<s>
Pack	O
is	O
a	O
legacy	O
Unix	B-Application
shell	I-Application
compression	B-General_Concept
program	I-General_Concept
based	O
on	O
Huffman	B-General_Concept
coding	I-General_Concept
.	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>
Although	O
obsolete	O
,	O
support	O
for	O
packed	O
files	O
exists	O
in	O
modern	O
compression	O
tools	O
such	O
as	O
gzip	B-Application
and	O
7-zip	B-Language
.	O
</s>
<s>
Files	O
compressed	O
by	O
pack	O
are	O
typically	O
given	O
the	O
extension	O
"	O
.z	B-Device
"	O
(	O
not	O
to	O
be	O
confused	O
with	O
the	O
"	O
.Z	B-Device
"	O
of	O
compress	B-Device
)	O
.	O
</s>
