<s>
CPU	B-Algorithm
Sim	I-Algorithm
is	O
a	O
software	B-Application
development	I-Application
environment	I-Application
for	O
the	O
simulation	O
of	O
simple	O
computers	O
.	O
</s>
<s>
It	O
was	O
developed	O
by	O
Dale	O
Skrien	O
to	O
help	O
students	O
understand	O
computer	B-General_Concept
architectures	I-General_Concept
.	O
</s>
<s>
With	O
this	O
application	B-Application
the	O
user	O
is	O
able	O
to	O
simulate	O
new	O
or	O
existing	O
simple	O
CPUs	O
.	O
</s>
<s>
Users	O
can	O
create	O
new	O
virtual	O
CPUs	O
with	O
custom	O
machine	B-Language
language	I-Language
instructions	O
,	O
which	O
are	O
implemented	O
by	O
a	O
sequence	O
of	O
micro	O
instructions	O
.	O
</s>
<s>
CPU	B-Algorithm
Sim	I-Algorithm
allows	O
the	O
user	O
to	O
edit	O
and	O
run	O
assembly	B-Language
language	I-Language
programs	O
for	O
the	O
CPU	O
being	O
simulated	O
.	O
</s>
<s>
CPU	B-Algorithm
Sim	I-Algorithm
has	O
been	O
programmed	O
using	O
the	O
Java	B-Language
Swing	I-Language
package	O
.	O
</s>
<s>
This	O
means	O
that	O
it	O
is	O
platform	B-Operating_System
independent	I-Operating_System
(	O
runs	O
on	O
every	O
platform	O
that	O
has	O
a	O
Java	B-Language
virtual	I-Language
machine	I-Language
installed	O
)	O
.	O
</s>
<s>
A	O
sample	O
computer	O
system	O
,	O
the	O
Wombat	O
1	O
,	O
is	O
provided	O
with	O
CPU	B-Algorithm
Sim	I-Algorithm
.	O
</s>
<s>
pc	O
(	O
program	B-General_Concept
counter	I-General_Concept
)	O
;	O
</s>
<s>
acc	O
(	O
accumulator	B-General_Concept
)	O
;	O
</s>
<s>
ir	O
(	O
instruction	B-General_Concept
register	I-General_Concept
)	O
;	O
</s>
<s>
mar	O
(	O
memory	B-General_Concept
address	I-General_Concept
register	I-General_Concept
)	O
;	O
</s>
<s>
mdr	O
(	O
memory	B-General_Concept
data	I-General_Concept
register	I-General_Concept
)	O
;	O
</s>
<s>
The	O
assembly	B-Language
language	I-Language
of	O
the	O
Wombat	O
1	O
computer	O
consists	O
of	O
12	O
instructions	O
.	O
</s>
<s>
Each	O
instruction	O
is	O
stored	O
on	O
16	O
bits	O
;	O
the	O
first	O
4	O
are	O
the	O
opcode	B-Language
and	O
the	O
other	O
12	O
are	O
the	O
address	O
field	O
.	O
</s>
<s>
CPU	B-Algorithm
Sim	I-Algorithm
has	O
the	O
following	O
features	O
:	O
</s>
<s>
allows	O
the	O
creation	O
of	O
a	O
CPU	O
(	O
a	O
virtual	O
one	O
)	O
,	O
including	O
the	O
registers	O
,	O
RAM	O
,	O
microinstructions	O
,	O
and	O
machine	B-Language
instructions	I-Language
;	O
</s>
<s>
allows	O
the	O
creation	O
,	O
editing	O
,	O
and	O
execution	O
of	O
assembly	B-Language
language	I-Language
programs	O
for	O
the	O
simulated	O
CPU	O
;	O
</s>
<s>
allows	O
stepping	O
forward	O
and	O
backward	O
through	O
the	O
execution	O
of	O
assembly	B-Language
language	I-Language
programs	O
.	O
</s>
