<s>
PKZIP	B-Application
is	O
a	O
file	B-Application
archiving	I-Application
computer	B-Application
program	I-Application
,	O
notable	O
for	O
introducing	O
the	O
popular	O
ZIP	B-General_Concept
file	I-General_Concept
format	I-General_Concept
.	O
</s>
<s>
PKZIP	B-Application
was	O
first	O
introduced	O
for	O
MS-DOS	B-Application
on	O
the	O
IBM-PC	O
compatible	O
platform	O
in	O
1989	O
.	O
</s>
<s>
PKZIP	B-Application
was	O
originally	O
written	O
by	O
Phil	O
Katz	O
and	O
marketed	O
by	O
his	O
company	O
PKWARE	O
,	O
Inc	O
starting	O
in	O
1986	O
.	O
</s>
<s>
By	O
the	O
1970s	O
,	O
file	B-Application
archiving	I-Application
programs	O
were	O
distributed	O
as	O
standard	O
utilities	O
with	O
operating	O
systems	O
.	O
</s>
<s>
They	O
include	O
the	O
Unix	B-Application
utilities	I-Application
ar	O
,	O
shar	O
,	O
and	O
tar	B-Application
.	O
</s>
<s>
These	O
archives	O
could	O
optionally	O
be	O
passed	O
through	O
a	O
stream	O
compressor	O
utility	O
,	O
such	O
as	O
compress	B-Device
and	O
others	O
.	O
</s>
<s>
Other	O
archivers	O
also	O
appeared	O
during	O
the	O
1980s	O
,	O
including	O
ARC	B-Application
by	O
System	O
Enhancement	O
Associates	O
,	O
Inc	O
.	O
(	O
SEA	O
)	O
,	O
Rahul	O
Dhesi	O
's	O
ZOO	B-Application
,	O
Dean	O
W	O
.	O
Cooper	O
's	O
DWC	O
,	O
LHarc	B-Application
by	O
Haruhiko	O
Okomura	O
and	O
Haruyasu	O
Yoshizaki	O
and	O
ARJ	B-Application
which	O
stands	O
for	O
"	O
Archived	O
by	O
Robert	O
Jung	O
"	O
.	O
</s>
<s>
The	O
development	O
of	O
PKZIP	B-Application
was	O
first	O
announced	O
in	O
the	O
file	O
SOFTDEV.DOC	O
from	O
within	O
the	O
PKPAK	O
3.61	O
package	O
,	O
stating	O
it	O
would	O
develop	O
a	O
new	O
and	O
yet	O
unnamed	O
compression	O
program	O
.	O
</s>
<s>
Although	O
SEA	O
won	O
the	O
suit	O
,	O
it	O
lost	O
the	O
compression	O
war	O
,	O
as	O
the	O
user	O
base	O
migrated	O
to	O
PKZIP	B-Application
as	O
the	O
compressor	O
of	O
choice	O
.	O
</s>
<s>
Led	O
by	O
some	O
BBS	B-Application
sysops	O
who	O
refused	O
to	O
accept	O
or	O
offer	O
files	O
compressed	O
as	O
.ARC	B-Application
files	O
,	O
users	O
began	O
recompressing	O
any	O
old	O
archives	O
that	O
were	O
currently	O
stored	O
in	O
.ARC	B-Application
format	O
into	O
.ZIP	B-General_Concept
files	I-General_Concept
.	O
</s>
<s>
The	O
first	O
version	O
was	O
released	O
in	O
1989	O
,	O
as	O
a	O
DOS	B-Device
command-line	O
tool	O
,	O
distributed	O
under	O
shareware	B-License
model	O
with	O
a	O
US$25	O
registration	O
fee	O
(	O
US$47	O
with	O
manual	O
)	O
.	O
</s>
<s>
To	O
help	O
ensure	O
the	O
interoperability	O
of	O
the	O
ZIP	B-General_Concept
format	O
,	O
Phil	O
Katz	O
published	O
the	O
original	O
.ZIP	B-General_Concept
File	I-General_Concept
Format	O
Specification	O
in	O
the	O
APPNOTE.TXT	O
documentation	O
file	O
.	O
</s>
<s>
Originally	O
only	O
bundled	O
with	O
registered	O
versions	O
of	O
PKZIP	B-Application
,	O
it	O
was	O
later	O
available	O
on	O
the	O
PKWARE	O
site	O
.	O
</s>
<s>
The	O
specification	O
has	O
its	O
own	O
version	O
number	O
,	O
which	O
does	O
not	O
necessarily	O
correspond	O
to	O
the	O
PKZIP	B-Application
version	O
numbers	O
,	O
especially	O
with	O
PKZIP	B-Application
6	O
or	O
later	O
.	O
</s>
<s>
At	O
various	O
times	O
,	O
PKWARE	O
adds	O
preliminary	O
features	O
that	O
allows	O
PKZIP	B-Application
products	O
to	O
extract	O
archives	O
using	O
advanced	O
features	O
,	O
but	O
PKZIP	B-Application
products	O
that	O
create	O
such	O
archives	O
wo	O
n't	O
be	O
available	O
until	O
the	O
next	O
major	O
release	O
.	O
</s>
<s>
Although	O
popular	O
at	O
the	O
time	O
,	O
ZIP	B-General_Concept
archives	I-General_Concept
using	O
PKZIP	B-Application
1.0	O
compression	O
methods	O
are	O
now	O
rare	O
,	O
and	O
many	O
unzip	B-General_Concept
tools	O
such	O
as	O
7-Zip	B-Language
are	O
able	O
to	O
read	O
and	O
write	O
several	O
other	O
archive	O
formats	O
.	O
</s>
<s>
Shrinking	O
uses	O
dynamic	O
LZW	B-Algorithm
,	O
on	O
which	O
Unisys	O
held	O
patents	O
.	O
</s>
<s>
A	O
patent	O
for	O
the	O
Reduce	O
Algorithm	O
had	O
also	O
been	O
filed	O
on	O
June	O
19	O
,	O
1984	O
,	O
long	O
before	O
PKZIP	B-Application
was	O
produced	O
.	O
</s>
