<s>
CARDIAC	O
(	O
CARDboard	B-Application
Illustrative	I-Application
Aid	I-Application
to	I-Application
Computation	I-Application
)	O
is	O
a	O
learning	O
aid	O
developed	O
by	O
David	O
Hagelbarger	O
and	O
Saul	O
Fingerman	O
for	O
Bell	O
Telephone	O
Laboratories	O
in	O
1968	O
to	O
teach	O
high	O
school	O
students	O
how	O
computers	O
work	O
.	O
</s>
<s>
The	O
computer	O
operates	O
in	O
base	B-Application
10	I-Application
and	O
has	O
100	O
memory	B-Algorithm
cells	I-Algorithm
which	O
can	O
hold	O
signed	O
numbers	O
from	O
0	O
to	O
±999	O
.	O
</s>
<s>
The	O
“	O
CPU	B-General_Concept
”	O
of	O
the	O
computer	O
consists	O
of	O
4	O
slides	O
that	O
move	O
various	O
numbers	O
and	O
arrows	O
to	O
have	O
the	O
flow	O
of	O
the	O
real	O
CPU	B-General_Concept
(	O
the	O
user	O
's	O
brain	O
)	O
move	O
the	O
right	O
way	O
.	O
</s>
<s>
Memory	B-General_Concept
consists	O
of	O
the	O
other	O
half	O
of	O
the	O
cardboard	O
cutout	O
.	O
</s>
<s>
Cell	O
0	O
is	O
“	O
ROM	B-Device
”	O
,	O
always	O
containing	O
a	O
numeric	O
"	O
1	O
"	O
;	O
cells	O
1	O
to	O
98	O
are	O
“	O
RAM	B-Architecture
”	O
;	O
available	O
for	O
instructions	O
and	O
data	O
;	O
and	O
cell	O
99	O
can	O
best	O
be	O
described	O
as	O
“	O
EEPROM	B-General_Concept
”	O
.	O
</s>
<s>
Memory	B-Algorithm
cells	I-Algorithm
hold	O
signed	O
decimal	B-Application
numbers	O
from	O
0	O
to	O
±999	O
and	O
are	O
written	O
with	O
a	O
pencil	O
.	O
</s>
<s>
A	O
“	O
bug	O
”	O
is	O
provided	O
to	O
act	O
as	O
a	O
program	O
counter	O
,	O
and	O
is	O
placed	O
in	O
a	O
hole	O
beside	O
the	O
current	O
memory	B-Algorithm
cell	I-Algorithm
.	O
</s>
<s>
CARDIAC	O
has	O
a	O
10	O
instruction	O
machine	B-Language
language	I-Language
.	O
</s>
<s>
An	O
instruction	O
is	O
three	O
decimal	B-Application
digits	O
(	O
the	O
sign	O
is	O
ignored	O
)	O
in	O
the	O
form	O
OAA	O
.	O
</s>
<s>
Addressing	O
is	O
one	O
of	O
accumulator	O
to	O
memory	B-General_Concept
absolute	O
,	O
absolute	O
memory	B-General_Concept
to	O
accumulator	O
,	O
input	O
to	O
absolute	O
memory	B-General_Concept
and	O
absolute	O
memory	B-General_Concept
to	O
output	O
.	O
</s>
<s>
Programs	O
are	O
hand	O
assembled	O
and	O
then	O
are	O
penciled	O
into	O
the	O
appropriate	O
memory	B-Algorithm
cells	I-Algorithm
.	O
</s>
<s>
+	O
CARDIAC	O
Instruction	O
Set	O
Opcode	O
Mnemonic	O
Instruction	O
Description	O
0	O
INP	O
Input	O
take	O
a	O
number	O
from	O
the	O
input	O
card	O
and	O
put	O
it	O
in	O
a	O
specified	O
memory	B-Algorithm
cell	I-Algorithm
.	O
</s>
<s>
1	O
CLA	O
Clear	O
and	O
add	O
clear	O
the	O
accumulator	O
and	O
add	O
the	O
contents	O
of	O
a	O
memory	B-Algorithm
cell	I-Algorithm
to	O
the	O
accumulator	O
.	O
</s>
<s>
2	O
ADD	O
Add	O
add	O
the	O
contents	O
of	O
a	O
memory	B-Algorithm
cell	I-Algorithm
to	O
the	O
accumulator	O
.	O
</s>
<s>
3	O
TAC	O
Test	O
accumulator	O
contents	O
performs	O
a	O
sign	O
test	O
on	O
the	O
contents	O
of	O
the	O
accumulator	O
;	O
if	O
minus	O
,	O
jump	O
to	O
a	O
specified	O
memory	B-Algorithm
cell	I-Algorithm
.	O
</s>
<s>
5	O
OUT	O
Output	O
take	O
a	O
number	O
from	O
the	O
specified	O
memory	B-Algorithm
cell	I-Algorithm
and	O
write	O
it	O
on	O
the	O
output	O
card	O
.	O
</s>
<s>
6	O
STO	O
Store	O
copy	O
the	O
contents	O
of	O
the	O
accumulator	O
into	O
a	O
specified	O
memory	B-Algorithm
cell	I-Algorithm
.	O
</s>
<s>
7	O
SUB	O
Subtract	O
subtract	O
the	O
contents	O
of	O
a	O
specified	O
memory	B-Algorithm
cell	I-Algorithm
from	O
the	O
accumulator	O
.	O
</s>
<s>
8	O
JMP	O
Jump	O
jump	O
to	O
a	O
specified	O
memory	B-Algorithm
cell	I-Algorithm
.	O
</s>
<s>
Programs	O
are	O
run	O
by	O
first	O
sliding	O
three	O
slides	O
so	O
that	O
the	O
number	O
in	O
the	O
instruction	O
register	O
equals	O
the	O
number	O
in	O
the	O
memory	B-Algorithm
cell	I-Algorithm
the	O
bug	O
is	O
sitting	O
in	O
.	O
</s>
<s>
Once	O
that	O
is	O
done	O
the	O
bug	O
is	O
moved	O
to	O
the	O
next	O
memory	B-Algorithm
cell	I-Algorithm
.	O
</s>
