O
there	O
is	O
no	O
way	O
the	O
customer	O
can	O
accomplish	O
a	O
given	O
task	O
)	O
,	O
"	O
has	O
workaround	B-Application
"	O
(	O
meaning	O
the	O
user	O
can	O
still	O
accomplish	O
the	O
task	O
)	O
,	O
"	O
visual	O
defect	O
"	O
(	O
for	O
example	O
,	O
a	O
missing	O
image	O
or	O
displaced	O
button	O
or	O
form	O
element	O
)	O
,	O
or	O
"	O
documentation	O
error	O
"	O
.	O
</s>
<s>
The	O
severity	O
of	O
a	O
bug	B-Error_Name
may	O
be	O
a	O
separate	O
category	O
to	O
its	O
priority	O
for	O
fixing	O
,	O
and	O
the	O
two	O
may	O
be	O
quantified	O
and	O
managed	O
separately	O
.	O
</s>
<s>
Priority	O
controls	O
where	O
a	O
bug	B-Error_Name
falls	O
on	O
the	O
list	O
of	O
planned	O
changes	O
.	O
</s>
<s>
These	O
rating	O
scales	O
may	O
be	O
similar	O
or	O
even	O
identical	O
to	O
severity	O
ratings	O
,	O
but	O
are	O
evaluated	O
as	O
a	O
combination	O
of	O
the	O
bug	B-Error_Name
's	O
severity	O
with	O
its	O
estimated	O
effort	O
to	O
fix	O
;	O
a	O
bug	B-Error_Name
with	O
low	O
severity	O
but	O
easy	O
to	O
fix	O
may	O
get	O
a	O
higher	O
priority	O
than	O
a	O
bug	B-Error_Name
with	O
moderate	O
severity	O
that	O
requires	O
excessive	O
effort	O
to	O
fix	O
.	O
</s>
<s>
Priority	O
ratings	O
may	O
be	O
aligned	O
with	O
product	O
releases	O
,	O
such	O
as	O
"	O
critical	O
"	O
priority	O
indicating	O
all	O
the	O
bugs	B-Error_Name
that	O
must	O
be	O
fixed	O
before	O
the	O
next	O
software	O
release	O
.	O
</s>
<s>
A	O
bug	B-Error_Name
severe	O
enough	O
to	O
delay	O
or	O
halt	O
the	O
release	O
of	O
the	O
product	O
is	O
called	O
a	O
"	O
show	O
stopper	O
"	O
or	O
"	O
showstopper	O
bug	B-Error_Name
"	O
.	O
</s>
<s>
It	O
is	O
common	O
practice	O
to	O
release	O
software	O
with	O
known	O
,	O
low-priority	O
bugs	B-Error_Name
.	O
</s>
<s>
Bugs	B-Error_Name
of	O
sufficiently	O
high	O
priority	O
may	O
warrant	O
a	O
special	O
release	O
of	O
part	O
of	O
the	O
code	O
containing	O
only	O
modules	B-Architecture
with	O
those	O
fixes	O
.	O
</s>
<s>
Most	O
releases	O
include	O
a	O
mixture	O
of	O
behavior	O
changes	O
and	O
multiple	O
bug	B-Error_Name
fixes	O
.	O
</s>
<s>
Releases	O
that	O
emphasize	O
bug	B-Error_Name
fixes	O
are	O
known	O
as	O
maintenance	O
releases	O
,	O
to	O
differentiate	O
it	O
from	O
major	O
releases	O
that	O
emphasize	O
feature	O
additions	O
or	O
changes	O
.	O
</s>
<s>
Reasons	O
that	O
a	O
software	O
publisher	O
opts	O
not	O
to	O
patch	O
or	O
even	O
fix	O
a	O
particular	O
bug	B-Error_Name
include	O
:	O
</s>
<s>
A	O
deadline	O
must	O
be	O
met	O
and	O
resources	O
are	O
insufficient	O
to	O
fix	O
all	O
bugs	B-Error_Name
by	O
the	O
deadline	O
.	O
</s>
<s>
The	O
bug	B-Error_Name
is	O
already	O
fixed	O
in	O
an	O
upcoming	O
release	O
,	O
and	O
it	O
is	O
not	O
of	O
high	O
priority	O
.	O
</s>
<s>
The	O
changes	O
required	O
to	O
fix	O
the	O
bug	B-Error_Name
are	O
too	O
costly	O
or	O
affect	O
too	O
many	O
other	O
components	O
,	O
requiring	O
a	O
major	O
testing	O
activity	O
.	O
</s>
<s>
"	O
It	O
's	O
not	O
a	O
bug	B-Error_Name
,	O
it	O
's	O
a	O
feature	O
"	O
.	O
</s>
<s>
A	O
misunderstanding	O
has	O
arisen	O
between	O
expected	O
and	O
perceived	O
behavior	O
or	O
undocumented	B-General_Concept
feature	I-General_Concept
.	O
</s>
<s>
Bugs	B-Error_Name
arise	O
from	O
oversight	O
or	O
misunderstanding	O
by	O
a	O
software	O
team	O
during	O
specification	B-Application
,	O
design	B-Architecture
,	O
coding	O
,	O
configuration	O
,	O
data	O
entry	O
or	O
documentation	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
relatively	O
simple	O
program	O
to	O
alphabetize	O
a	O
list	O
of	O
words	O
,	O
the	O
design	B-Architecture
might	O
fail	O
to	O
consider	O
what	O
should	O
happen	O
when	O
a	O
word	O
contains	O
a	O
hyphen	O
.	O
</s>
<s>
Or	O
when	O
converting	O
an	O
abstract	O
design	B-Architecture
into	O
code	O
,	O
the	O
coder	O
might	O
inadvertently	O
create	O
an	O
off-by-one	B-Error_Name
error	I-Error_Name
which	O
can	O
be	O
a	O
"	O
<	O
"	O
where	O
"	O
<=	O
"	O
was	O
intended	O
,	O
and	O
fail	O
to	O
sort	O
the	O
last	O
word	O
in	O
a	O
list	O
.	O
</s>
<s>
Another	O
category	O
of	O
bug	B-Error_Name
is	O
called	O
a	O
race	B-Operating_System
condition	I-Operating_System
that	O
may	O
occur	O
when	O
programs	O
have	O
multiple	O
components	O
executing	O
at	O
the	O
same	O
time	O
.	O
</s>
<s>
These	O
bugs	B-Error_Name
may	O
be	O
difficult	O
to	O
detect	O
or	O
anticipate	O
,	O
since	O
they	O
may	O
not	O
occur	O
during	O
every	O
execution	O
of	O
a	O
program	O
.	O
</s>
<s>
Conceptual	O
errors	O
are	O
a	O
developer	O
's	O
misunderstanding	O
of	O
what	O
the	B-Application
software	I-Application
must	O
do	O
.	O
</s>
<s>
These	O
can	O
be	O
from	O
a	O
lack	O
of	O
awareness	O
of	O
the	O
qualities	O
of	O
the	O
data	O
storage	O
such	O
as	O
a	O
loss	B-Architecture
of	I-Architecture
precision	I-Architecture
due	O
to	O
rounding	B-Algorithm
,	O
numerically	B-Algorithm
unstable	I-Algorithm
algorithms	O
,	O
arithmetic	B-Algorithm
overflow	I-Algorithm
and	O
underflow	B-Algorithm
,	O
or	O
from	O
lack	O
of	O
awareness	O
of	O
how	O
calculations	O
are	O
handled	O
by	O
different	O
software	O
coding	O
languages	O
such	O
as	O
division	O
by	O
zero	O
which	O
in	O
some	O
languages	O
may	O
throw	O
an	O
exception	O
,	O
and	O
in	O
others	O
may	O
return	O
a	O
special	O
value	O
such	O
as	O
NaN	O
or	O
infinity	O
.	O
</s>
<s>
Control	O
flow	O
bugs	B-Error_Name
are	O
those	O
found	O
in	O
processes	O
with	O
valid	O
logic	O
,	O
but	O
that	O
lead	O
to	O
unintended	O
results	O
,	O
such	O
as	O
infinite	B-Algorithm
loops	I-Algorithm
and	O
infinite	O
recursion	O
,	O
incorrect	O
comparisons	O
for	O
conditional	B-Language
statements	I-Language
such	O
as	O
using	O
the	O
incorrect	O
comparison	O
operator	O
,	O
and	O
off-by-one	B-Error_Name
errors	I-Error_Name
(	O
counting	O
one	O
too	O
many	O
or	O
one	O
too	O
few	O
iterations	O
when	O
looping	O
)	O
.	O
</s>
<s>
Incorrect	O
API	B-General_Concept
usage	O
.	O
</s>
<s>
A	O
new	O
API	B-General_Concept
or	O
communications	O
protocol	O
may	O
seem	O
to	O
work	O
when	O
two	O
systems	O
use	O
different	O
versions	O
,	O
but	O
errors	O
may	O
occur	O
when	O
a	O
function	O
or	O
feature	O
implemented	O
in	O
one	O
version	O
is	O
changed	O
or	O
missing	O
in	O
another	O
.	O
</s>
<s>
Deadlock	B-Operating_System
,	O
where	O
task	O
A	O
cannot	O
continue	O
until	O
task	O
B	O
finishes	O
,	O
but	O
at	O
the	O
same	O
time	O
,	O
task	O
B	O
cannot	O
continue	O
until	O
task	O
A	O
finishes	O
.	O
</s>
<s>
Race	B-Operating_System
condition	I-Operating_System
,	O
where	O
the	O
computer	O
does	O
not	O
perform	O
tasks	O
in	O
the	O
order	O
the	O
programmer	O
intended	O
.	O
</s>
<s>
Concurrency	O
errors	O
in	O
critical	B-Operating_System
sections	I-Operating_System
,	O
mutual	B-Operating_System
exclusions	I-Operating_System
and	O
other	O
features	O
of	O
concurrent	O
processing	O
.	O
</s>
<s>
Time-of-check-to-time-of-use	B-Error_Name
(	O
TOCTOU	B-Error_Name
)	O
is	O
a	O
form	O
of	O
unprotected	O
critical	B-Operating_System
section	I-Operating_System
.	O
</s>
<s>
Using	O
an	O
uninitialized	B-Error_Name
variable	I-Error_Name
.	O
</s>
<s>
Access	B-Error_Name
violations	I-Error_Name
.	O
</s>
<s>
Resource	O
leaks	O
,	O
where	O
a	O
finite	O
system	O
resource	O
(	O
such	O
as	O
memory	B-Error_Name
or	O
file	B-General_Concept
handles	I-General_Concept
)	O
become	O
exhausted	O
by	O
repeated	O
allocation	O
without	O
release	O
.	O
</s>
<s>
Buffer	B-General_Concept
overflow	I-General_Concept
,	O
in	O
which	O
a	O
program	O
tries	O
to	O
store	O
data	O
past	O
the	O
end	O
of	O
allocated	O
storage	O
.	O
</s>
<s>
This	O
may	O
or	O
may	O
not	O
lead	O
to	O
an	O
access	B-Error_Name
violation	I-Error_Name
or	O
storage	B-General_Concept
violation	I-General_Concept
.	O
</s>
<s>
These	O
are	O
frequently	O
security	O
bugs	B-Error_Name
.	O
</s>
<s>
Excessive	O
recursion	O
which	O
—	O
though	O
logically	O
valid	O
—	O
causes	O
stack	B-Error_Name
overflow	I-Error_Name
.	O
</s>
<s>
Use-after-free	O
error	O
,	O
where	O
a	O
pointer	O
is	O
used	O
after	O
the	O
system	O
has	O
freed	O
the	O
memory	B-Error_Name
it	O
references	O
.	O
</s>
<s>
The	O
amount	O
and	O
type	O
of	O
damage	O
a	O
software	B-Error_Name
bug	I-Error_Name
may	O
cause	O
naturally	O
affects	O
decision-making	O
,	O
processes	O
and	O
policy	O
regarding	O
software	O
quality	O
.	O
</s>
<s>
Other	O
than	O
the	O
damage	O
caused	O
by	O
bugs	B-Error_Name
,	O
some	O
of	O
their	O
cost	O
is	O
due	O
to	O
the	O
effort	O
invested	O
in	O
fixing	O
them	O
.	O
</s>
<s>
showed	O
that	O
the	O
median	O
of	O
projects	O
invest	O
17	O
percent	O
of	O
the	O
development	O
effort	O
in	O
bug	B-Error_Name
fixing	O
.	O
</s>
<s>
In	O
2020	O
,	O
research	O
on	O
GitHub	B-Application
repositories	O
showed	O
the	O
median	O
is	O
20%	O
.	O
</s>
<s>
Some	O
projects	O
even	O
attained	O
zero	O
defects	O
:	O
the	O
firmware	B-Application
in	O
the	O
IBM	O
Wheelwriter	O
typewriter	O
which	O
consists	O
of	O
63,000	O
SLOC	O
,	O
and	O
the	O
Space	O
Shuttle	O
software	O
with	O
500,000	O
SLOC	O
.	O
</s>
<s>
A	O
number	O
of	O
software	B-Error_Name
bugs	I-Error_Name
have	O
become	O
well-known	O
,	O
usually	O
due	O
to	O
their	O
severity	O
:	O
examples	O
include	O
various	O
space	O
and	O
military	O
aircraft	O
crashes	B-General_Concept
.	O
</s>
<s>
Possibly	O
the	O
most	O
famous	O
bug	B-Error_Name
is	O
the	O
Year	B-Error_Name
2000	I-Error_Name
problem	I-Error_Name
or	O
Y2K	B-Error_Name
bug	I-Error_Name
,	O
which	O
caused	O
many	O
programs	O
written	O
long	O
before	O
the	O
transition	O
from	O
19xx	O
to	O
20xx	O
dates	O
to	O
malfunction	O
,	O
for	O
example	O
treating	O
a	O
date	O
such	O
as	O
"	O
25	O
Dec	O
04	O
"	O
as	O
being	O
in	O
1904	O
,	O
displaying	O
"	O
19100	B-Error_Name
"	O
instead	O
of	O
"	O
2000	O
"	O
,	O
and	O
so	O
on	O
.	O
</s>
<s>
The	O
2012	O
stock	O
trading	O
disruption	O
involved	O
one	O
such	O
incompatibility	O
between	O
the	O
old	O
API	B-General_Concept
and	O
a	O
new	O
API	B-General_Concept
.	O
</s>
<s>
In	O
both	O
the	O
1968	O
novel	O
2001	O
:	O
A	O
Space	O
Odyssey	O
and	O
the	O
corresponding	O
1968	O
film	O
2001	O
:	O
A	O
Space	O
Odyssey	O
,	O
a	O
spaceship	O
's	O
onboard	O
computer	O
,	O
HAL	B-General_Concept
9000	I-General_Concept
,	O
attempts	O
to	O
kill	O
all	O
its	O
crew	O
members	O
.	O
</s>
<s>
In	O
the	O
English	O
version	O
of	O
the	O
Nena	O
1983	O
song	O
99	O
Luftballons	O
(	O
99	O
Red	O
Balloons	O
)	O
as	O
a	O
result	O
of	O
"	O
bugs	B-Error_Name
in	O
the	B-Application
software	I-Application
"	O
,	O
a	O
release	O
of	O
a	O
group	O
of	O
99	O
red	O
balloons	O
are	O
mistaken	O
for	O
an	O
enemy	O
nuclear	O
missile	O
launch	O
,	O
requiring	O
an	O
equivalent	O
launch	O
response	O
,	O
resulting	O
in	O
catastrophe	O
.	O
</s>
<s>
In	O
the	O
1999	O
American	O
comedy	O
Office	O
Space	O
,	O
three	O
employees	O
attempt	O
(	O
unsuccessfully	O
)	O
to	O
exploit	O
their	O
company	O
's	O
preoccupation	O
with	O
the	O
Y2K	B-Error_Name
computer	I-Error_Name
bug	I-Error_Name
using	O
a	O
computer	O
virus	O
that	O
sends	O
rounded-off	O
fractions	O
of	O
a	O
penny	O
to	O
their	O
bank	O
account	O
—	O
a	O
long-known	O
technique	O
described	O
as	O
salami	O
slicing	O
.	O
</s>
<s>
The	O
2004	O
novel	O
The	O
Bug	B-Error_Name
,	O
by	O
Ellen	O
Ullman	O
,	O
is	O
about	O
a	O
programmer	O
's	O
attempt	O
to	O
find	O
an	O
elusive	O
bug	B-Error_Name
in	O
a	O
database	O
application	O
.	O
</s>
<s>
The	O
2008	O
Canadian	O
film	O
Control	O
Alt	O
Delete	O
is	O
about	O
a	O
computer	O
programmer	O
at	O
the	O
end	O
of	O
1999	O
struggling	O
to	O
fix	O
bugs	B-Error_Name
at	O
his	O
company	O
related	O
to	O
the	O
year	B-Error_Name
2000	I-Error_Name
problem	I-Error_Name
.	O
</s>
