<s>
In	O
computing	O
,	O
solid	B-General_Concept
compression	I-General_Concept
is	O
a	O
method	O
for	O
data	B-General_Concept
compression	I-General_Concept
of	O
multiple	O
files	O
,	O
wherein	O
all	O
the	O
uncompressed	B-General_Concept
files	O
are	O
concatenated	O
and	O
treated	O
as	O
a	O
single	O
data	O
block	O
.	O
</s>
<s>
Such	O
an	O
archive	O
is	O
called	O
a	O
solid	B-General_Concept
archive	I-General_Concept
.	O
</s>
<s>
It	O
is	O
used	O
natively	O
in	O
the	O
7z	O
and	O
RAR	O
formats	O
,	O
as	O
well	O
as	O
indirectly	O
in	O
tar-based	O
formats	O
such	O
as	O
.tar.gz	O
and	O
.tar.bz2	O
.	O
</s>
<s>
By	O
contrast	O
,	O
the	O
ZIP	B-General_Concept
format	I-General_Concept
is	O
not	O
solid	O
because	O
it	O
stores	O
separately	O
compressed	O
files	O
(	O
though	O
solid	B-General_Concept
compression	I-General_Concept
can	O
be	O
emulated	O
for	O
small	O
archives	O
by	O
combining	O
the	O
files	O
into	O
an	O
uncompressed	B-General_Concept
archive	O
file	O
and	O
then	O
compressing	O
that	O
archive	O
file	O
inside	O
a	O
second	O
compressed	O
ZIP	B-General_Concept
file	I-General_Concept
)	O
.	O
</s>
<s>
Compressed	O
file	O
formats	O
often	O
feature	O
both	O
compression	O
(	O
storing	O
the	O
data	O
in	O
a	O
small	O
space	O
)	O
and	O
archiving	B-Application
(	O
storing	O
multiple	O
files	O
and	O
metadata	O
in	O
a	O
single	O
file	O
)	O
.	O
</s>
<s>
The	O
order	O
matters	O
(	O
these	O
operations	O
do	O
not	O
commute	O
)	O
,	O
and	O
the	O
latter	O
is	O
solid	B-General_Concept
compression	I-General_Concept
.	O
</s>
<s>
In	O
Unix	O
,	O
compression	O
and	O
archiving	B-Application
are	O
traditionally	O
separate	O
operations	O
,	O
which	O
allows	O
one	O
to	O
understand	O
this	O
distinction	O
:	O
</s>
<s>
Compressing	O
individual	O
files	O
and	O
then	O
archiving	B-Application
would	O
be	O
a	O
tar	B-Application
gzip-compressed	O
files	O
this	O
is	O
very	O
uncommon	O
.	O
</s>
<s>
Archiving	B-Application
various	O
uncompressed	B-General_Concept
files	O
via	O
tar	B-Application
and	O
compressing	O
yields	O
a	O
compressed	O
archive	O
:	O
a	O
.tar.gz	B-Application
file	I-Application
this	O
is	O
solid	B-General_Concept
compression	I-General_Concept
.	O
</s>
<s>
non	O
solid	B-General_Concept
archive	I-General_Concept
:	O
</s>
<s>
solid	B-General_Concept
archive	I-General_Concept
:	O
</s>
<s>
Solid	B-General_Concept
compression	I-General_Concept
allows	O
for	O
much	O
better	O
compression	O
rates	O
when	O
all	O
the	O
files	O
are	O
similar	O
,	O
which	O
is	O
often	O
the	O
case	O
if	O
they	O
are	O
of	O
the	O
same	O
file	O
format	O
.	O
</s>
<s>
It	O
can	O
also	O
be	O
efficient	O
when	O
archiving	B-Application
a	O
large	O
number	O
of	O
small	O
files	O
.	O
</s>
<s>
On	O
the	O
other	O
hand	O
,	O
getting	O
a	O
single	O
file	O
out	O
of	O
a	O
solid	B-General_Concept
archive	I-General_Concept
requires	O
processing	O
all	O
the	O
files	O
before	O
it	O
,	O
so	O
modifying	O
solid	B-General_Concept
archives	I-General_Concept
could	O
be	O
slow	O
and	O
inconvenient	O
.	O
</s>
<s>
On	O
newer	O
formats	O
such	O
as	O
7-zip	O
,	O
there	O
is	O
a	O
solid	O
block	O
size	O
option	O
that	O
allows	O
for	O
the	O
concatenated	O
data	O
block	O
to	O
be	O
split	O
into	O
individually-compressed	O
smaller	O
blocks	O
,	O
so	O
that	O
only	O
a	O
limited	O
amount	O
of	O
data	O
in	O
the	O
block	O
must	O
be	O
processed	O
in	O
order	O
to	O
extract	O
one	O
file	O
.	O
</s>
<s>
Additionally	O
,	O
if	O
the	O
archive	O
becomes	O
even	O
slightly	O
damaged	O
,	O
some	O
of	O
the	O
data	O
(	O
sometimes	O
even	O
all	O
data	O
)	O
after	O
the	O
damaged	O
part	O
in	O
the	O
block	O
can	O
be	O
unusable	O
(	O
depending	O
on	O
the	O
compression	O
and	O
archiving	B-Application
format	O
)	O
,	O
whereas	O
in	O
a	O
non-solid	O
archive	O
format	O
,	O
usually	O
only	O
one	O
file	O
is	O
unusable	O
and	O
the	O
subsequent	O
files	O
can	O
usually	O
still	O
be	O
extracted	O
.	O
</s>
