<s>
A	O
portable	B-Application
application	I-Application
(	O
portable	B-Application
app	I-Application
)	O
,	O
sometimes	O
also	O
called	O
standalone	O
,	O
is	O
a	O
program	B-Application
designed	O
to	O
read	O
and	O
write	O
its	O
configuration	O
settings	O
into	O
an	O
accessible	O
folder	O
in	O
the	O
computer	O
,	O
usually	O
in	O
the	O
folder	O
where	O
the	O
portable	B-Application
application	I-Application
can	O
be	O
found	O
.	O
</s>
<s>
This	O
makes	O
it	O
easier	O
to	O
transfer	O
the	O
program	B-Application
with	O
the	O
user	O
's	O
preferences	O
and	O
data	O
between	O
different	O
computers	O
.	O
</s>
<s>
A	O
program	B-Application
that	O
does	O
n't	O
have	O
any	O
configuration	O
options	O
can	O
also	O
be	O
a	O
portable	B-Application
application	I-Application
.	O
</s>
<s>
Portable	B-Application
applications	I-Application
can	O
be	O
stored	O
on	O
any	O
data	B-General_Concept
storage	I-General_Concept
device	I-General_Concept
,	O
including	O
internal	O
mass	B-Device
storage	I-Device
,	O
a	O
file	B-General_Concept
share	I-General_Concept
,	O
cloud	B-Application
storage	I-Application
or	O
external	O
storage	O
such	O
as	O
USB	O
drives	O
and	O
floppy	B-Device
disks	I-Device
—	O
storing	O
its	O
program	B-Application
files	I-Application
and	O
any	O
configuration	O
information	O
and	O
data	O
on	O
the	O
storage	B-General_Concept
medium	I-General_Concept
alone	O
.	O
</s>
<s>
If	O
no	O
configuration	O
information	O
is	O
required	O
a	O
portable	O
program	B-Application
can	O
be	O
run	O
from	O
read-only	O
storage	O
such	O
as	O
CD-ROMs	B-Device
and	O
DVD-ROMs	O
.	O
</s>
<s>
Some	O
applications	O
are	O
available	O
in	O
both	O
installable	B-Operating_System
and	O
portable	O
versions	O
.	O
</s>
<s>
Examples	O
might	O
include	O
/portable	O
to	O
simply	O
instruct	O
the	O
program	B-Application
to	O
behave	O
as	O
a	O
portable	O
program	B-Application
,	O
or	O
--cfg	O
=	O
/path/inifile	O
to	O
specify	O
the	O
configuration	O
file	O
location	O
.	O
</s>
<s>
Like	O
any	O
application	O
,	O
portable	B-Application
applications	I-Application
must	O
be	O
compatible	O
with	O
the	O
computer	O
system	O
hardware	O
and	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
Depending	O
on	O
the	O
operating	B-General_Concept
system	I-General_Concept
,	O
portability	O
is	O
more	O
or	O
less	O
complex	O
to	O
implement	O
;	O
to	O
operating	B-General_Concept
systems	I-General_Concept
such	O
as	O
AmigaOS	B-Application
,	O
all	O
applications	O
are	O
by	O
definition	O
portable	O
.	O
</s>
<s>
A	O
portable	B-Application
application	I-Application
does	O
not	O
leave	O
its	O
files	O
or	O
settings	O
on	O
the	O
host	O
computer	O
or	O
modify	O
the	O
existing	O
system	O
and	O
its	O
configuration	O
.	O
</s>
<s>
The	O
application	O
does	O
not	O
write	O
to	O
the	O
Windows	B-Protocol
registry	I-Protocol
nor	O
stores	O
its	O
configuration	O
files	O
(	O
such	O
as	O
an	O
INI	B-Protocol
file	I-Protocol
)	O
in	O
the	O
user	O
's	O
profile	B-Application
;	O
instead	O
,	O
it	O
stores	O
its	O
configuration	O
files	O
in	O
the	O
portable	O
directory	O
.	O
</s>
<s>
Another	O
requirement	O
,	O
since	O
file	B-Application
paths	I-Application
will	O
often	O
differ	O
on	O
changing	O
computers	O
due	O
to	O
variation	O
in	O
drive	O
letter	O
assignments	O
,	O
is	O
the	O
need	O
for	O
applications	O
to	O
store	O
them	O
in	O
a	O
relative	O
format	O
.	O
</s>
<s>
A	O
common	O
technique	O
for	O
such	O
programs	O
is	O
the	O
use	O
of	O
a	O
launcher	O
program	B-Application
to	O
copy	O
necessary	O
settings	O
and	O
files	O
to	O
the	O
host	O
computer	O
when	O
the	O
application	O
starts	O
and	O
move	O
them	O
back	O
to	O
the	O
application	O
's	O
directory	O
when	O
it	O
closes	O
.	O
</s>
<s>
An	O
alternative	O
strategy	O
for	O
achieving	O
application	B-Application
portability	I-Application
within	O
Windows	O
,	O
without	O
requiring	O
application	O
source	O
code	O
changes	O
,	O
is	O
application	B-Operating_System
virtualization	I-Operating_System
:	O
An	O
application	O
is	O
"	O
sequenced	O
"	O
or	O
"	O
packaged	O
"	O
against	O
a	O
runtime	O
layer	O
that	O
transparently	O
intercepts	O
its	O
file	O
system	O
and	O
registry	O
calls	O
,	O
then	O
redirects	O
these	O
to	O
other	O
persistent	O
storage	O
without	O
the	O
application	O
's	O
knowledge	O
.	O
</s>
<s>
The	O
same	O
approach	O
is	O
used	O
for	O
individual	O
application	O
components	O
:	O
run-time	B-Library
libraries	I-Library
,	O
COM	B-Application
components	O
or	O
ActiveX	B-Application
,	O
not	O
only	O
for	O
the	O
entire	O
application	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
when	O
individual	O
components	O
are	O
ported	O
in	O
such	O
manner	O
they	O
are	O
able	O
to	O
be	O
:	O
integrated	O
into	O
original	O
portable	B-Application
applications	I-Application
,	O
repeatedly	O
instantiated	O
(	O
virtually	O
installed	O
)	O
with	O
different	O
configurations/settings	O
on	O
the	O
same	O
operating	B-General_Concept
system	I-General_Concept
(	O
OS	O
)	O
without	O
mutual	O
conflicts	O
.	O
</s>
<s>
As	O
the	O
ported	O
components	O
do	O
not	O
affect	O
the	O
OS-protected	O
related	O
entities	O
(	O
registry	O
and	O
files	O
)	O
,	O
the	O
components	O
will	O
not	O
require	O
administrative	B-Application
privileges	I-Application
for	O
installation	O
and	O
management	O
.	O
</s>
<s>
Microsoft	O
saw	O
the	O
need	O
for	O
an	O
application-specific	O
registry	O
for	O
its	O
Windows	O
operating	B-General_Concept
system	I-General_Concept
as	O
far	O
back	O
as	O
2005	O
.	O
</s>
<s>
It	O
eventually	O
incorporated	O
some	O
of	O
this	O
technology	O
,	O
using	O
the	O
techniques	O
mentioned	O
above	O
,	O
via	O
its	O
Application	O
Compatibility	O
Database	O
using	O
its	O
Detours	O
code	O
library	O
,	O
into	O
Windows	B-Application
XP	I-Application
.	O
</s>
<s>
It	O
did	O
not	O
make	O
any	O
of	O
this	O
technology	O
available	O
via	O
its	O
system	O
APIs	B-General_Concept
.	O
</s>
<s>
Whereas	O
many	O
Windows	O
programs	O
assume	O
the	O
user	O
is	O
an	O
administrator	B-Application
—	O
something	O
very	O
prevalent	O
in	O
the	O
days	O
of	O
Windows	O
95/98/ME	O
(	O
and	O
to	O
some	O
degree	O
in	O
Windows	O
XP/2000	O
,	O
though	O
not	O
in	O
Windows	B-Application
Vista	I-Application
or	O
Windows	B-Device
7	I-Device
)	O
—	O
such	O
would	O
quickly	O
result	O
in	O
"	O
Permission	O
denied	O
"	O
errors	O
in	O
Unix-like	O
environments	O
since	O
users	O
will	O
be	O
in	O
an	O
unprivileged	O
state	O
much	O
more	O
often	O
.	O
</s>
<s>
$	O
HOME/.w3m	O
for	O
the	O
w3m	B-Application
browser	O
)	O
.	O
</s>
<s>
The	O
dynamic	O
linker	B-Application
provides	O
an	O
environment	O
variable	O
LD_LIBRARY_PATH	O
that	O
programs	O
can	O
use	O
to	O
load	O
libraries	O
from	O
non-standard	O
directories	O
.	O
</s>
<s>
adapting	O
a	O
script	O
or	O
environment	O
variable	O
)	O
on	O
varying	O
directory	B-Application
paths	I-Application
can	O
be	O
achieved	O
with	O
the	O
GCC	B-Application
Linker	B-Application
option	O
$ORIGIN	O
which	O
allows	O
a	O
relative	O
library	O
search	O
path	O
.	O
</s>
<s>
Not	O
all	O
programs	O
honor	O
this	O
—	O
some	O
completely	O
ignore	O
$HOME	O
and	O
instead	O
do	O
a	O
user	O
look-up	O
in	O
/etc/passwd	O
to	O
find	O
the	O
home	B-Application
directory	I-Application
,	O
therefore	O
thwarting	O
portability	O
.	O
</s>
<s>
There	O
are	O
also	O
cross-distro	O
package	O
formats	O
that	O
do	O
not	O
require	O
admin	O
rights	O
to	O
run	O
,	O
like	O
Autopackage	B-Application
,	O
klik	B-Application
(	O
now	O
called	O
AppImage	B-Application
)	O
,	O
or	O
CDE	O
,	O
but	O
which	O
gained	O
only	O
limited	O
acceptance	O
and	O
support	O
in	O
the	O
Linux	O
community	O
in	O
the	O
2000s	O
.	O
</s>
<s>
Around	O
2015	O
the	O
idea	O
of	O
portable	O
and	O
distro	O
independent	O
packing	O
for	O
the	O
Linux	O
ecosystem	O
got	O
more	O
traction	O
when	O
Linus	O
Torvalds	O
discussed	O
this	O
topic	O
on	O
the	O
DebConf	O
2014	O
and	O
endorsed	O
later	O
AppImage	B-Application
for	O
his	O
dive	O
log	O
application	O
Subsurface	O
.	O
</s>
<s>
For	O
instance	O
,	O
MuseScore	B-Language
and	O
Krita	B-Application
followed	O
in	O
2016	O
and	O
started	O
to	O
use	O
AppImage	B-Application
builds	O
for	O
software	O
deployment	O
.	O
</s>
<s>
RedHat	O
released	O
in	O
2016	O
the	O
Flatpak	B-Language
system	O
,	O
which	O
is	O
a	O
successor	O
of	O
Alexander	O
Larsson	O
's	O
glick	O
project	O
which	O
was	O
inspired	O
by	O
klik	B-Application
(	O
now	O
AppImage	B-Application
)	O
.	O
</s>
<s>
Similarly	O
,	O
Canonical	O
released	O
in	O
2016	O
Snap	B-Application
packages	I-Application
for	O
Ubuntu	B-Operating_System
and	O
many	O
other	O
Linux	O
distros	O
.	O
</s>
<s>
Examples	O
include	O
Mozilla	B-Application
Firefox	I-Application
,	O
Skype	B-Application
and	O
Google	B-Application
Chrome	I-Application
which	O
do	O
not	O
require	O
admin	O
access	O
and	O
do	O
not	O
need	O
to	O
be	O
placed	O
into	O
a	O
central	O
,	O
restricted	O
area	O
.	O
</s>
<s>
Developers	O
can	O
create	O
Mac	O
product	O
installers	B-Operating_System
which	O
allow	O
the	O
user	O
to	O
perform	O
a	O
home	B-Application
directory	I-Application
install	O
,	O
labelled	O
"	O
Install	O
for	O
me	B-Device
only	O
"	O
in	O
the	O
Installer	B-Operating_System
user	O
interface	O
.	O
</s>
