<s>
The	O
Alt	B-Device
key	I-Device
(	O
pronounced	O
or	O
)	O
on	O
a	O
computer	O
keyboard	O
is	O
used	O
to	O
change	O
(	O
alternate	O
)	O
the	O
function	O
of	O
other	O
pressed	O
keys	O
.	O
</s>
<s>
Thus	O
,	O
the	O
Alt	B-Device
key	I-Device
is	O
a	O
modifier	B-Device
key	I-Device
,	O
used	O
in	O
a	O
similar	O
fashion	O
to	O
the	O
Shift	B-Device
key	I-Device
.	O
</s>
<s>
For	O
example	O
,	O
simply	O
pressing	O
A	O
will	O
type	O
the	O
letter	O
'	O
a	O
 '	O
,	O
but	O
holding	O
down	O
the	O
Alt	B-Device
key	I-Device
while	O
pressing	O
A	O
will	O
cause	O
the	O
computer	O
to	O
perform	O
an	O
function	O
,	O
which	O
varies	O
from	O
program	B-Application
to	O
program	B-Application
.	O
</s>
<s>
The	O
key	O
is	O
located	O
on	O
either	O
side	O
of	O
the	O
space	B-Device
bar	I-Device
,	O
but	O
in	O
non-US	O
PC	O
keyboard	O
layouts	O
,	O
rather	O
than	O
a	O
second	O
Alt	B-Device
key	I-Device
,	O
there	O
is	O
an	O
'	O
Alt	B-Device
Gr	I-Device
 '	O
key	O
to	O
the	O
right	O
of	O
the	O
space	B-Device
bar	I-Device
.	O
</s>
<s>
With	O
some	O
keyboard	O
mappings	O
(	O
such	O
as	O
US-International	O
)	O
,	O
the	O
right	B-Device
Alt	I-Device
key	I-Device
can	O
be	O
reconfigured	O
to	O
function	O
as	O
an	O
AltGr	B-Device
key	I-Device
although	O
not	O
engraved	O
as	O
such	O
.	O
</s>
<s>
The	O
standardized	O
keyboard	O
symbol	O
for	O
the	O
Alt	B-Device
key	I-Device
,	O
(	O
which	O
may	O
be	O
used	O
when	O
the	O
usual	O
Latin	O
lettering	O
"	O
Alt	O
"	O
is	O
not	O
preferred	O
for	O
labeling	O
the	O
key	O
)	O
is	O
given	O
in	O
ISO/IEC	O
9995-7	O
as	O
symbol	O
25	O
,	O
and	O
in	O
ISO	O
7000	O
"	O
Graphical	O
symbols	O
for	O
use	O
on	O
equipment	O
"	O
as	O
symbol	O
ISO-7000-2105	O
.	O
</s>
<s>
Macintosh	B-Device
keyboards	O
equate	O
the	O
Alt	B-Device
key	I-Device
with	O
the	O
key	O
,	O
which	O
has	O
its	O
own	O
symbol	O
,	O
similar	O
to	O
that	O
of	O
the	O
ISO	O
standard	O
.	O
</s>
<s>
The	O
Alt	B-Device
key	I-Device
should	O
not	O
be	O
confused	O
with	O
the	O
Altmode	O
key	O
(	O
sometimes	O
also	O
labelled	O
Alt	O
)	O
on	O
some	O
Teletype	O
and	O
ASCII	O
terminals	O
,	O
which	O
is	O
a	O
synonym	O
for	O
the	O
ASCII	O
escape	O
character	O
.	O
</s>
<s>
The	O
Alt	B-Device
key	I-Device
has	O
come	O
to	O
replace	O
the	O
Meta	B-Device
key	I-Device
of	O
the	O
old	O
MIT	O
keyboards	O
.	O
</s>
<s>
Since	O
the	O
1990s	O
Alt	O
has	O
been	O
printed	O
on	O
the	O
Option	B-Device
key	I-Device
(	O
)	O
on	O
most	O
Mac	B-Device
keyboards	O
.	O
</s>
<s>
Alt	O
is	O
used	O
in	O
non-Mac	O
software	O
,	O
such	O
as	O
non-macOS	O
Unix	O
and	O
Windows	O
programs	O
,	O
but	O
in	O
macOS	B-Application
it	O
is	O
always	O
referred	O
to	O
as	O
the	O
Option	B-Device
key	I-Device
.	O
</s>
<s>
The	O
Option	B-Device
key	I-Device
's	O
behaviour	O
in	O
macOS	B-Application
differs	O
slightly	O
from	O
that	O
of	O
the	O
Windows	O
Alt	B-Device
key	I-Device
(	O
it	O
is	O
used	O
as	O
a	O
modifier	O
rather	O
than	O
to	O
access	O
pull-down	O
menus	O
,	O
for	O
example	O
)	O
.	O
</s>
<s>
may	O
restart	O
the	O
computer	O
(	O
its	O
original	O
function	O
)	O
;	O
in	O
some	O
operating	O
systems	O
it	O
brings	O
up	O
a	O
task	B-General_Concept
manager	I-General_Concept
-	O
see	O
Control-Alt-Delete	B-Device
.	O
</s>
<s>
brings	O
up	O
the	O
Force	B-Operating_System
Quit	I-Operating_System
window	O
in	O
Apple	O
's	O
macOS	B-Application
,	O
see	O
Option	B-Device
key	I-Device
.	O
</s>
<s>
usually	O
causes	O
the	O
X	B-Operating_System
display	O
server	O
to	O
shut	O
down	O
or	O
to	O
restart	O
,	O
see	O
Control-Alt-Backspace	O
.	O
</s>
<s>
On	O
Linux	B-Application
,	O
this	O
is	O
done	O
using	O
Super+Alt	O
.	O
</s>
<s>
(	O
The	O
Linux	B-Application
"	B-Device
Super	I-Device
"	I-Device
key	I-Device
is	O
the	O
physically	O
the	O
same	O
as	O
the	O
Windows	B-Device
key	I-Device
.	O
)	O
</s>
<s>
When	O
only	O
holding	O
Alt	O
while	O
dragging	O
with	O
the	O
mouse	O
on	O
Linux	B-Application
(	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
)	O
,	O
the	O
window	O
is	O
moved	O
.	O
</s>
<s>
In	O
Microsoft	B-Application
Windows	I-Application
,	O
holding	O
down	O
the	O
Alt	B-Device
key	I-Device
while	O
typing	O
in	O
numbers	O
(	O
often	O
referred	O
to	O
as	O
Alt	O
codes	O
)	O
on	O
the	O
numeric	B-Device
keypad	I-Device
allows	O
the	O
user	O
to	O
type	O
special	O
characters	O
not	O
normally	O
available	O
on	O
the	O
keyboard	O
.	O
</s>
<s>
For	O
example	O
,	O
holding	O
down	O
Alt	O
while	O
typing	O
0225	O
(	O
)	O
on	O
the	O
numeric	B-Device
keypad	I-Device
will	O
result	O
in	O
,	O
the	O
character	O
at	O
225	O
in	O
the	O
(	O
Western	O
Latin	O
)	O
code	O
page	O
1252	O
.	O
</s>
<s>
Some	O
computers	O
work	O
the	O
same	O
if	O
the	O
Num	B-Device
Lock	I-Device
key	I-Device
is	O
on	O
.	O
</s>
<s>
On	O
a	O
Macintosh	B-Device
,	O
the	O
Alt	B-Device
key	I-Device
is	O
called	O
the	O
Option	B-Device
key	I-Device
.	O
</s>
<s>
The	O
diagram	O
below	O
shows	O
the	O
special	O
characters	O
a	O
US	O
Mac	B-Device
keyboard	O
will	O
produce	O
when	O
the	O
Option	B-Device
key	I-Device
is	O
pressed	O
.	O
</s>
<s>
The	O
additional	O
characters	O
a	O
Mac	B-Device
will	O
produce	O
are	O
a	O
combination	O
of	O
both	O
the	O
key	O
and	O
the	O
key	O
pressed	O
down	O
together	O
.	O
</s>
<s>
When	O
a	O
user	O
presses	O
the	O
key	O
by	O
itself	O
on	O
Microsoft	B-Application
Windows	I-Application
,	O
that	O
moves	O
keyboard	O
focus	O
to	O
the	O
menu	O
bar	O
of	O
the	O
application	O
having	O
keyboard	O
focus	O
,	O
and	O
the	O
key	O
is	O
not	O
delivered	O
to	O
the	O
application	O
.	O
</s>
<s>
On	O
other	O
platforms	O
,	O
for	O
example	O
Ubuntu	B-Operating_System
,	O
the	O
key	O
pressed	O
by	O
itself	O
may	O
invoke	O
another	O
application	O
and	O
not	O
be	O
delivered	O
to	O
the	O
application	O
having	O
keyboard	O
focus	O
.	O
</s>
<s>
In	O
Ubuntu	B-Operating_System
16.04	O
,	O
pressing	O
the	O
key	O
opens	O
the	O
HUD	O
,	O
which	O
is	O
an	O
input	O
field	O
that	O
lets	O
the	O
user	O
perform	O
menu	O
commands	O
such	O
as	O
opening	O
a	O
file	O
,	O
or	O
creating	O
a	O
new	O
file	O
.	O
</s>
