<s>
xv	B-Application
is	O
a	O
shareware	B-License
program	O
written	O
by	O
John	O
Bradley	O
to	O
display	O
and	O
modify	O
digital	O
images	O
under	O
the	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
.	O
</s>
<s>
While	O
popular	O
in	O
the	O
early	O
1990s	O
(	O
"	O
XV	B-Application
is	O
widely	O
considered	O
to	O
be	O
the	O
preeminent	O
image	B-Application
viewer	I-Application
for	O
the	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
"	O
)	O
,	O
no	O
official	O
releases	O
have	O
been	O
made	O
since	O
December	O
1994	O
.	O
</s>
<s>
Bradley	O
was	O
unable	O
to	O
negotiate	O
the	O
LZW	B-Algorithm
patent	O
licence	O
necessary	O
for	O
encoding	O
the	O
then-popular	O
GIF	O
format	O
.	O
</s>
<s>
Until	O
at	O
least	O
2000	O
,	O
Bradley	O
collected	O
third-party	O
updates	O
to	O
xv	B-Application
,	O
for	O
example	O
,	O
support	O
for	O
the	O
PNG	O
image	O
format	O
.	O
</s>
<s>
These	O
were	O
published	O
as	O
source	O
code	O
patches	B-Application
only	O
.	O
</s>
<s>
Additional	O
patches	B-Application
are	O
still	O
(	O
)	O
created	O
and	O
maintained	O
by	O
volunteers	O
.	O
</s>
<s>
xv	B-Application
can	O
be	O
run	O
from	O
either	O
the	O
command	O
line	O
or	O
through	O
a	O
graphical	O
interface	O
.	O
</s>
<s>
While	O
this	O
concept	O
limits	O
what	O
xv	B-Application
can	O
do	O
compared	O
to	O
some	O
alternatives	O
,	O
the	O
functionality	O
it	O
provides	O
can	O
be	O
applied	O
very	O
conveniently	O
and	O
efficiently	O
.	O
</s>
