<s>
Byte	B-General_Concept
addressing	I-General_Concept
in	O
hardware	O
architectures	O
supports	O
accessing	O
individual	O
bytes	B-Application
.	O
</s>
<s>
Computers	O
with	O
byte	B-General_Concept
addressing	I-General_Concept
are	O
sometimes	O
called	O
byte	B-General_Concept
machines	I-General_Concept
,	O
in	O
contrast	O
to	O
word-addressable	B-General_Concept
architectures	O
,	O
word	O
machines	O
,	O
that	O
access	O
data	O
by	O
word	O
.	O
</s>
<s>
For	O
example	O
,	O
32-bit	O
x86	B-Operating_System
processors	O
have	O
32-bit	O
general-purpose	O
registers	O
and	O
can	O
handle	O
32-bit	O
(	O
4-byte	O
)	O
data	O
in	O
single	O
instructions	O
.	O
</s>
<s>
Instruction	O
sets	O
that	O
support	O
byte	B-General_Concept
addressing	I-General_Concept
supports	O
accessing	O
data	O
in	O
units	O
that	O
are	O
narrower	O
than	O
the	O
word	O
length	O
.	O
</s>
<s>
An	O
eight-bit	O
processor	O
like	O
the	O
Intel	B-General_Concept
8008	I-General_Concept
addresses	O
eight	O
bits	O
,	O
but	O
as	O
this	O
is	O
the	O
full	O
width	O
of	O
the	O
accumulator	O
and	O
other	O
registers	O
,	O
this	O
is	O
could	O
be	O
considered	O
either	O
byte-addressable	B-General_Concept
or	O
word-addressable	B-General_Concept
.	O
</s>
<s>
32-bit	O
x86	B-Operating_System
processors	O
,	O
which	O
address	O
memory	O
in	O
8-bit	O
units	O
but	O
have	O
32-bit	O
general-purpose	O
registers	O
and	O
can	O
operate	O
on	O
32-bit	O
items	O
with	O
a	O
single	O
instruction	O
,	O
are	O
byte-addressable	B-General_Concept
.	O
</s>
<s>
The	O
advantage	O
of	O
word	B-General_Concept
addressing	I-General_Concept
is	O
that	O
more	O
memory	O
can	O
be	O
addressed	O
in	O
the	O
same	O
number	O
of	O
bits	O
.	O
</s>
<s>
The	O
IBM	B-Device
7094	I-Device
has	O
15-bit	O
addresses	O
,	O
so	O
could	O
address	O
32,768	O
words	O
of	O
36	O
bits	O
.	O
</s>
<s>
Addressing	O
32,768	O
bytes	B-Application
of	O
6	O
bits	O
would	O
have	O
been	O
much	O
less	O
useful	O
for	O
scientific	O
and	O
engineering	O
users	O
.	O
</s>
<s>
Or	O
consider	O
32-bit	O
x86	B-Operating_System
processors	O
.	O
</s>
<s>
Using	O
word	B-General_Concept
addressing	I-General_Concept
,	O
a	O
32-bit	O
processor	O
could	O
address	O
4	O
Gigawords	O
;	O
or	O
16	O
Gigabytes	O
using	O
the	O
modern	O
8-bit	O
byte	B-Application
.	O
</s>
<s>
If	O
the	O
386	O
and	O
its	O
successors	O
had	O
used	O
word	B-General_Concept
addressing	I-General_Concept
,	O
scientists	O
,	O
engineers	O
,	O
and	O
gamers	O
could	O
all	O
have	O
run	O
programs	O
that	O
were	O
4x	O
larger	O
on	O
32-bit	O
machines	O
.	O
</s>
<s>
When	O
computers	O
were	O
so	O
costly	O
that	O
they	O
were	O
only	O
or	O
mainly	O
used	O
for	O
science	O
and	O
engineering	O
,	O
word	B-General_Concept
addressing	I-General_Concept
was	O
the	O
obvious	O
mode	O
.	O
</s>
<s>
As	O
it	O
became	O
cost-effective	O
to	O
use	O
computers	O
for	O
handling	O
text	O
,	O
hardware	O
designers	O
moved	O
to	O
byte	B-General_Concept
addressing	I-General_Concept
.	O
</s>
<s>
To	O
illustrate	O
why	O
byte	B-General_Concept
addressing	I-General_Concept
is	O
useful	O
,	O
consider	O
the	O
IBM	B-Device
7094	I-Device
,	O
which	O
is	O
word-addressable	B-General_Concept
and	O
has	O
no	O
concept	O
of	O
a	O
byte	B-Application
.	O
</s>
<s>
With	O
byte	B-General_Concept
addressing	I-General_Concept
,	O
that	O
can	O
be	O
achieved	O
in	O
one	O
instruction	O
:	O
store	O
this	O
character	O
code	O
at	O
that	O
byte	B-General_Concept
address	I-General_Concept
.	O
</s>
<s>
Some	O
systems	O
with	O
word	B-General_Concept
addressing	I-General_Concept
,	O
such	O
as	O
the	O
PDP-6/10	B-Device
and	O
the	O
GE-600/Honeywell	O
6000	O
series	O
,	O
have	O
special	O
mechanisms	O
for	O
accessing	O
bytes	B-Application
efficiently	O
.	O
</s>
<s>
On	O
the	O
PDP-6/10	B-Device
,	O
special	O
instructions	O
operated	O
on	O
a	O
byte	B-Application
pointer	O
which	O
included	O
a	O
word	B-General_Concept
address	I-General_Concept
,	O
a	O
bit	O
offset	O
,	O
and	O
a	O
bit	O
width	O
.	O
</s>
<s>
The	O
/	O
instructions	O
loaded	O
or	O
stored	O
one	O
byte	B-Application
,	O
the	O
instruction	O
incremented	O
the	O
byte	B-Application
pointer	O
,	O
and	O
the	O
/	O
instructions	O
incremented	O
the	O
byte	B-Application
pointer	O
and	O
then	O
loaded	O
or	O
stored	O
the	O
next	O
byte	B-Application
.	O
</s>
<s>
Programs	O
took	O
advantage	O
of	O
this	O
flexibility	O
:	O
those	O
not	O
needing	O
lowercase	O
letters	O
used	O
the	O
limited	O
character	O
set	O
of	O
6-bit	O
bytes	B-Application
for	O
efficiency	O
;	O
most	O
used	O
7-bit	B-Protocol
ASCII	I-Protocol
,	O
packed	O
5	O
to	O
a	O
word	O
with	O
one	O
unused	O
bit	O
;	O
and	O
the	O
C	B-Language
implementation	O
used	O
9-bit	O
bytes	B-Application
because	O
C	B-Language
requires	O
all	O
memory	O
to	O
be	O
byte-addressable	B-General_Concept
.	O
</s>
<s>
On	O
the	O
GE/Honeywell	O
machines	O
,	O
special	O
indirect	B-Language
addressing	I-Language
modes	I-Language
could	O
be	O
used	O
on	O
most	O
instruction	O
types	O
,	O
and	O
operated	O
on	O
a	O
byte	B-Application
pointer	O
which	O
could	O
operate	O
on	O
either	O
6-bit	O
or	O
9-bit	O
bytes	B-Application
.	O
</s>
<s>
Neither	O
of	O
these	O
machines	O
originally	O
had	O
direct	O
machine	O
support	O
for	O
random	O
access	O
to	O
bytes	B-Application
;	O
adjusting	O
a	O
byte	B-Application
pointer	O
to	O
point	O
N	O
bytes	B-Application
before	O
or	O
after	O
the	O
byte	B-Application
to	O
which	O
it	O
currently	O
pointed	O
required	O
a	O
sequence	O
of	O
multiple	O
instructions	O
.	O
</s>
<s>
The	O
KL10	B-Device
PDP-10	B-Device
model	O
extended	O
the	O
instruction	O
to	O
become	O
the	O
"	O
adjust	O
byte	B-Application
pointer	O
"	O
instruction	O
,	O
,	O
that	O
could	O
adjust	O
a	O
byte	B-Application
pointer	O
by	O
an	O
arbitrary	O
number	O
of	O
bytes	B-Application
.	O
</s>
