<s>
for	O
writing	O
Ruby-related	O
documents	O
.	O
</s>
<s>
It	O
can	O
be	O
embedded	O
in	O
Ruby	B-Language
source	O
code	O
.	O
</s>
<s>
In	O
modern	O
Ruby	B-Language
,	O
developers	O
tend	O
to	O
write	O
documents	O
in	O
RDoc	B-Protocol
instead	O
of	O
RD	O
.	O
</s>
<s>
Originally	O
,	O
most	O
documentation	O
in	O
the	O
Ruby	B-Language
world	O
,	O
including	O
for	O
Ruby	B-Language
itself	O
,	O
had	O
been	O
written	O
in	O
RD	O
.	O
</s>
<s>
Then	O
in	O
2002	O
,	O
much	O
of	O
it	O
was	O
converted	O
to	O
RDoc	B-Protocol
format	O
.	O
</s>
<s>
Although	O
,	O
the	O
Japanese	O
version	O
of	O
the	O
Ruby	B-Language
Reference	O
Manual	O
still	O
remains	O
in	O
RD	O
format	O
.	O
</s>
<s>
Most	O
end-users	O
however	O
experience	O
it	O
after	O
it	O
has	O
been	O
converted	O
into	O
HTML	O
or	O
man	B-Protocol
pages	I-Protocol
.	O
</s>
<s>
RD	O
can	O
be	O
embedded	O
in	O
Ruby	B-Language
code	O
,	O
and	O
pure	O
RD	O
files	O
usually	O
have	O
the	O
extension	O
.rd	O
.	O
</s>
