<s>
A	O
dead	B-Device
key	I-Device
is	O
a	O
special	O
kind	O
of	O
modifier	B-Device
key	I-Device
on	O
a	O
mechanical	O
typewriter	O
,	O
or	O
computer	B-Device
keyboard	I-Device
,	O
that	O
is	O
typically	O
used	O
to	O
attach	O
a	O
specific	O
diacritic	O
to	O
a	O
base	O
letter	O
.	O
</s>
<s>
The	O
dead	B-Device
key	I-Device
does	O
not	O
generate	O
a	O
(	O
complete	O
)	O
character	O
by	O
itself	O
,	O
but	O
modifies	O
the	O
character	O
generated	O
by	O
the	O
key	O
struck	O
immediately	O
after	O
.	O
</s>
<s>
Thus	O
,	O
a	O
dedicated	O
key	O
is	O
not	O
needed	O
for	O
each	O
possible	O
combination	O
of	O
a	O
diacritic	O
and	O
a	O
letter	O
,	O
but	O
rather	O
only	O
one	O
dead	B-Device
key	I-Device
for	O
each	O
diacritic	O
is	O
needed	O
,	O
in	O
addition	O
to	O
the	O
normal	O
base	O
letter	O
keys	O
.	O
</s>
<s>
For	O
example	O
,	O
if	O
a	O
keyboard	B-Device
has	O
a	O
dead	B-Device
key	I-Device
for	O
the	O
grave	O
accent	O
( `	O
)	O
,	O
the	O
French	O
character	O
à	O
can	O
be	O
generated	O
by	O
first	O
pressing	O
and	O
then	O
,	O
whereas	O
è	O
can	O
be	O
generated	O
by	O
first	O
pressing	O
and	O
then	O
.	O
</s>
<s>
Usually	O
,	O
the	O
diacritic	O
itself	O
can	O
be	O
generated	O
as	O
an	O
isolated	O
character	O
by	O
pressing	O
the	O
dead	B-Device
key	I-Device
followed	O
by	O
space	O
;	O
so	O
a	O
plain	O
grave	O
accent	O
can	O
be	O
typed	O
by	O
pressing	O
and	O
then	O
.	O
</s>
<s>
The	O
dead	B-Device
key	I-Device
is	O
mechanical	O
in	O
origin	O
,	O
and	O
"	O
dead	O
"	O
means	O
without	O
movement	O
.	O
</s>
<s>
Due	O
to	O
a	O
change	O
in	O
the	O
mechanism	O
,	O
striking	O
the	O
key	O
containing	O
the	O
accent	O
did	O
not	O
advance	O
the	O
paper	O
(	O
the	O
key	O
was	O
"	O
dead	O
"	O
or	O
non-spacing	O
)	O
,	O
meaning	O
it	O
could	O
be	O
followed	O
by	O
any	O
character	O
that	O
was	O
to	O
appear	O
under	O
the	O
acute	O
accent	O
,	O
producing	O
an	O
overstruck	B-Application
character	O
.	O
</s>
<s>
Note	O
that	O
with	O
mechanical	O
keyboards	B-Device
,	O
the	O
acute	O
accent	O
could	O
be	O
followed	O
by	O
any	O
character	O
,	O
to	O
create	O
new	O
combinations	O
such	O
as	O
q	O
with	O
acute	O
accent	O
.	O
</s>
<s>
A	O
dead	B-Device
key	I-Device
is	O
different	O
from	O
a	O
typical	O
modifier	B-Device
key	I-Device
(	O
such	O
as	O
or	O
)	O
,	O
in	O
that	O
rather	O
than	O
being	O
pressed	O
and	O
held	O
while	O
another	O
key	O
is	O
struck	O
,	O
the	O
dead	B-Device
key	I-Device
is	O
pressed	O
and	O
released	O
before	O
striking	O
the	O
key	O
to	O
be	O
modified	O
.	O
</s>
<s>
In	O
some	O
computer	O
systems	O
,	O
there	O
is	O
no	O
indication	O
to	O
the	O
user	O
that	O
a	O
dead	B-Device
key	I-Device
has	O
been	O
struck	O
,	O
so	O
the	O
key	O
appears	O
dead	O
(	O
nothing	O
immediately	O
happens	O
)	O
,	O
but	O
in	O
some	O
text-entry	O
systems	O
,	O
the	O
diacritic	O
is	O
displayed	O
,	O
along	O
with	O
an	O
indication	O
that	O
the	O
system	O
is	O
waiting	O
for	O
another	O
keystroke	O
to	O
complete	O
the	O
typing	O
sequence	O
.	O
</s>
<s>
The	O
dead	B-Device
key	I-Device
temporarily	O
changes	O
the	O
mapping	O
of	O
the	O
keyboard	B-Device
for	O
the	O
next	O
keystroke	O
,	O
which	O
activates	O
a	O
special	O
keyboard	B-Device
mode	B-General_Concept
rather	O
than	O
actually	O
generating	O
a	O
modifier	O
character	O
.	O
</s>
<s>
Each	O
combination	O
of	O
a	O
diacritic	O
and	O
a	O
base	O
letter	O
must	O
be	O
specified	O
in	O
the	O
character	B-General_Concept
set	I-General_Concept
and	O
must	O
be	O
supported	O
by	O
the	O
font	O
in	O
use	O
.	O
</s>
<s>
(	O
By	O
using	O
the	O
combining	O
characters	O
available	O
in	O
the	O
Unicode	O
character	B-General_Concept
set	I-General_Concept
,	O
it	O
may	O
be	O
possible	O
to	O
generate	O
a	O
combination	O
that	O
more	O
or	O
less	O
looks	O
like	O
a	O
q	O
with	O
an	O
acute	O
accent	O
(	O
q́	O
)	O
,	O
but	O
that	O
technique	O
is	O
quite	O
distinct	O
from	O
the	O
dead	B-Device
key	I-Device
functionality	O
.	O
</s>
<s>
For	O
convenience	O
,	O
they	O
are	O
generated	O
on	O
most	O
keyboards	B-Device
supporting	O
them	O
,	O
by	O
pressing	O
the	O
two	O
corresponding	O
deadkeys	O
in	O
any	O
order	O
,	O
followed	O
by	O
the	O
letter	O
key	O
.	O
</s>
<s>
Therefore	O
,	O
these	O
dead	B-Device
keys	I-Device
are	O
chained	O
,	O
which	O
means	O
that	O
the	O
second	O
keystroke	O
does	O
not	O
trigger	O
any	O
insertion	O
,	O
the	O
system	O
being	O
still	O
awaiting	O
another	O
key	O
press	O
.	O
</s>
<s>
This	O
chained	O
dead	B-Device
key	I-Device
behavior	O
is	O
toggled	O
by	O
the	O
dead	B-Device
key	I-Device
flag	O
,	O
which	O
is	O
the	O
fourth	O
argument	O
of	O
the	O
DEADTRANS	O
function	O
(	O
after	O
the	O
base	O
character	B-General_Concept
code	I-General_Concept
,	O
the	O
diacritic	O
code	O
,	O
and	O
the	O
composed	O
character	B-General_Concept
code	I-General_Concept
)	O
.	O
</s>
<s>
Ifthis	O
flag	O
is	O
set	O
to	O
its	O
default	O
value	O
zero	O
,	O
the	O
composed	O
character	O
is	O
inserted	O
;	O
if	O
it	O
is	O
set	O
to	O
one	O
,	O
the	O
composed	O
character	B-General_Concept
code	I-General_Concept
is	O
handled	O
as	O
another	O
diacritic	O
code	O
like	O
those	O
due	O
to	O
dead	B-Device
key	I-Device
presses	O
,	O
and	O
occurs	O
typically	O
as	O
a	O
second	O
argument	O
in	O
other	O
dead	O
list	O
entries	O
.	O
</s>
<s>
Chaining	O
dead	B-Device
keys	I-Device
allows	O
for	O
compose	O
key	O
emulation	O
by	O
simply	O
using	O
the	O
dead	B-Device
key	I-Device
feature	O
.	O
</s>
<s>
This	O
may	O
be	O
performed	O
either	O
with	O
proprietary	O
keyboard	B-Device
editing	O
software	O
,	O
or	O
with	O
driver	O
development	O
kits	O
.	O
</s>
<s>
A	O
key	O
may	O
function	O
as	O
a	O
dead	B-Device
key	I-Device
by	O
default	O
,	O
and	O
many	O
non-English	O
keyboard	B-Device
layouts	O
in	O
particular	O
have	O
dead	B-Device
keys	I-Device
directly	O
on	O
the	O
keyboard	B-Device
.	O
</s>
<s>
The	O
basic	O
US	O
keyboard	B-Device
does	O
not	O
have	O
any	O
dead	B-Device
keys	I-Device
,	O
but	O
the	O
US-International	O
keyboard	B-Device
layout	O
,	O
available	O
on	O
Windows	O
and	O
the	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
,	O
places	O
some	O
dead	B-Device
keys	I-Device
directly	O
on	O
similar-looking	O
punctuation	O
marks	O
.	O
</s>
<s>
Keyboards	B-Device
sold	O
in	O
most	O
of	O
the	O
rest	O
of	O
the	O
world	O
have	O
an	O
AltGr	B-Device
(	O
Alternative	O
graphic	O
)	O
key	O
,	O
which	O
gives	O
the	O
ability	O
to	O
modify	O
some	O
letters	O
directly	O
and	O
turns	O
others	O
into	O
dead	B-Device
keys	I-Device
(	O
depending	O
on	O
keyboard	B-Device
setting	O
)	O
.	O
</s>
<s>
Old	O
computer	O
systems	O
,	O
such	O
as	O
the	O
MSX	B-Operating_System
,	O
often	O
had	O
a	O
special	O
key	O
labeled	O
dead	B-Device
key	I-Device
,	O
which	O
in	O
combination	O
with	O
the	O
Ctrl	B-Device
and	O
Shift	B-Device
keys	I-Device
could	O
be	O
used	O
to	O
add	O
some	O
of	O
the	O
diacritics	O
commonly	O
needed	O
in	O
the	O
Western	O
European	O
languages	O
( ´	O
,	O
`	O
,	O
ˆ	O
and	O
¨	O
)	O
to	O
vowels	O
that	O
were	O
typed	O
subsequently	O
.	O
</s>
<s>
In	O
the	O
absence	O
of	O
a	O
default	O
dead	B-Device
key	I-Device
,	O
even	O
a	O
normal	O
printing	O
key	O
can	O
temporarily	O
be	O
altered	O
to	O
function	O
as	O
a	O
dead	B-Device
key	I-Device
by	O
simultaneously	O
holding	O
down	O
another	O
modifier	B-Device
key	I-Device
(	O
typically	O
AltGr	B-Device
or	O
Option	B-Device
)	O
.	O
</s>
<s>
In	O
Microsoft	B-Application
Word	I-Application
(	O
and	O
in	O
most	O
other	O
text-input	O
fields	O
)	O
,	O
using	O
the	O
Control	B-Device
key	I-Device
with	O
a	O
key	O
that	O
usually	O
resembles	O
the	O
diacritic	O
(	O
e.g.	O
</s>
<s>
^	O
for	O
a	O
circumflex	O
)	O
acts	O
as	O
a	O
dead	B-Device
key	I-Device
:	O
On	O
the	O
Macintosh	B-Device
,	O
many	O
keyboard	B-Device
layouts	O
employ	O
dead	B-Device
keys	I-Device
.	O
</s>
<s>
On	O
a	O
Macintosh	B-Device
,	O
pressing	O
one	O
of	O
these	O
Option-key	O
combinations	O
creates	O
the	O
accent	O
and	O
highlights	O
it	O
,	O
then	O
the	O
final	O
character	O
appears	O
when	O
the	O
key	O
for	O
the	O
base	O
character	O
is	O
pressed	O
.	O
</s>
<s>
For	O
users	O
with	O
US	O
keyboards	B-Device
,	O
access	O
to	O
many	O
more	O
diacritics	O
is	O
provided	O
by	O
the	O
"	O
US	O
International	O
"	O
keyboard	B-Device
layout	O
.	O
</s>
<s>
Users	O
with	O
UK	O
keyboards	B-Device
have	O
a	O
similar	O
option	B-Device
with	O
UK	O
extended	O
layout	O
;	O
many	O
other	O
national	O
settings	O
are	O
available	O
.	O
</s>
<s>
In	O
AmigaOS	B-Application
,	O
dead	B-Device
keys	I-Device
are	O
generated	O
by	O
pressing	O
in	O
combination	O
with	O
(	O
acute	O
)	O
,	O
(	O
grave	O
)	O
,	O
(	O
circumflex	O
)	O
,	O
(	O
tilde	O
)	O
or	O
(	O
trema	O
)	O
(	O
e.g.	O
,	O
the	O
ALT-F	O
combination	O
followed	O
by	O
the	O
a	O
key	O
generates	O
á	O
and	O
ALT-F	O
followed	O
by	O
e	O
generates	O
é	O
,	O
whereas	O
ALT-G	O
followed	O
by	O
a	O
generates	O
à	O
and	O
ALT-G	O
followed	O
by	O
e	O
generates	O
è	O
)	O
.	O
</s>
