<s>
In	O
software	O
,	O
a	O
spell	B-Application
checker	I-Application
(	O
or	O
spelling	B-Application
checker	I-Application
or	O
spell	B-Application
check	I-Application
)	O
is	O
a	O
software	B-Architecture
feature	I-Architecture
that	O
checks	O
for	O
misspellings	O
in	O
a	O
text	B-General_Concept
.	O
</s>
<s>
Spell-checking	B-Application
features	O
are	O
often	O
embedded	O
in	O
software	O
or	O
services	O
,	O
such	O
as	O
a	O
word	B-General_Concept
processor	I-General_Concept
,	O
email	B-Protocol
client	I-Protocol
,	O
electronic	O
dictionary	B-Operating_System
,	O
or	O
search	B-Application
engine	I-Application
.	O
</s>
<s>
A	O
basic	O
spell	B-Application
checker	I-Application
carries	O
out	O
the	O
following	O
processes	O
:	O
</s>
<s>
It	O
scans	O
the	O
text	B-General_Concept
and	O
extracts	O
the	O
words	O
contained	O
in	O
it	O
.	O
</s>
<s>
a	O
dictionary	B-Operating_System
)	O
.	O
</s>
<s>
Even	O
for	O
a	O
lightly	O
inflected	O
language	O
like	O
English	O
,	O
the	O
spell	B-Application
checker	I-Application
will	O
need	O
to	O
consider	O
different	O
forms	O
of	O
the	O
same	O
word	O
,	O
such	O
as	O
plurals	O
,	O
verbal	O
forms	O
,	O
contractions	O
,	O
and	O
possessives	O
.	O
</s>
<s>
As	O
an	O
adjunct	O
to	O
these	O
components	O
,	O
the	O
program	O
's	O
user	B-Application
interface	I-Application
allows	O
users	O
to	O
approve	O
or	O
reject	O
replacements	O
and	O
modify	O
the	O
program	O
's	O
operation	O
.	O
</s>
<s>
Spell	B-Application
checkers	I-Application
can	O
use	O
approximate	B-Algorithm
string	I-Algorithm
matching	I-Algorithm
algorithms	O
such	O
as	O
Levenshtein	O
distance	O
to	O
find	O
correct	O
spellings	O
of	O
misspelled	O
words	O
.	O
</s>
<s>
An	O
alternative	O
type	O
of	O
spell	B-Application
checker	I-Application
uses	O
solely	O
statistical	O
information	O
,	O
such	O
as	O
n-grams	B-Language
,	O
to	O
recognize	O
errors	O
instead	O
of	O
correctly-spelled	O
words	O
.	O
</s>
<s>
Key	O
advantages	O
include	O
needing	O
less	O
runtime	O
storage	O
and	O
the	O
ability	O
to	O
correct	O
errors	O
in	O
words	O
that	O
are	O
not	O
included	O
in	O
a	O
dictionary	B-Operating_System
.	O
</s>
<s>
In	O
some	O
cases	O
,	O
spell	B-Application
checkers	I-Application
use	O
a	O
fixed	O
list	O
of	O
misspellings	O
and	O
suggestions	B-Application
for	O
those	O
misspellings	O
;	O
this	O
less	O
flexible	O
approach	O
is	O
often	O
used	O
in	O
paper-based	O
correction	O
methods	O
,	O
such	O
as	O
the	O
see	O
also	O
entries	O
of	O
encyclopedias	O
.	O
</s>
<s>
Clustering	B-Algorithm
algorithms	I-Algorithm
have	O
also	O
been	O
used	O
for	O
spell	B-Application
checking	I-Application
combined	O
with	O
phonetic	O
information	O
.	O
</s>
<s>
In	O
1961	O
,	O
Les	O
Earnest	O
,	O
who	O
headed	O
the	O
research	O
on	O
this	O
budding	O
technology	O
,	O
saw	O
it	O
necessary	O
to	O
include	O
the	O
first	O
spell	B-Application
checker	I-Application
that	O
accessed	O
a	O
list	O
of	O
10,000	O
acceptable	O
words	O
.	O
</s>
<s>
Ralph	O
Gorin	O
,	O
a	O
graduate	O
student	O
under	O
Earnest	O
at	O
the	O
time	O
,	O
created	O
the	O
first	O
true	O
spelling	B-Application
checker	I-Application
program	O
written	O
as	O
an	O
applications	O
program	O
(	O
rather	O
than	O
research	O
)	O
for	O
general	O
English	O
text	B-General_Concept
:	O
SPELL	O
for	O
the	O
DEC	O
PDP-10	O
at	O
Stanford	O
University	O
's	O
Artificial	O
Intelligence	O
Laboratory	O
,	O
in	O
February	O
1971	O
.	O
</s>
<s>
Gorin	O
wrote	O
SPELL	O
in	O
assembly	B-Language
language	I-Language
,	O
for	O
faster	O
action	O
;	O
he	O
made	O
the	O
first	O
spelling	O
corrector	O
by	O
searching	O
the	O
word	O
list	O
for	O
plausible	O
correct	O
spellings	O
that	O
differ	O
by	O
a	O
single	O
letter	O
or	O
adjacent	O
letter	O
transpositions	O
and	O
presenting	O
them	O
to	O
the	O
user	O
.	O
</s>
<s>
SPELL	O
,	O
its	O
algorithms	O
and	O
data	O
structures	O
inspired	O
the	O
Unix	O
ispell	B-Application
program	O
.	O
</s>
<s>
The	O
first	O
spell	B-Application
checkers	I-Application
were	O
widely	O
available	O
on	O
mainframe	O
computers	O
in	O
the	O
late	O
1970s	O
.	O
</s>
<s>
A	O
group	O
of	O
six	O
linguists	O
from	O
Georgetown	O
University	O
developed	O
the	O
first	O
spell-check	B-Application
system	O
for	O
the	O
IBM	O
corporation	O
.	O
</s>
<s>
The	O
International	B-Application
Ispell	I-Application
program	O
commonly	O
used	O
in	O
Unix	O
is	O
based	O
on	O
R	O
.	O
E	O
.	O
Gorin	O
's	O
SPELL	O
.	O
</s>
<s>
The	O
GNU	O
project	O
has	O
its	O
spell	B-Application
checker	I-Application
GNU	B-Language
Aspell	I-Language
.	O
</s>
<s>
Aspell	B-Language
's	O
main	O
improvement	O
is	O
that	O
it	O
can	O
more	O
accurately	O
suggest	O
correct	O
alternatives	O
for	O
misspelled	O
English	O
words	O
.	O
</s>
<s>
Due	O
to	O
the	O
inability	O
of	O
traditional	O
spell	B-Application
checkers	I-Application
to	O
check	O
words	O
in	O
complex	O
inflected	O
languages	O
,	O
Hungarian	O
László	O
Németh	O
developed	O
Hunspell	B-Application
,	O
a	O
spell	B-Application
checker	I-Application
that	O
supports	O
agglutinative	O
languages	O
and	O
complex	O
compound	O
words	O
.	O
</s>
<s>
Hunspell	B-Application
also	O
uses	O
Unicode	O
in	O
its	O
dictionaries	B-Operating_System
.	O
</s>
<s>
Hunspell	B-Application
replaced	O
the	O
previous	O
MySpell	B-Application
in	O
OpenOffice.org	B-Application
in	O
version	O
2.0.2	O
.	O
</s>
<s>
Enchant	B-Application
is	O
another	O
general	O
spell	B-Application
checker	I-Application
,	O
derived	O
from	O
AbiWord	B-Language
.	O
</s>
<s>
Its	O
goal	O
is	O
to	O
combine	O
programs	O
supporting	O
different	O
languages	O
such	O
as	O
Aspell	B-Language
,	O
Hunspell	B-Application
,	O
Nuspell	O
,	O
Hspell	O
(	O
Hebrew	O
)	O
,	O
Voikko	O
(	O
Finnish	O
)	O
,	O
Zemberek	O
(	O
Turkish	O
)	O
and	O
AppleSpell	O
under	O
one	O
interface	O
.	O
</s>
<s>
The	O
first	O
spell	B-Application
checkers	I-Application
for	O
personal	O
computers	O
appeared	O
in	O
1980	O
,	O
such	O
as	O
"	O
WordCheck	O
"	O
for	O
Commodore	O
systems	O
which	O
was	O
released	O
in	O
late	O
1980	O
in	O
time	O
for	O
advertisements	O
to	O
go	O
to	O
print	O
in	O
January	O
1981	O
.	O
</s>
<s>
On	O
the	O
pre-Windows	O
PCs	O
,	O
these	O
spell	B-Application
checkers	I-Application
were	O
standalone	O
programs	O
,	O
many	O
of	O
which	O
could	O
be	O
run	O
in	O
terminate-and-stay-resident	O
mode	O
from	O
within	O
word-processing	B-General_Concept
packages	O
on	O
PCs	O
with	O
sufficient	O
memory	O
.	O
</s>
<s>
However	O
,	O
the	O
market	O
for	O
standalone	O
packages	O
was	O
short-lived	O
,	O
as	O
by	O
the	O
mid-1980s	O
developers	O
of	O
popular	O
word-processing	B-General_Concept
packages	O
like	O
WordStar	B-Application
and	O
WordPerfect	B-Application
had	O
incorporated	O
spell	B-Application
checkers	I-Application
in	O
their	O
packages	O
,	O
mostly	O
licensed	O
from	O
the	O
above	O
companies	O
,	O
who	O
quickly	O
expanded	O
support	O
from	O
just	O
English	O
to	O
many	O
European	O
and	O
eventually	O
even	O
Asian	O
languages	O
.	O
</s>
<s>
Although	O
the	O
size	O
of	O
the	O
word-processing	B-General_Concept
market	O
in	O
a	O
country	O
like	O
Iceland	O
might	O
not	O
have	O
justified	O
the	O
investment	O
of	O
implementing	O
a	O
spell	B-Application
checker	I-Application
,	O
companies	O
like	O
WordPerfect	B-Application
nonetheless	O
strove	O
to	O
localize	O
their	O
software	O
for	O
as	O
many	O
national	O
markets	O
as	O
possible	O
as	O
part	O
of	O
their	O
global	O
marketing	O
strategy	O
.	O
</s>
<s>
When	O
Apple	O
developed	O
"	O
a	O
system-wide	O
spelling	B-Application
checker	I-Application
"	O
for	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
so	O
that	O
"	O
the	O
operating	O
system	O
took	O
over	O
spelling	O
fixes	O
,	O
"	O
it	O
was	O
a	O
first	O
:	O
one	O
"	O
did	O
n't	O
have	O
to	O
maintain	O
a	O
separate	O
spelling	B-Application
checker	I-Application
for	O
each	O
"	O
program	O
.	O
</s>
<s>
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
's	O
spellcheck	B-Application
coverage	O
includes	O
virtually	O
all	O
bundled	O
and	O
third	O
party	O
applications	O
.	O
</s>
<s>
It	O
came	O
with	O
a	O
dictionary	B-Operating_System
but	O
had	O
the	O
ability	O
to	O
build	O
and	O
incorporate	O
use	O
of	O
secondary	O
dictionaries	B-Operating_System
.	O
</s>
<s>
Firefox	B-Application
2.0	O
,	O
a	O
web	B-Application
browser	I-Application
,	O
has	O
spell	B-Application
check	I-Application
support	O
for	O
user-written	O
content	O
,	O
such	O
as	O
when	O
editing	O
Wikitext	O
,	O
writing	O
on	O
many	O
webmail	B-Protocol
sites	O
,	O
blogs	O
,	O
and	O
social	O
networking	O
websites	O
.	O
</s>
<s>
The	O
web	B-Application
browsers	I-Application
Google	B-Application
Chrome	I-Application
,	O
Konqueror	B-Application
,	O
and	O
Opera	B-Application
,	O
the	O
email	B-Protocol
client	I-Protocol
Kmail	O
and	O
the	O
instant	B-Application
messaging	I-Application
client	B-Protocol
Pidgin	B-Protocol
also	O
offer	O
spell	B-Application
checking	I-Application
support	O
,	O
transparently	O
using	O
previously	O
GNU	B-Language
Aspell	I-Language
and	O
currently	O
Hunspell	B-Application
as	O
their	O
engine	O
.	O
</s>
<s>
Some	O
spell	B-Application
checkers	I-Application
have	O
separate	O
support	O
for	O
medical	O
dictionaries	B-Operating_System
to	O
help	O
prevent	O
medical	O
errors	O
.	O
</s>
<s>
The	O
first	O
spell	B-Application
checkers	I-Application
were	O
"	O
verifiers	O
"	O
instead	O
of	O
"	O
correctors.	O
"	O
</s>
<s>
They	O
offered	O
no	O
suggestions	B-Application
for	O
incorrectly	O
spelled	O
words	O
.	O
</s>
<s>
The	O
challenge	O
the	O
developers	O
faced	O
was	O
the	O
difficulty	O
in	O
offering	O
useful	O
suggestions	B-Application
for	O
misspelled	O
words	O
.	O
</s>
<s>
It	O
might	O
seem	O
logical	O
that	O
where	O
spell-checking	B-Application
dictionaries	B-Operating_System
are	O
concerned	O
,	O
"	O
the	O
bigger	O
,	O
the	O
better	O
,	O
"	O
so	O
that	O
correct	O
words	O
are	O
not	O
marked	O
as	O
incorrect	O
.	O
</s>
<s>
right|thumb|A	O
screenshot	O
of	O
Enchant	B-Application
,	O
the	O
AbiWord	B-Language
spell	B-Application
checker	I-Application
.	O
</s>
<s>
The	O
first	O
MS-DOS	O
spell	B-Application
checkers	I-Application
were	O
mostly	O
used	O
in	O
proofing	O
mode	O
from	O
within	O
word	O
processing	O
packages	O
.	O
</s>
<s>
After	O
preparing	O
a	O
document	O
,	O
a	O
user	O
scanned	O
the	O
text	B-General_Concept
looking	O
for	O
misspellings	O
.	O
</s>
<s>
Later	O
,	O
however	O
,	O
batch	O
processing	O
was	O
offered	O
in	O
such	O
packages	O
as	O
Oracle	B-Application
's	O
short-lived	O
CoAuthor	O
and	O
allowed	O
a	O
user	O
to	O
view	O
the	O
results	O
after	O
a	O
document	O
was	O
processed	O
and	O
correct	O
only	O
the	O
words	O
that	O
were	O
known	O
to	O
be	O
wrong	O
.	O
</s>
<s>
When	O
memory	O
and	O
processing	O
power	O
became	O
abundant	O
,	O
spell	B-Application
checking	I-Application
was	O
performed	O
in	O
the	O
background	O
in	O
an	O
interactive	O
way	O
,	O
such	O
as	O
has	O
been	O
the	O
case	O
with	O
the	O
Sector	O
Software	O
produced	O
Spellbound	O
program	O
released	O
in	O
1987	O
and	O
Microsoft	B-Application
Word	I-Application
since	O
Word	O
95	O
.	O
</s>
<s>
Spell	B-Application
checkers	I-Application
became	O
increasingly	O
sophisticated	O
;	O
now	O
capable	O
of	O
recognizing	O
grammatical	O
errors	O
.	O
</s>
<s>
However	O
,	O
even	O
at	O
their	O
best	O
,	O
they	O
rarely	O
catch	O
all	O
the	O
errors	O
in	O
a	O
text	B-General_Concept
(	O
such	O
as	O
homophone	O
errors	O
)	O
and	O
will	O
flag	O
neologisms	O
and	O
foreign	O
words	O
as	O
misspellings	O
.	O
</s>
<s>
Nonetheless	O
,	O
spell	B-Application
checkers	I-Application
can	O
be	O
considered	O
as	O
a	O
type	O
of	O
foreign	B-Application
language	I-Application
writing	I-Application
aid	I-Application
that	O
non-native	O
language	O
learners	O
can	O
rely	O
on	O
to	O
detect	O
and	O
correct	O
their	O
misspellings	O
in	O
the	O
target	O
language.Banks	O
,	O
T	O
.	O
(	O
2008	O
)	O
.	O
</s>
<s>
English	O
is	O
unusual	O
in	O
that	O
most	O
words	O
used	O
in	O
formal	O
writing	O
have	O
a	O
single	O
spelling	O
that	O
can	O
be	O
found	O
in	O
a	O
typical	O
dictionary	B-Operating_System
,	O
with	O
the	O
exception	O
of	O
some	O
jargon	O
and	O
modified	O
words	O
.	O
</s>
<s>
Each	O
of	O
these	O
presents	O
unique	O
challenges	O
to	O
non-English	O
language	O
spell	B-Application
checkers	I-Application
.	O
</s>
<s>
Not	O
only	O
does	O
this	O
allow	O
words	O
such	O
as	O
those	O
in	O
the	O
poem	O
above	O
to	O
be	O
caught	O
,	O
but	O
it	O
mitigates	O
the	O
detrimental	O
effect	O
of	O
enlarging	O
dictionaries	B-Operating_System
,	O
allowing	O
more	O
words	O
to	O
be	O
recognized	O
.	O
</s>
<s>
The	O
most	O
successful	O
algorithm	O
to	O
date	O
is	O
Andrew	O
Golding	O
and	O
Dan	O
Roth	O
's	O
"	O
Winnow-based	O
spelling	O
correction	O
algorithm	O
"	O
,	O
published	O
in	O
1999	O
,	O
which	O
is	O
able	O
to	O
recognize	O
about	O
96%	O
of	O
context-sensitive	O
spelling	O
errors	O
,	O
in	O
addition	O
to	O
ordinary	O
non-word	O
spelling	O
errors	O
.	O
</s>
<s>
Context-sensitive	O
spell	B-Application
checkers	I-Application
appeared	O
in	O
the	O
now-defunct	O
applications	O
Microsoft	B-Application
Office	I-Application
2007	I-Application
and	O
Google	B-Application
Wave	I-Application
.	O
</s>
<s>
Grammar	B-Application
checkers	I-Application
attempt	O
to	O
fix	O
problems	O
with	O
grammar	O
beyond	O
spelling	O
errors	O
,	O
including	O
incorrect	O
choice	O
of	O
words	O
.	O
</s>
