<s>
In	O
automata	B-Application
theory	I-Application
,	O
a	O
deterministic	B-Application
pushdown	I-Application
automaton	I-Application
(	O
DPDA	B-Application
or	O
DPA	O
)	O
is	O
a	O
variation	O
of	O
the	O
pushdown	B-Application
automaton	I-Application
.	O
</s>
<s>
The	O
class	O
of	O
deterministic	B-Application
pushdown	I-Application
automata	I-Application
accepts	O
the	O
deterministic	O
context-free	O
languages	O
,	O
a	O
proper	O
subset	O
of	O
context-free	O
languages	O
.	O
</s>
<s>
A	O
deterministic	B-Application
pushdown	I-Application
automaton	I-Application
has	O
at	O
most	O
one	O
legal	O
transition	O
for	O
the	O
same	O
combination	O
of	O
input	O
symbol	O
,	O
state	O
,	O
and	O
top	O
stack	O
symbol	O
.	O
</s>
<s>
This	O
is	O
where	O
it	O
differs	O
from	O
the	O
nondeterministic	B-Application
pushdown	I-Application
automaton	I-Application
.	O
</s>
<s>
The	O
two	O
are	O
not	O
equivalent	O
for	O
the	O
deterministic	B-Application
pushdown	I-Application
automaton	I-Application
(	O
although	O
they	O
are	O
for	O
the	O
non-deterministic	O
pushdown	O
automaton	O
)	O
.	O
</s>
<s>
If	O
is	O
a	O
language	O
accepted	O
by	O
a	O
PDA	O
,	O
it	O
can	O
also	O
be	O
accepted	O
by	O
a	O
DPDA	B-Application
if	O
and	O
only	O
if	O
there	O
is	O
a	O
single	O
computation	O
from	O
the	O
initial	O
configuration	O
until	O
an	O
accepting	O
one	O
for	O
all	O
strings	O
belonging	O
to	O
.	O
</s>
<s>
If	O
can	O
be	O
accepted	O
by	O
a	O
PDA	O
it	O
is	O
a	O
context	O
free	O
language	O
and	O
if	O
it	O
can	O
be	O
accepted	O
by	O
a	O
DPDA	B-Application
it	O
is	O
a	O
deterministic	O
context-free	O
language	O
(	O
DCFL	O
)	O
.	O
</s>
<s>
This	O
makes	O
the	O
DPDA	B-Application
a	O
strictly	O
weaker	O
device	O
than	O
the	O
PDA	O
.	O
</s>
<s>
If	O
a	O
DPDA	B-Application
for	O
this	O
language	O
exists	O
,	O
and	O
it	O
sees	O
a	O
string	O
0n	O
,	O
it	O
must	O
use	O
its	O
stack	O
to	O
memorize	O
the	O
length	O
n	O
,	O
in	O
order	O
to	O
be	O
able	O
to	O
distinguish	O
its	O
possible	O
continuations	O
and	O
Hence	O
,	O
after	O
reading	O
comparing	O
the	O
post-	O
"	O
11	O
"	O
length	O
to	O
the	O
pre-	O
"	O
11	O
"	O
length	O
will	O
make	O
the	O
stack	O
empty	O
again	O
.	O
</s>
<s>
Restricting	O
the	O
DPDA	B-Application
to	O
a	O
single	O
state	O
reduces	O
the	O
class	O
of	O
languages	O
accepted	O
to	O
the	O
LL(1 )	O
languages	O
,	O
which	O
is	O
a	O
proper	O
subclass	O
of	O
the	O
DCFL	O
.	O
</s>
