<s>
16-bit	B-Device
microcomputers	B-Architecture
are	O
microcomputers	B-Architecture
that	O
use	O
16-bit	B-Device
microprocessors	B-Architecture
.	O
</s>
<s>
A	O
16-bit	B-Device
register	O
can	O
store	O
216	O
different	O
values	O
.	O
</s>
<s>
The	O
range	B-Data_Structure
of	O
integer	O
values	O
that	O
can	O
be	O
stored	O
in	O
16	B-Device
bits	I-Device
depends	O
on	O
the	O
integer	O
representation	O
used	O
.	O
</s>
<s>
With	O
the	O
two	O
most	O
common	O
representations	O
,	O
the	O
range	B-Data_Structure
is	O
0	O
through	O
65,535	O
(	O
216	O
−	O
1	O
)	O
for	O
representation	O
as	O
an	O
(	O
unsigned	B-Algorithm
)	O
binary	O
number	O
,	O
and	O
−	O
32,768	O
( −1	O
×	O
215	O
)	O
through	O
32,767	O
(	O
215	O
−	O
1	O
)	O
for	O
representation	O
as	O
two	B-General_Concept
's	I-General_Concept
complement	I-General_Concept
.	O
</s>
<s>
Since	O
216	O
is	O
65	O
,	O
536	O
,	O
a	O
processor	O
with	O
16-bit	B-Device
memory	O
addresses	O
can	O
directly	O
access	O
64	O
KB	O
(	O
65,536	O
bytes	B-Application
)	O
of	O
byte-addressable	B-General_Concept
memory	O
.	O
</s>
<s>
If	O
a	O
system	O
uses	O
segmentation	B-General_Concept
with	O
16-bit	B-Device
segment	O
offsets	O
,	O
more	O
can	O
be	O
accessed	O
.	O
</s>
<s>
The	O
MIT	B-Device
Whirlwind	I-Device
(	O
1951	O
)	O
was	O
quite	O
possibly	O
the	O
first-ever	O
16-bit	B-Device
computer	I-Device
.	O
</s>
<s>
This	O
changed	O
with	O
the	O
effort	O
to	O
introduce	O
ASCII	B-Protocol
,	O
which	O
used	O
a	O
7-bit	O
code	O
and	O
naturally	O
led	O
to	O
the	O
use	O
of	O
an	O
8-bit	O
multiple	O
which	O
could	O
store	O
a	O
single	O
ASCII	B-Protocol
character	I-Protocol
or	O
two	O
binary	O
coded	O
decimal	O
digits	O
.	O
</s>
<s>
The	O
16-bit	B-Device
word	O
length	O
thus	O
became	O
more	O
common	O
in	O
the	O
1960s	O
,	O
especially	O
on	O
minicomputer	O
systems	O
.	O
</s>
<s>
Early	O
16-bit	B-Device
computers	I-Device
(	O
1965	O
–	O
70	O
)	O
include	O
the	O
IBM	B-Device
1130	I-Device
,	O
the	O
HP	B-Device
2100	I-Device
,	O
the	O
Data	B-Device
General	I-Device
Nova	I-Device
,	O
and	O
the	O
DEC	B-Device
PDP-11	I-Device
.	O
</s>
<s>
Early	O
16-bit	B-Device
microprocessors	B-Architecture
,	O
often	O
modeled	O
on	O
one	O
of	O
the	O
mini	O
platforms	O
,	O
began	O
to	O
appear	O
in	O
the	O
1970s	O
.	O
</s>
<s>
Examples	O
(	O
1973	O
–	O
76	O
)	O
include	O
the	O
five-chip	O
National	B-Device
Semiconductor	I-Device
IMP-16	I-Device
(	O
1973	O
)	O
,	O
the	O
two-chip	O
NEC	O
μCOM-16	O
(	O
1974	O
)	O
,	O
the	O
three-chip	O
Western	B-General_Concept
Digital	I-General_Concept
MCP-1600	I-General_Concept
(	O
1975	O
)	O
,	O
and	O
the	O
five-chip	O
Toshiba	O
T-3412	O
(	O
1976	O
)	O
.	O
</s>
<s>
Early	O
single-chip	O
16-bit	B-Device
microprocessors	B-Architecture
(	O
1975	O
–	O
76	O
)	O
include	O
the	O
Panafacom	B-General_Concept
MN1610	I-General_Concept
(	O
1975	O
)	O
,	O
National	B-Device
Semiconductor	I-Device
PACE	I-Device
(	O
1975	O
)	O
,	O
General	O
Instrument	O
CP1600	O
(	O
1975	O
)	O
,	O
Texas	B-General_Concept
Instruments	I-General_Concept
TMS9900	I-General_Concept
(	O
1976	O
)	O
,	O
Ferranti	B-General_Concept
F100-L	I-General_Concept
,	O
and	O
the	O
HP	O
BPC	O
.	O
</s>
<s>
Other	O
notable	O
16-bit	B-Device
processors	I-Device
include	O
the	O
Intel	B-General_Concept
8086	I-General_Concept
,	O
the	O
Intel	B-General_Concept
80286	I-General_Concept
,	O
the	O
WDC	B-General_Concept
65C816	I-General_Concept
,	O
and	O
the	O
Zilog	B-Device
Z8000	I-Device
.	O
</s>
<s>
The	O
Intel	B-Device
8088	I-Device
was	O
binary	B-General_Concept
compatible	I-General_Concept
with	O
the	O
Intel	B-General_Concept
8086	I-General_Concept
,	O
and	O
was	O
16-bit	B-Device
in	O
that	O
its	O
registers	O
were	O
16	B-Device
bits	I-Device
wide	O
,	O
and	O
arithmetic	O
instructions	O
could	O
operate	O
on	O
16-bit	B-Device
quantities	O
,	O
even	O
though	O
its	O
external	O
bus	O
was	O
8bits	O
wide	O
.	O
</s>
<s>
A	O
16-bit	B-Device
integer	O
can	O
store	O
216	O
(	O
or	O
65,536	O
)	O
distinct	O
values	O
.	O
</s>
<s>
In	O
an	O
unsigned	B-Algorithm
representation	O
,	O
these	O
values	O
are	O
the	O
integers	O
between	O
0	O
and	O
65,535	O
;	O
using	O
two	B-General_Concept
's	I-General_Concept
complement	I-General_Concept
,	O
possible	O
values	O
range	B-Data_Structure
from	O
−	O
32,768	O
to	O
32,767	O
.	O
</s>
<s>
Hence	O
,	O
a	O
processor	O
with	O
16-bit	B-Device
memory	O
addresses	O
can	O
directly	O
access	O
64KB	O
of	O
byte-addressable	B-General_Concept
memory	O
.	O
</s>
<s>
16-bit	B-Device
processors	I-Device
have	O
been	O
almost	O
entirely	O
supplanted	O
in	O
the	O
personal	B-Device
computer	I-Device
industry	O
,	O
and	O
are	O
used	O
less	O
than	O
32-bit	O
(	O
or	O
8-bit	O
)	O
CPUs	O
in	O
embedded	O
applications	O
.	O
</s>
<s>
The	O
Motorola	B-Device
68000	I-Device
is	O
sometimes	O
called	O
16-bit	B-Device
because	O
of	O
the	O
way	O
it	O
handles	O
basic	O
arithmetic	O
.	O
</s>
<s>
The	O
instruction	O
set	O
was	O
based	O
on	O
32-bit	O
numbers	O
and	O
the	O
internal	O
registers	O
were	O
32bits	O
wide	O
,	O
so	O
by	O
common	O
definitions	O
,	O
the	O
68000	B-Device
is	O
a	O
32-bit	O
design	O
.	O
</s>
<s>
Internally	O
,	O
32-bit	O
arithmetic	O
is	O
performed	O
using	O
two	O
16-bit	B-Device
operations	O
,	O
and	O
this	O
leads	O
to	O
some	O
descriptions	O
of	O
the	O
system	O
as	O
16-bit	B-Device
,	O
or	O
"	O
16/32	O
"	O
.	O
</s>
<s>
A	O
common	O
example	O
is	O
the	O
Data	B-Device
General	I-Device
Nova	I-Device
,	O
which	O
was	O
a	O
16-bit	B-Device
design	O
that	O
performed	O
16-bit	B-Device
math	O
as	O
a	O
series	O
of	O
four	O
4-bit	O
operations	O
.	O
</s>
<s>
4-bits	O
was	O
the	O
word	O
size	O
of	O
a	O
widely	O
available	O
single-chip	O
ALU	B-General_Concept
and	O
thus	O
allowed	O
for	O
inexpensive	O
implementation	O
.	O
</s>
<s>
Using	O
the	O
definition	O
being	O
applied	O
to	O
the	O
68000	B-Device
,	O
the	O
Nova	B-Device
would	O
be	O
a	O
4-bit	O
computer	O
,	O
or	O
4/16	O
.	O
</s>
<s>
Not	O
long	O
after	O
the	O
introduction	O
of	O
the	O
Nova	B-Device
a	O
second	O
version	O
was	O
introduced	O
,	O
the	O
SuperNova	O
,	O
which	O
included	O
four	O
of	O
the	O
4-bit	O
ALUs	O
running	O
in	O
parallel	O
to	O
perform	O
math	O
16bits	O
at	O
a	O
time	O
and	O
therefore	O
offer	O
higher	O
performance	O
.	O
</s>
<s>
This	O
was	O
invisible	O
to	O
the	O
user	O
and	O
the	O
programs	O
,	O
which	O
always	O
used	O
16-bit	B-Device
instructions	O
and	O
data	O
.	O
</s>
<s>
In	O
a	O
similar	O
fashion	O
,	O
later	O
68000-family	O
members	O
,	O
like	O
the	O
Motorola	B-Device
68020	I-Device
,	O
had	O
32-bit	O
ALUs	O
.	O
</s>
<s>
One	O
may	O
also	O
see	O
references	O
to	O
systems	O
being	O
,	O
or	O
not	O
being	O
,	O
16-bit	B-Device
based	O
on	O
some	O
other	O
measure	O
.	O
</s>
<s>
Most	O
8-bit	O
CPUs	O
of	O
the	O
1970s	O
fall	O
into	O
this	O
category	O
;	O
the	O
MOS	B-General_Concept
6502	I-General_Concept
,	O
Intel	B-General_Concept
8080	I-General_Concept
,	O
Zilog	B-General_Concept
Z80	I-General_Concept
and	O
most	O
others	O
had	O
16-bit	B-Device
address	O
space	O
which	O
provided	O
64KB	O
of	O
address	O
space	O
.	O
</s>
<s>
For	O
this	O
reason	O
,	O
most	O
processors	O
had	O
special	O
8-bit	O
addressing	O
modes	O
,	O
the	O
zero	B-General_Concept
page	I-General_Concept
,	O
improving	O
speed	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
68000	B-Device
exposed	O
only	O
24	O
bits	O
of	O
addressing	O
on	O
the	O
DIP	B-Algorithm
,	O
limiting	O
it	O
to	O
a	O
still	O
huge	O
(	O
for	O
the	O
era	O
)	O
16MB	O
.	O
</s>
<s>
A	O
similar	O
analysis	O
applies	O
to	O
Intel	O
's	O
80286	B-General_Concept
CPU	O
replacement	O
,	O
called	O
the	O
386SX	B-General_Concept
,	O
which	O
is	O
a	O
32-bit	O
processor	O
with	O
32-bit	O
ALU	B-General_Concept
and	O
internal	O
32-bit	O
data	O
paths	O
with	O
a	O
16-bit	B-Device
external	O
bus	O
and	O
24-bit	O
addressing	O
of	O
the	O
processor	O
it	O
replaced	O
.	O
</s>
<s>
In	O
the	O
context	O
of	O
IBM	O
PC	O
compatible	O
and	O
Wintel	B-Device
platforms	O
,	O
a	O
16-bit	B-Device
application	O
is	O
any	O
software	O
written	O
for	O
MS-DOS	B-Application
,	O
OS/2	B-Application
1.x	O
or	O
early	O
versions	O
of	O
Microsoft	B-Application
Windows	I-Application
which	O
originally	O
ran	O
on	O
the	O
16-bit	B-Device
Intel	B-Device
8088	I-Device
and	O
Intel	B-General_Concept
80286	I-General_Concept
microprocessors	B-Architecture
.	O
</s>
<s>
Such	O
applications	O
used	O
a	O
20-bit	O
or	O
24-bit	O
segment	B-Device
or	I-Device
selector-offset	I-Device
address	O
representation	O
to	O
extend	O
the	O
range	B-Data_Structure
of	O
addressable	O
memory	B-General_Concept
locations	I-General_Concept
beyond	O
what	O
was	O
possible	O
using	O
only	O
16-bit	B-Device
addresses	O
.	O
</s>
<s>
Programs	O
containing	O
more	O
than	O
216	O
bytes	B-Application
(	O
65,536	O
bytes	B-Application
)	O
of	O
instructions	O
and	O
data	O
therefore	O
required	O
special	O
instructions	O
to	O
switch	O
between	O
their	O
64-kilobyte	O
segments	B-General_Concept
,	O
increasing	O
the	O
complexity	O
of	O
programming	O
16-bit	B-Device
applications	O
.	O
</s>
