<s>
In	O
computation	O
theory	O
,	O
the	O
Blum	B-Application
–	I-Application
Shub	I-Application
–	I-Application
Smale	I-Application
machine	I-Application
,	O
or	O
BSS	O
machine	O
,	O
is	O
a	O
model	O
of	O
computation	O
introduced	O
by	O
Lenore	O
Blum	O
,	O
Michael	O
Shub	O
and	O
Stephen	O
Smale	O
,	O
intended	O
to	O
describe	O
computations	O
over	O
the	O
real	O
numbers	O
.	O
</s>
<s>
Essentially	O
,	O
a	O
BSS	O
machine	O
is	O
a	O
Random	B-Application
Access	I-Application
Machine	I-Application
with	O
registers	O
that	O
can	O
store	O
arbitrary	O
real	O
numbers	O
and	O
that	O
can	O
compute	O
rational	O
functions	O
over	O
reals	O
in	O
a	O
single	O
time	O
step	O
.	O
</s>
<s>
It	O
is	O
often	O
referred	O
to	O
as	O
Real	B-General_Concept
RAM	I-General_Concept
model	O
.	O
</s>
<s>
BSS	O
machines	O
are	O
more	O
powerful	O
than	O
Turing	B-Architecture
machines	I-Architecture
,	O
because	O
the	O
latter	O
are	O
by	O
definition	O
restricted	O
to	O
a	O
finite	O
alphabet	O
.	O
</s>
<s>
A	O
Turing	B-Architecture
machine	I-Architecture
can	O
be	O
empowered	O
to	O
store	O
arbitrary	O
rational	O
numbers	O
in	O
a	O
single	O
tape	O
symbol	O
by	O
making	O
that	O
finite	O
alphabet	O
arbitrarily	O
large	O
(	O
in	O
terms	O
of	O
a	O
physical	O
machine	O
using	O
transistor-based	O
memory	O
,	O
building	O
its	O
memory	O
locations	O
out	O
of	O
enough	O
transistors	B-Application
to	O
store	O
the	O
desired	O
number	O
)	O
,	O
but	O
this	O
does	O
not	O
extend	O
to	O
the	O
uncountable	O
real	O
numbers	O
(	O
for	O
example	O
,	O
no	O
number	O
of	O
transistors	B-Application
can	O
accurately	O
represent	O
Pi	O
)	O
.	O
</s>
