<s>
In	O
computer	B-General_Concept
science	I-General_Concept
,	O
a	O
tagged	B-Architecture
architecture	I-Architecture
is	O
a	O
particular	O
type	O
of	O
computer	B-General_Concept
architecture	I-General_Concept
where	O
every	O
word	O
of	O
memory	O
constitutes	O
a	O
tagged	B-Language
union	I-Language
,	O
being	O
divided	O
into	O
a	O
number	O
of	O
bits	O
of	O
data	O
,	O
and	O
a	O
tag	O
section	O
that	O
describes	O
the	O
type	O
of	O
the	O
data	O
:	O
how	O
it	O
is	O
to	O
be	O
interpreted	O
,	O
and	O
,	O
if	O
it	O
is	O
a	O
reference	O
,	O
the	O
type	O
of	O
the	O
object	O
that	O
it	O
points	O
to	O
.	O
</s>
<s>
In	O
contrast	O
,	O
program	O
and	O
data	O
memory	O
are	O
indistinguishable	O
in	O
the	O
von	B-Architecture
Neumann	I-Architecture
architecture	I-Architecture
,	O
making	O
the	O
way	O
the	O
memory	O
is	O
referenced	O
critical	O
to	O
interpret	O
the	O
correct	O
meaning	O
.	O
</s>
<s>
Notable	O
examples	O
of	O
American	O
tagged	B-Architecture
architectures	I-Architecture
were	O
the	O
Lisp	B-Operating_System
machines	I-Operating_System
,	O
which	O
had	O
tagged	O
pointer	O
support	O
at	O
the	O
hardware	O
and	O
opcode	B-Language
level	O
,	O
the	O
Burroughs	B-Device
large	I-Device
systems	I-Device
,	O
which	O
have	O
a	O
data-driven	O
tagged	O
and	O
descriptor-based	O
architecture	O
,	O
and	O
the	O
non-commercial	O
Rice	B-Device
Computer	I-Device
.	O
</s>
<s>
Both	O
the	O
Burroughs	O
and	O
Lisp	B-Operating_System
machine	I-Operating_System
are	O
examples	O
of	O
high-level	B-Architecture
language	I-Architecture
computer	I-Architecture
architectures	I-Architecture
,	O
where	O
the	O
tagging	O
is	O
used	O
to	O
support	O
types	O
from	O
a	O
high-level	B-Language
language	I-Language
at	O
the	O
hardware	O
level	O
.	O
</s>
<s>
In	O
addition	O
to	O
this	O
,	O
the	O
original	O
Xerox	B-Application
Smalltalk	I-Application
implementation	O
used	O
the	O
least-significant	O
bit	O
of	O
each	O
16-bit	O
word	O
as	O
a	O
tag	O
bit	O
:	O
if	O
it	O
was	O
clear	O
then	O
the	O
hardware	O
would	O
accept	O
it	O
as	O
an	O
aligned	B-Application
memory	O
address	O
while	O
if	O
it	O
was	O
set	O
it	O
was	O
treated	O
as	O
a	O
(	O
shifted	O
)	O
15-bit	O
integer	O
.	O
</s>
<s>
In	O
the	O
Soviet	O
Union	O
,	O
the	O
Elbrus	B-Device
series	O
of	O
supercomputers	O
pioneered	O
the	O
use	O
of	O
tagged	B-Architecture
architectures	I-Architecture
in	O
1973	O
.	O
</s>
