<s>
A	O
one-instruction	B-Application
set	I-Application
computer	I-Application
(	O
OISC	O
)	O
,	O
sometimes	O
called	O
an	O
ultimate	O
reduced	B-Architecture
instruction	I-Architecture
set	I-Architecture
computer	I-Architecture
(	O
URISC	O
)	O
,	O
is	O
an	O
abstract	B-Application
machine	I-Application
that	O
uses	O
only	O
one	O
instructionobviating	O
the	O
need	O
for	O
a	O
machine	B-Language
language	I-Language
opcode	B-Language
.	O
</s>
<s>
With	O
a	O
judicious	O
choice	O
for	O
the	O
single	O
instruction	O
and	O
given	O
infinite	O
resources	O
,	O
an	O
OISC	O
is	O
capable	O
of	O
being	O
a	O
universal	B-Architecture
computer	I-Architecture
in	O
the	O
same	O
manner	O
as	O
traditional	O
computers	O
that	O
have	O
multiple	O
instructions	O
.	O
</s>
<s>
The	O
first	O
carbon	O
nanotube	O
computer	O
is	O
a	O
1-bit	O
one-instruction	B-Application
set	I-Application
computer	I-Application
(	O
and	O
has	O
only	O
178	O
transistors	O
)	O
.	O
</s>
<s>
In	O
a	O
Turing-complete	B-Algorithm
model	I-Algorithm
,	O
each	O
memory	O
location	O
can	O
store	O
an	O
arbitrary	O
integer	O
,	O
anddepending	O
on	O
the	O
modelthere	O
may	O
be	O
arbitrarily	O
many	O
locations	O
.	O
</s>
<s>
There	O
exists	O
a	O
class	O
of	O
universal	B-Architecture
computers	I-Architecture
with	O
a	O
single	O
instruction	O
based	O
on	O
bit	B-Algorithm
manipulation	I-Algorithm
such	O
as	O
bit	O
copying	O
or	O
bit	O
inversion	O
.	O
</s>
<s>
Since	O
their	O
memory	O
model	O
is	O
finite	O
,	O
as	O
is	O
the	O
memory	O
structure	O
used	O
in	O
real	O
computers	O
,	O
those	O
bit	B-Algorithm
manipulation	I-Algorithm
machines	O
are	O
equivalent	O
to	O
real	O
computers	O
rather	O
than	O
to	O
Turing	B-Architecture
machines	I-Architecture
.	O
</s>
<s>
Bit-manipulating	B-Algorithm
machines	O
are	O
the	O
simplest	O
class	O
.	O
</s>
<s>
This	O
process	O
turns	O
out	O
to	O
be	O
capable	O
of	O
universal	B-Architecture
computation	I-Architecture
(	O
i.e.	O
</s>
<s>
The	O
problem	O
of	O
computational	B-Algorithm
universality	I-Algorithm
is	O
solved	O
in	O
this	O
case	O
by	O
keeping	O
predefined	O
jump	O
tables	O
in	O
the	O
memory	O
.	O
</s>
<s>
Transport	B-General_Concept
triggered	I-General_Concept
architecture	I-General_Concept
(	O
TTA	O
)	O
is	O
a	O
design	O
in	O
which	O
computation	O
is	O
a	O
side	O
effect	O
of	O
data	O
transport	O
.	O
</s>
<s>
For	O
example	O
,	O
in	O
an	O
OISC	O
using	O
a	O
single	O
memory-to-memory	O
copy	O
instruction	O
,	O
this	O
is	O
done	O
by	O
triggering	O
ports	O
that	O
perform	O
arithmetic	O
and	O
instruction	B-General_Concept
pointer	I-General_Concept
jumps	O
when	O
written	O
to	O
.	O
</s>
<s>
Arithmetic-based	O
Turing-complete	O
machines	O
use	O
an	O
arithmetic	O
operation	O
and	O
a	O
conditional	B-Language
jump	O
.	O
</s>
<s>
Like	O
the	O
two	O
previous	O
universal	B-Architecture
computers	I-Architecture
,	O
this	O
class	O
is	O
also	O
Turing-complete	O
.	O
</s>
<s>
Hence	O
,	O
there	O
is	O
no	O
need	O
for	O
an	O
opcode	B-Language
to	O
identify	O
which	O
instruction	O
to	O
execute	O
;	O
the	O
choice	O
of	O
instruction	O
is	O
inherent	O
in	O
the	O
design	O
of	O
the	O
machine	O
,	O
and	O
an	O
OISC	O
is	O
typically	O
named	O
after	O
the	O
instruction	O
it	O
uses	O
(	O
e.g.	O
,	O
an	O
SBN	O
OISC	O
,	O
the	O
SUBLEQ	O
language	O
,	O
etc	O
.	O
)	O
.	O
</s>
<s>
However	O
,	O
it	O
is	O
possible	O
to	O
construct	O
Turing	B-Algorithm
complete	I-Algorithm
machines	O
using	O
an	O
instruction	O
based	O
on	O
other	O
arithmetic	O
operations	O
,	O
e.g.	O
,	O
addition	O
.	O
</s>
<s>
The	O
SBNZ	O
a	O
,	O
b	O
,	O
c	B-Language
,	O
d	O
instruction	O
(	O
"	O
subtract	O
and	O
branch	O
if	O
not	O
equal	O
to	O
zero	O
"	O
)	O
subtracts	O
the	O
contents	O
at	O
address	O
a	O
from	O
the	O
contents	O
at	O
address	O
b	O
,	O
stores	O
the	O
result	O
at	O
address	O
c	B-Language
,	O
and	O
then	O
,	O
if	O
the	O
result	O
is	O
not	O
0	O
,	O
transfers	O
control	O
to	O
address	O
d	O
(	O
if	O
the	O
result	O
is	O
equal	O
to	O
zero	O
,	O
execution	O
proceeds	O
to	O
the	O
next	B-General_Concept
instruction	I-General_Concept
in	O
sequence	O
)	O
.	O
</s>
<s>
The	O
instruction	O
(	O
"	O
subtract	O
and	O
branch	O
if	O
less	O
than	O
or	O
equal	O
to	O
zero	O
"	O
)	O
subtracts	O
the	O
contents	O
at	O
address	O
from	O
the	O
contents	O
at	O
address	O
,	O
stores	O
the	O
result	O
at	O
address	O
,	O
and	O
then	O
,	O
if	O
the	O
result	O
is	O
not	O
positive	O
,	O
transfers	O
control	O
to	O
address	O
(	O
if	O
the	O
result	O
is	O
positive	O
,	O
execution	O
proceeds	O
to	O
the	O
next	B-General_Concept
instruction	I-General_Concept
in	O
sequence	O
)	O
.	O
</s>
<s>
Pseudocode	B-Language
:	O
</s>
<s>
Conditional	B-Language
branching	I-Language
can	O
be	O
suppressed	O
by	O
setting	O
the	O
third	O
operand	O
equal	O
to	O
the	O
address	O
of	O
the	O
next	B-General_Concept
instruction	I-General_Concept
in	O
sequence	O
.	O
</s>
<s>
A	O
variant	O
is	O
also	O
possible	O
with	O
two	O
operands	O
and	O
an	O
internal	O
accumulator	B-General_Concept
,	O
where	O
the	O
accumulator	B-General_Concept
is	O
subtracted	O
from	O
the	O
memory	O
location	O
specified	O
by	O
the	O
first	O
operand	O
.	O
</s>
<s>
The	O
result	O
is	O
stored	O
in	O
both	O
the	O
accumulator	B-General_Concept
and	O
the	O
memory	O
location	O
,	O
and	O
the	O
second	O
operand	O
specifies	O
the	O
branch	O
address	O
:	O
</s>
<s>
Addition	O
can	O
be	O
performed	O
by	O
repeated	O
subtraction	O
,	O
with	O
no	O
conditional	B-Language
branching	I-Language
;	O
e.g.	O
,	O
the	O
following	O
instructions	O
result	O
in	O
the	O
content	O
at	O
location	O
being	O
added	O
to	O
the	O
content	O
at	O
location	O
:	O
</s>
<s>
The	O
following	O
program	O
(	O
written	O
in	O
pseudocode	B-Language
)	O
emulates	O
the	O
execution	O
of	O
a	O
-based	O
OISC	O
:	O
</s>
<s>
Similar	O
interpreters	O
written	O
in	O
a	O
-based	O
language	O
(	O
i.e.	O
,	O
self-interpreters	O
,	O
which	O
may	O
use	O
self-modifying	B-Application
code	I-Application
as	O
allowed	O
by	O
the	O
nature	O
of	O
the	O
instruction	O
)	O
can	O
be	O
found	O
in	O
the	O
external	O
links	O
below	O
.	O
</s>
<s>
A	O
general	O
purpose	O
SMP-capable	O
64-bit	O
operating	B-General_Concept
system	I-General_Concept
called	O
Dawn	O
OS	O
has	O
been	O
implemented	O
in	O
an	O
emulated	O
Subleq	O
machine	O
.	O
</s>
<s>
The	O
OS	O
contains	O
a	O
C-like	O
compiler	B-Language
.	O
</s>
<s>
There	O
is	O
a	O
compiler	B-Language
called	O
Higher	O
Subleq	O
written	O
by	O
Oleg	O
Mazonka	O
that	O
compiles	B-Language
a	O
simplified	O
C	B-Language
program	I-Language
into	O
code	O
.	O
</s>
<s>
Conditional	B-Language
branching	I-Language
can	O
be	O
suppressed	O
by	O
setting	O
the	O
third	O
operand	O
equal	O
to	O
the	O
address	O
of	O
the	O
next	B-General_Concept
instruction	I-General_Concept
in	O
sequence	O
.	O
</s>
<s>
In	O
an	O
attempt	O
to	O
make	O
Turing	B-Architecture
machine	I-Architecture
more	O
intuitive	O
,	O
Z	O
.	O
</s>
<s>
Pseudocode	B-Language
:	O
</s>
<s>
After	O
giving	O
a	O
few	O
programs	O
:	O
multiplication	O
,	O
gcd	O
,	O
computing	O
the	O
n-th	O
prime	O
number	O
,	O
representation	O
in	O
base	O
b	O
of	O
an	O
arbitrary	O
number	O
,	O
sorting	O
in	O
order	O
of	O
magnitude	O
,	O
Melzak	O
shows	O
explicitly	O
how	O
to	O
simulate	O
an	O
arbitrary	O
Turing	B-Architecture
machine	I-Architecture
on	O
his	O
arithmetic	O
machine	O
.	O
</s>
<s>
In	O
a	O
reverse	O
subtract	O
and	O
skip	O
if	O
borrow	O
(	O
RSSB	O
)	O
instruction	O
,	O
the	O
accumulator	B-General_Concept
is	O
subtracted	O
from	O
the	O
memory	O
location	O
and	O
the	O
next	B-General_Concept
instruction	I-General_Concept
is	O
skipped	O
if	O
there	O
was	O
a	O
borrow	O
(	O
memory	O
location	O
was	O
smaller	O
than	O
the	O
accumulator	B-General_Concept
)	O
.	O
</s>
<s>
The	O
result	O
is	O
stored	O
in	O
both	O
the	O
accumulator	B-General_Concept
and	O
the	O
memory	O
location	O
.	O
</s>
<s>
The	O
program	B-General_Concept
counter	I-General_Concept
is	O
mapped	O
to	O
memory	O
location	O
0	O
.	O
</s>
<s>
The	O
accumulator	B-General_Concept
is	O
mapped	O
to	O
memory	O
location	O
1	O
.	O
</s>
<s>
A	O
transport	B-General_Concept
triggered	I-General_Concept
architecture	I-General_Concept
uses	O
only	O
the	O
move	O
instruction	O
,	O
hence	O
it	O
was	O
originally	O
called	O
a	O
"	O
move	O
machine	O
"	O
.	O
</s>
<s>
So	O
memory	O
cells	O
are	O
not	O
simple	O
store	O
but	O
coupled	O
with	O
an	O
arithmetic	B-General_Concept
logic	I-General_Concept
unit	I-General_Concept
(	O
ALU	O
)	O
setup	O
to	O
perform	O
only	O
one	O
sort	O
of	O
operation	O
with	O
the	O
current	O
value	O
of	O
the	O
cell	O
.	O
</s>
<s>
Some	O
of	O
the	O
cells	O
are	O
control	O
flow	O
instructions	O
to	O
alter	O
the	O
program	O
execution	O
with	O
jumps	O
,	O
conditional	B-Language
execution	O
,	O
subroutines	O
,	O
if-then-else	B-Language
,	O
for-loop	B-Language
,	O
etc	O
...	O
</s>
<s>
A	O
commercial	O
transport	B-General_Concept
triggered	I-General_Concept
architecture	I-General_Concept
microcontroller	O
has	O
been	O
produced	O
called	O
MAXQ	O
,	O
which	O
hides	O
the	O
apparent	O
inconvenience	O
of	O
an	O
OISC	O
by	O
using	O
a	O
"	O
transfer	O
map	O
"	O
that	O
represents	O
all	O
possible	O
destinations	O
for	O
the	O
move	O
instructions	O
.	O
</s>
<s>
Cryptoleq	O
works	O
on	O
continuous	O
cells	O
of	O
memory	O
using	O
direct	O
and	O
indirect	O
addressing	O
,	O
and	O
performs	O
two	O
operations	O
and	O
on	O
three	O
values	O
A	O
,	O
B	O
,	O
and	O
C	B-Language
:	O
</s>
<s>
where	O
a	O
,	O
b	O
and	O
c	B-Language
are	O
addressed	O
by	O
the	O
instruction	B-General_Concept
pointer	I-General_Concept
,	O
IP	O
,	O
with	O
the	O
value	O
of	O
IP	O
addressing	O
a	O
,	O
IP	O
+	O
1	O
point	O
to	O
b	O
and	O
IP	O
+	O
2	O
to	O
c	B-Language
.	O
</s>
<s>
The	O
multiplication	O
algorithm	O
is	O
based	O
on	O
addition	O
and	O
subtraction	O
,	O
uses	O
the	O
function	O
G	O
and	O
does	O
not	O
have	O
conditional	B-Language
jumps	O
nor	O
branches	O
.	O
</s>
<s>
Cryptoleq	O
encryption	O
is	O
based	O
on	O
Paillier	B-Algorithm
cryptosystem	I-Algorithm
.	O
</s>
