<s>
Adaptive	B-Algorithm
Huffman	I-Algorithm
coding	I-Algorithm
(	O
also	O
called	O
Dynamic	B-Algorithm
Huffman	I-Algorithm
coding	I-Algorithm
)	O
is	O
an	O
adaptive	B-Algorithm
coding	I-Algorithm
technique	O
based	O
on	O
Huffman	B-General_Concept
coding	I-General_Concept
.	O
</s>
<s>
The	O
benefit	O
of	O
one-pass	O
procedure	O
is	O
that	O
the	O
source	O
can	O
be	O
encoded	O
in	O
real	O
time	O
,	O
though	O
it	O
becomes	O
more	O
sensitive	O
to	O
transmission	O
errors	O
,	O
since	O
just	O
a	O
single	O
loss	O
ruins	O
the	O
whole	O
code	O
,	O
requiring	O
error	B-Error_Name
detection	I-Error_Name
and	I-Error_Name
correction	I-Error_Name
.	O
</s>
<s>
There	O
are	O
a	O
number	O
of	O
implementations	O
of	O
this	O
method	O
,	O
the	O
most	O
notable	O
are	O
FGK	B-Algorithm
(	O
Faller-Gallager-Knuth	O
)	O
and	O
Vitter	B-Algorithm
algorithm	I-Algorithm
.	O
</s>
<s>
It	O
is	O
an	O
online	O
coding	O
technique	O
based	O
on	O
Huffman	B-General_Concept
coding	I-General_Concept
.	O
</s>
<s>
In	O
a	O
FGK	B-Algorithm
Huffman	B-General_Concept
tree	I-General_Concept
,	O
a	O
special	O
external	O
node	O
,	O
called	O
0-node	O
,	O
is	O
used	O
to	O
identify	O
a	O
newly	O
coming	O
character	O
.	O
</s>
<s>
Most	O
importantly	O
,	O
we	O
have	O
to	O
adjust	O
the	O
FGK	B-Algorithm
Huffman	B-General_Concept
tree	I-General_Concept
if	O
necessary	O
,	O
and	O
finally	O
update	O
the	O
frequency	O
of	O
related	O
nodes	O
.	O
</s>
<s>
Since	O
the	O
FGK	B-Algorithm
Algorithm	I-Algorithm
has	O
some	O
drawbacks	O
about	O
the	O
node-or-subtree	O
swapping	O
,	O
Vitter	O
proposed	O
another	O
algorithm	O
to	O
improve	O
it	O
.	O
</s>
<s>
For	O
the	O
convenience	O
of	O
explanation	O
this	O
step	O
does	O
n't	O
exactly	O
follow	O
Vitter	B-Algorithm
's	I-Algorithm
algorithm	I-Algorithm
,	O
but	O
the	O
effects	O
are	O
equivalent	O
.	O
</s>
