<s>
In	O
theoretical	O
computer	O
science	O
,	O
a	O
discrete	B-Application
system	I-Application
is	O
a	O
system	O
with	O
a	O
countable	O
number	O
of	O
states	O
.	O
</s>
<s>
Discrete	B-Application
systems	I-Application
may	O
be	O
contrasted	O
with	O
continuous	O
systems	O
,	O
which	O
may	O
also	O
be	O
called	O
analog	O
systems	O
.	O
</s>
<s>
A	O
final	O
discrete	B-Application
system	I-Application
is	O
often	O
modeled	O
with	O
a	O
directed	O
graph	O
and	O
is	O
analyzed	O
for	O
correctness	O
and	O
complexity	O
according	O
to	O
computational	O
theory	O
.	O
</s>
<s>
Because	O
discrete	B-Application
systems	I-Application
have	O
a	O
countable	O
number	O
of	O
states	O
,	O
they	O
may	O
be	O
described	O
in	O
precise	O
mathematical	O
models	O
.	O
</s>
<s>
A	O
computer	O
is	O
a	O
finite-state	B-Architecture
machine	I-Architecture
that	O
may	O
be	O
viewed	O
as	O
a	O
discrete	B-Application
system	I-Application
.	O
</s>
<s>
Because	O
computers	O
are	O
often	O
used	O
to	O
model	O
not	O
only	O
other	O
discrete	B-Application
systems	I-Application
but	O
continuous	O
systems	O
as	O
well	O
,	O
methods	O
have	O
been	O
developed	O
to	O
represent	O
real-world	O
continuous	O
systems	O
as	O
discrete	B-Application
systems	I-Application
.	O
</s>
<s>
One	O
such	O
method	O
involves	O
sampling	B-Algorithm
a	O
continuous	O
signal	O
at	O
discrete	O
time	O
intervals	O
.	O
</s>
