<s>
compress	B-Device
is	O
a	O
Unix	B-Application
shell	I-Application
compression	B-General_Concept
program	I-General_Concept
based	O
on	O
the	O
LZW	B-Algorithm
compression	I-Algorithm
algorithm	I-Algorithm
.	O
</s>
<s>
Compared	O
to	O
gzip	B-Application
's	O
fastest	O
setting	O
,	O
compress	B-Device
is	O
slightly	O
slower	O
at	O
compression	O
,	O
slighty	O
faster	O
at	O
decompression	O
,	O
and	O
has	O
a	O
significantly	O
lower	O
compression	B-General_Concept
ratio	I-General_Concept
.	O
</s>
<s>
1.8	O
MiB	O
of	O
memory	O
is	O
used	O
to	O
compress	B-Device
the	O
Hutter	O
Prize	O
data	O
,	O
slightly	O
more	O
than	O
gzip	B-Application
's	O
slowest	O
setting	O
.	O
</s>
<s>
The	O
uncompress	B-Device
utility	O
will	O
restore	O
files	O
to	O
their	O
original	O
state	O
after	O
they	O
have	O
been	O
compressed	O
using	O
the	O
compress	B-Device
utility	O
.	O
</s>
<s>
If	O
no	O
files	O
are	O
specified	O
,	O
the	O
standard	O
input	O
will	O
be	O
uncompressed	B-General_Concept
to	O
the	O
standard	O
output	O
.	O
</s>
<s>
In	O
the	O
upcoming	O
POSIX	O
and	O
Single	O
Unix	B-Application
Specification	O
revision	O
,	O
it	O
is	O
planned	O
that	O
DEFLATE	B-Algorithm
algorithm	O
used	O
in	O
gzip	B-Application
format	O
be	O
supported	O
in	O
those	O
utilities	O
.	O
</s>
<s>
Files	O
compressed	O
by	O
compress	B-Device
are	O
typically	O
given	O
the	O
extension	O
"	O
.Z	B-Device
"	O
(	O
modeled	O
after	O
the	O
earlier	O
pack	B-Application
program	O
which	O
used	O
the	O
extension	O
"	O
.z	B-Device
"	O
)	O
.	O
</s>
<s>
Most	O
tar	B-Application
programs	O
will	O
pipe	B-Operating_System
their	O
data	O
through	O
compress	B-Device
when	O
given	O
the	O
command	B-Application
line	O
option	O
"	O
-Z	O
"	O
.	O
</s>
<s>
(	O
The	O
tar	B-Application
program	O
in	O
its	O
own	O
does	O
not	O
compress	B-Device
;	O
it	O
just	O
stores	O
multiple	O
files	O
within	O
one	O
tape	B-Application
archive	I-Application
.	O
)	O
</s>
<s>
Files	O
can	O
be	O
returned	O
to	O
their	O
original	O
state	O
using	O
uncompress	B-Device
.	O
</s>
<s>
The	O
usual	O
action	O
of	O
uncompress	B-Device
is	O
not	O
merely	O
to	O
create	O
an	O
uncompressed	B-General_Concept
copy	O
of	O
the	O
file	O
,	O
but	O
also	O
to	O
restore	O
the	O
timestamp	O
and	O
other	O
attributes	O
of	O
the	O
compressed	O
file	O
.	O
</s>
<s>
For	O
files	O
produced	O
by	O
compress	B-Device
on	O
other	O
systems	O
,	O
uncompress	B-Device
supports	O
9	O
-	O
to	O
16-bit	O
compression	O
.	O
</s>
<s>
The	O
LZW	B-Algorithm
algorithm	I-Algorithm
used	O
in	O
was	O
patented	O
by	O
Sperry	O
Research	O
Center	O
in	O
1983	O
.	O
</s>
<s>
Spencer	O
Thomas	O
of	O
the	O
University	O
of	O
Utah	O
took	O
this	O
article	O
and	O
implemented	O
in	O
1984	O
,	O
without	O
realizing	O
that	O
a	O
patent	O
was	O
pending	O
on	O
the	O
LZW	B-Algorithm
algorithm	I-Algorithm
.	O
</s>
<s>
The	O
GIF	O
image	O
format	O
also	O
incorporated	O
LZW	B-Algorithm
compression	I-Algorithm
in	O
this	O
way	O
,	O
and	O
Unisys	O
later	O
claimed	O
royalties	O
on	O
implementations	O
of	O
GIF	O
.	O
</s>
<s>
to	O
create	O
the	O
'	O
final	O
 '	O
(	O
4.0	O
)	O
version	O
of	O
and	O
published	O
it	O
as	O
free	O
software	O
to	O
the	O
'	O
net.sources	O
'	O
USENET	B-Application
group	O
in	O
1985	O
.	O
was	O
granted	O
in	O
1985	O
,	O
and	O
this	O
is	O
why	O
could	O
not	O
be	O
used	O
without	O
paying	O
royalties	O
to	O
Sperry	O
Research	O
,	O
which	O
was	O
eventually	O
merged	O
into	O
Unisys	O
.	O
</s>
<s>
has	O
fallen	O
out	O
of	O
favor	O
in	O
particular	O
user-groups	O
because	O
it	O
makes	O
use	O
of	O
the	O
LZW	B-Algorithm
algorithm	I-Algorithm
,	O
which	O
was	O
covered	O
by	O
a	O
Unisys	O
patent	O
because	O
of	O
this	O
,	O
gzip	B-Application
and	O
bzip2	B-Application
increased	O
in	O
popularity	O
on	O
Linux-based	O
operating	O
systems	O
due	O
to	O
their	O
alternative	O
algorithms	O
,	O
along	O
with	O
better	O
file	B-General_Concept
compression	I-General_Concept
.	O
</s>
<s>
compress	B-Device
has	O
,	O
however	O
,	O
maintained	O
a	O
presence	O
on	O
Unix	B-Application
and	O
BSD	B-Operating_System
systems	O
and	O
the	O
and	O
commands	O
have	O
also	O
been	O
ported	O
to	O
the	O
IBM	B-Application
i	I-Application
operating	O
system	O
.	O
</s>
<s>
The	O
US	O
LZW	B-Algorithm
patent	O
expired	O
in	O
2003	O
,	O
so	O
it	O
is	O
now	O
in	O
the	O
public	O
domain	O
in	O
the	O
United	O
States	O
.	O
</s>
<s>
All	O
patents	O
on	O
the	O
LZW	B-Algorithm
worldwide	O
have	O
also	O
expired	O
(	O
see	O
Graphics	O
Interchange	O
Format	O
#Unisys	O
and	O
LZW	B-Algorithm
patent	O
enforcement	O
)	O
.	O
</s>
<s>
In	O
the	O
up-coming	O
POSIX	O
and	O
Single	O
Unix	B-Application
Specification	O
revision	O
,	O
it	O
is	O
planned	O
that	O
DEFLATE	B-Algorithm
algorithm	O
used	O
in	O
gzip	B-Application
format	O
be	O
supported	O
in	O
those	O
utilities	O
.	O
</s>
<s>
LZW	B-Algorithm
does	O
n't	O
require	O
any	O
alignment	O
.	O
</s>
<s>
This	O
bug	O
is	O
a	O
part	O
of	O
original	O
UNIX	B-Application
compress	B-Device
,	O
ncompress	O
,	O
gzip	B-Application
and	O
even	O
windows	O
port	O
.	O
</s>
<s>
All	O
application/x	O
-compress	O
files	O
were	O
created	O
using	O
this	O
bug	O
.	O
</s>
<s>
Some	O
compress	B-Device
implementations	O
write	O
random	O
bits	O
from	O
uninitialized	O
buffer	O
as	O
alignment	O
bits	O
.	O
</s>
<s>
compress	B-Device
was	O
standardized	O
in	O
X/Open	O
CAE	O
Specification	O
in	O
1994	O
,	O
and	O
further	O
in	O
The	O
Open	O
Group	O
Base	O
Specifications	O
,	O
Issue	O
6	O
and	O
7	O
.	O
</s>
<s>
Linux	B-Application
Standard	I-Application
Base	I-Application
does	O
not	O
requires	O
compress	B-Device
.	O
</s>
<s>
compress	B-Device
is	O
often	O
not	O
installed	O
by	O
default	O
in	O
Linux	B-Application
distributions	O
,	O
but	O
can	O
be	O
installed	O
from	O
an	O
additional	O
package	O
.	O
</s>
<s>
compress	B-Device
is	O
available	O
for	O
FreeBSD	O
,	O
OpenBSD	O
,	O
MINIX	O
,	O
Solaris	O
and	O
AIX	O
.	O
</s>
<s>
compress	B-Device
is	O
allowed	O
for	O
Point-to-Point	B-Protocol
Protocol	I-Protocol
in	O
and	O
for	O
HTTP/1.1	B-Protocol
in	O
,	O
though	O
it	O
is	O
rarely	O
used	O
in	O
modern	O
deployments	O
as	O
the	O
better	O
deflate/gzip	O
is	O
available	O
.	O
</s>
