<s>
ASCII	O
(	O
)	O
,	O
abbreviated	O
from	O
American	O
Standard	O
Code	O
for	O
Information	O
Interchange	O
,	O
is	O
a	O
character	B-General_Concept
encoding	I-General_Concept
standard	O
for	O
electronic	O
communication	O
.	O
</s>
<s>
The	O
Internet	O
Assigned	O
Numbers	O
Authority	O
(	O
IANA	O
)	O
prefers	O
the	O
name	O
US-ASCII	O
for	O
this	O
character	B-General_Concept
encoding	I-General_Concept
.	O
</s>
<s>
Work	O
on	O
the	O
ASCII	O
standard	O
began	O
in	O
May	O
1961	O
,	O
with	O
the	O
first	O
meeting	O
of	O
the	O
American	O
Standards	O
Association	O
's	O
(	O
ASA	O
)	O
(	O
now	O
the	O
American	O
National	O
Standards	O
Institute	O
or	O
ANSI	O
)	O
X3.2	O
subcommittee	O
.	O
</s>
<s>
Compared	O
to	O
earlier	O
telegraph	O
codes	O
,	O
the	O
proposed	O
Bell	O
code	O
and	O
ASCII	O
were	O
both	O
ordered	O
for	O
more	O
convenient	O
sorting	B-Algorithm
(	O
i.e.	O
,	O
alphabetization	O
)	O
of	O
lists	O
and	O
added	O
features	O
for	O
devices	O
other	O
than	O
teleprinters	O
.	O
</s>
<s>
Originally	O
based	O
on	O
the	O
(	O
modern	O
)	O
English	O
alphabet	B-Application
,	O
ASCII	O
encodes	O
128	O
specified	O
characters	O
into	O
seven-bit	O
integers	O
as	O
shown	O
by	O
the	O
ASCII	O
chart	O
above	O
.	O
</s>
<s>
Ninety-five	O
of	O
the	O
encoded	O
characters	O
are	O
printable	O
:	O
these	O
include	O
the	O
digits	O
0	O
to	O
9	B-Application
,	O
lowercase	O
letters	O
a	O
to	O
z	B-Language
,	O
uppercase	O
letters	O
A	O
to	O
Z	B-Language
,	O
and	O
punctuation	O
symbols	O
.	O
</s>
<s>
For	O
example	O
,	O
lowercase	O
i	O
would	O
be	O
represented	O
in	O
the	O
ASCII	O
encoding	O
by	O
binary	O
1101001	O
=	O
hexadecimal	O
69	O
(	O
i	O
is	O
the	O
ninth	O
letter	O
)	O
=	O
decimal	B-Application
105	O
.	O
</s>
<s>
It	O
also	O
does	O
not	O
support	O
English	O
terms	O
with	O
diacritical	O
marks	O
such	O
as	O
résumé	O
and	O
jalapeño	O
,	O
or	O
proper	O
nouns	O
with	O
diacritical	O
marks	O
such	O
as	O
Beyoncé	O
.	O
</s>
<s>
The	O
American	O
Standard	O
Code	O
for	O
Information	O
Interchange	O
(	O
ASCII	O
)	O
was	O
developed	O
under	O
the	O
auspices	O
of	O
a	O
committee	O
of	O
the	O
American	O
Standards	O
Association	O
(	O
ASA	O
)	O
,	O
called	O
the	O
X3	O
committee	O
,	O
by	O
its	O
X3.2	O
(	O
later	O
X3L2	O
)	O
subcommittee	O
,	O
and	O
later	O
by	O
that	O
subcommittee	O
's	O
X3.2.4	O
working	O
group	O
(	O
now	O
INCITS	O
)	O
.	O
</s>
<s>
There	O
was	O
some	O
debate	O
at	O
the	O
time	O
whether	O
there	O
should	O
be	O
more	O
control	O
characters	O
rather	O
than	O
the	O
lowercase	O
alphabet	B-Application
.	O
</s>
<s>
The	O
indecision	O
did	O
not	O
last	O
long	O
:	O
during	O
May	O
1963	O
the	O
CCITT	O
Working	O
Party	O
on	O
the	O
New	O
Telegraph	O
Alphabet	B-Application
proposed	O
to	O
assign	O
lowercase	O
characters	O
to	O
sticks	O
6	O
and	O
7	O
,	O
and	O
International	O
Organization	O
for	O
Standardization	O
TC	O
97	O
SC	O
2	O
voted	O
during	O
October	O
to	O
incorporate	O
the	O
change	O
into	O
its	O
draft	O
standard	O
.	O
</s>
<s>
The	O
X3	O
committee	O
made	O
other	O
changes	O
,	O
including	O
other	O
new	O
characters	O
(	O
the	O
brace	O
and	O
vertical	O
bar	O
characters	O
)	O
,	O
renaming	O
some	O
control	O
characters	O
(	O
SOM	O
became	O
start	O
of	O
header	O
(	O
SOH	O
)	O
)	O
and	O
moving	O
or	O
removing	O
others	B-Protocol
(	O
RU	O
was	O
removed	O
)	O
.	O
</s>
<s>
They	O
proposed	O
a	O
9-track	B-Device
standard	O
for	O
magnetic	O
tape	O
,	O
and	O
attempted	O
to	O
deal	O
with	O
some	O
punched	B-Architecture
card	I-Architecture
formats	O
.	O
</s>
<s>
Like	O
other	O
character	B-General_Concept
encodings	I-General_Concept
,	O
ASCII	O
specifies	O
a	O
correspondence	O
between	O
digital	B-General_Concept
bit	O
patterns	O
and	O
character	O
symbols	O
(	O
i.e.	O
</s>
<s>
This	O
allows	O
digital	B-General_Concept
devices	O
to	O
communicate	O
with	O
each	O
other	O
and	O
to	O
process	O
,	O
store	O
,	O
and	O
communicate	O
character-oriented	O
information	O
such	O
as	O
written	O
language	O
.	O
</s>
<s>
To	O
include	O
all	O
these	O
,	O
and	O
control	O
characters	O
compatible	O
with	O
the	O
Comité	O
Consultatif	O
International	O
Téléphonique	O
et	O
Télégraphique	O
(	O
CCITT	O
)	O
International	O
Telegraph	O
Alphabet	B-Application
No	O
.	O
</s>
<s>
2	O
(	O
ITA2	O
)	O
standard	O
of	O
1924	O
,	O
FIELDATA	B-Device
(	O
1956	O
)	O
,	O
and	O
early	O
EBCDIC	B-Language
(	O
1963	O
)	O
,	O
more	O
than	O
64	O
codes	O
were	O
required	O
for	O
ASCII	O
.	O
</s>
<s>
ITA2	O
was	O
in	O
turn	O
based	O
on	O
the	O
5-bit	O
telegraph	O
code	O
that	O
Émile	O
Baudot	O
invented	O
in	O
1870	O
and	O
patented	O
in	O
1874	O
.	O
</s>
<s>
The	O
committee	O
debated	O
the	O
possibility	O
of	O
a	O
shift	B-Device
function	O
(	O
like	O
in	O
ITA2	O
)	O
,	O
which	O
would	O
allow	O
more	O
than	O
64	O
codes	O
to	O
be	O
represented	O
by	O
a	O
six-bit	O
code	O
.	O
</s>
<s>
In	O
a	O
shifted	O
code	O
,	O
some	O
character	B-General_Concept
codes	I-General_Concept
determine	O
choices	O
between	O
options	O
for	O
the	O
following	O
character	B-General_Concept
codes	I-General_Concept
.	O
</s>
<s>
It	O
allows	O
compact	O
encoding	O
,	O
but	O
is	O
less	O
reliable	O
for	O
data	O
transmission	O
,	O
as	O
an	O
error	O
in	O
transmitting	O
the	O
shift	B-Device
code	I-Device
typically	O
makes	O
a	O
long	O
part	O
of	O
the	O
transmission	O
unreadable	O
.	O
</s>
<s>
The	O
committee	O
considered	O
an	O
eight-bit	O
code	O
,	O
since	O
eight	O
bits	O
(	O
octets	O
)	O
would	O
allow	O
two	O
four-bit	O
patterns	O
to	O
efficiently	O
encode	O
two	O
digits	O
with	O
binary-coded	O
decimal	B-Application
.	O
</s>
<s>
Since	O
perforated	O
tape	O
at	O
the	O
time	O
could	O
record	O
eight	O
bits	O
in	O
one	O
position	O
,	O
it	O
also	O
allowed	O
for	O
a	O
parity	B-Error_Name
bit	I-Error_Name
for	O
error	B-Error_Name
checking	I-Error_Name
if	O
desired	O
.	O
</s>
<s>
Eight-bit	O
machines	O
(	O
with	O
octets	O
as	O
the	O
native	O
data	O
type	O
)	O
that	O
did	O
not	O
use	O
parity	B-Error_Name
checking	I-Error_Name
typically	O
set	O
the	O
eighth	O
bit	O
to	O
0	O
.	O
</s>
<s>
The	O
"	O
space	O
"	O
character	O
had	O
to	O
come	O
before	O
graphics	O
to	O
make	O
sorting	B-Algorithm
easier	O
,	O
so	O
it	O
became	O
position	O
20hex	O
;	O
for	O
the	O
same	O
reason	O
,	O
many	O
special	O
signs	O
commonly	O
used	O
as	O
separators	O
were	O
placed	O
before	O
digits	O
.	O
</s>
<s>
The	O
committee	O
decided	O
it	O
was	O
important	O
to	O
support	O
uppercase	O
64-character	O
alphabets	B-Application
,	O
and	O
chose	O
to	O
pattern	O
ASCII	O
so	O
it	O
could	O
be	O
reduced	O
easily	O
to	O
a	O
usable	O
64-character	O
set	O
of	O
graphic	O
codes	O
,	O
as	O
was	O
done	O
in	O
the	O
DEC	B-Application
SIXBIT	O
code	O
(	O
1963	O
)	O
.	O
</s>
<s>
The	O
digits	O
0	O
–	O
9	B-Application
are	O
prefixed	O
with	O
011	O
,	O
but	O
the	O
remaining	O
4	O
bits	O
correspond	O
to	O
their	O
respective	O
values	O
in	O
binary	O
,	O
making	O
conversion	O
with	O
binary-coded	O
decimal	B-Application
straightforward	O
(	O
for	O
example	O
,	O
5	B-Application
in	O
encoded	O
to	O
0110101	O
,	O
where	O
5	B-Application
is	O
0101	O
in	O
binary	O
)	O
.	O
</s>
<s>
2	O
(	O
1878	O
)	O
,	O
the	O
first	O
typewriter	O
with	O
a	O
shift	B-Device
key	I-Device
,	O
and	O
the	O
shifted	O
values	O
of	O
23456789	O
-	O
were	O
"	O
#$%_&'( 	O
)	O
early	O
typewriters	O
omitted	O
0	O
and	O
1	O
,	O
using	O
O	B-Language
(	O
capital	O
letter	O
o	B-Language
)	O
and	O
l	O
(	O
lowercase	O
letter	O
L	O
)	O
instead	O
,	O
but	O
1	O
!	O
</s>
<s>
Thus	O
,	O
in	O
ASCII	O
!	B-Device
</s>
<s>
"	O
#$%	O
were	O
placed	O
in	O
the	O
second	O
stick	O
,	O
positions	O
1	O
–	O
5	B-Application
,	O
corresponding	O
to	O
the	O
digits	O
1	O
–	O
5	B-Application
in	O
the	O
adjacent	O
stick	O
.	O
</s>
<s>
The	O
parentheses	O
could	O
not	O
correspond	O
to	O
9	B-Application
and	O
0	O
,	O
however	O
,	O
because	O
the	O
place	O
corresponding	O
to	O
0	O
was	O
taken	O
by	O
the	O
space	O
character	O
.	O
</s>
<s>
This	O
was	O
accommodated	O
by	O
removing	O
_	O
(	O
underscore	O
)	O
from	O
6	O
and	O
shifting	O
the	O
remaining	O
characters	O
,	O
which	O
corresponded	O
to	O
many	O
European	O
typewriters	O
that	O
placed	O
the	O
parentheses	O
with	O
8	O
and	O
9	B-Application
.	O
</s>
<s>
This	O
discrepancy	O
from	O
typewriters	O
led	O
to	O
bit-paired	B-Protocol
keyboards	I-Protocol
,	O
notably	O
the	O
Teletype	B-Application
Model	I-Application
33	I-Application
,	O
which	O
used	O
the	O
left-shifted	O
layout	O
corresponding	O
to	O
ASCII	O
,	O
differently	O
from	O
traditional	O
mechanical	O
typewriters	O
.	O
</s>
<s>
Electric	O
typewriters	O
,	O
notably	O
the	O
IBM	O
Selectric	O
(	O
1961	O
)	O
,	O
used	O
a	O
somewhat	O
different	O
layout	O
that	O
has	O
become	O
de	O
facto	O
standard	O
on	O
computers	O
following	O
the	O
IBM	B-Device
PC	I-Device
(	O
1981	O
)	O
,	O
especially	O
Model	B-Device
M	I-Device
(	O
1984	O
)	O
and	O
thus	O
shift	B-Device
values	O
for	O
symbols	O
on	O
modern	O
keyboards	O
do	O
not	O
correspond	O
as	O
closely	O
to	O
the	O
ASCII	O
table	O
as	O
earlier	O
keyboards	O
did	O
.	O
</s>
<s>
The	O
/	O
?	B-Device
</s>
<s>
2	O
,	O
and	O
the	O
,	O
< .>	O
pairs	O
were	O
used	O
on	O
some	O
keyboards	O
(	O
others	B-Protocol
,	O
including	O
the	O
No	O
.	O
</s>
<s>
2	O
,	O
did	O
not	O
shift	B-Device
,	O
(	O
comma	O
)	O
or	O
.	O
</s>
<s>
2	O
)	O
,	O
and	O
rearranged	O
mathematical	O
symbols	O
(	O
varied	O
conventions	O
,	O
commonly	O
-*	B-Protocol
=	O
+	O
)	O
to	O
:*	O
;	O
+	O
-	O
=	O
.	O
</s>
<s>
(	O
RU	O
)	O
,	O
a	O
reserved	O
device	O
control	O
(	O
DC0	O
)	O
,	O
synchronous	O
idle	O
(	O
SYNC	O
)	O
,	O
and	O
acknowledge	O
(	O
ACK	B-Protocol
)	O
.	O
</s>
<s>
ASCII	O
reserves	O
the	O
first	O
32	O
codes	O
(	O
numbers	O
0	O
–	O
31	O
decimal	B-Application
)	O
for	O
control	O
characters	O
,	O
which	O
are	O
characters	O
originally	O
intended	O
not	O
to	O
represent	O
printable	O
information	O
,	O
but	O
rather	O
to	O
control	O
devices	O
(	O
such	O
as	O
printers	O
)	O
that	O
make	O
use	O
of	O
ASCII	O
,	O
or	O
to	O
provide	O
meta-information	O
about	O
data	B-General_Concept
streams	I-General_Concept
such	O
as	O
those	O
stored	O
on	O
magnetic	O
tape	O
.	O
</s>
<s>
For	O
example	O
,	O
character	O
0x0A	O
represents	O
the	O
"	O
line	O
feed	O
"	O
function	O
(	O
which	O
causes	O
a	O
printer	O
to	O
advance	O
its	O
paper	O
)	O
,	O
and	O
character	O
8	O
represents	O
"	O
backspace	B-Device
"	O
.	O
</s>
<s>
The	O
ambiguity	O
this	O
caused	O
was	O
sometimes	O
intentional	O
,	O
for	O
example	O
where	O
a	O
character	O
would	O
be	O
used	O
slightly	O
differently	O
on	O
a	O
terminal	B-General_Concept
link	O
than	O
on	O
a	O
data	B-General_Concept
stream	I-General_Concept
,	O
and	O
sometimes	O
accidental	O
,	O
for	O
example	O
with	O
the	O
meaning	O
of	O
"	O
delete	B-Device
"	O
.	O
</s>
<s>
Probably	O
the	O
most	O
influential	O
single	O
device	O
affecting	O
the	O
interpretation	O
of	O
these	O
characters	O
was	O
the	O
Teletype	B-Application
Model	I-Application
33	I-Application
ASR	O
,	O
which	O
was	O
a	O
printing	O
terminal	B-General_Concept
with	O
an	O
available	O
paper	O
tape	O
reader/punch	O
option	O
.	O
</s>
<s>
In	O
particular	O
,	O
the	O
Teletype	B-Application
Model	I-Application
33	I-Application
machine	O
assignments	O
for	O
codes	O
17	O
(	O
control-Q	O
,	O
DC1	O
,	O
also	O
known	O
as	O
XON	O
)	O
,	O
19	O
(	O
control-S	O
,	O
DC3	O
,	O
also	O
known	O
as	O
XOFF	O
)	O
,	O
and	O
127	O
(	O
delete	B-Device
)	O
became	O
de	O
facto	O
standards	O
.	O
</s>
<s>
The	O
Model	O
33	O
was	O
also	O
notable	O
for	O
taking	O
the	O
description	O
of	O
control-G	O
(	O
code	O
7	O
,	O
BEL	O
,	O
meaning	O
audibly	O
alert	O
the	O
operator	O
)	O
literally	O
,	O
as	O
the	O
unit	O
contained	O
an	O
actual	O
bell	O
which	O
it	O
rang	O
when	O
it	O
received	O
a	O
BEL	O
character	O
.	O
</s>
<s>
Because	O
the	O
keytop	O
for	O
the	O
O	B-Language
key	O
also	O
showed	O
a	O
left-arrow	O
symbol	O
(	O
from	O
ASCII-1963	O
,	O
which	O
had	O
this	O
character	O
instead	O
of	O
underscore	O
)	O
,	O
a	O
noncompliant	O
use	O
of	O
code	O
15	O
(	O
control-O	O
,	O
shift	B-Device
in	O
)	O
interpreted	O
as	O
"	O
delete	B-Device
previous	O
character	O
"	O
was	O
also	O
adopted	O
by	O
many	O
early	O
timesharing	O
systems	O
but	O
eventually	O
became	O
neglected	O
.	O
</s>
<s>
When	O
a	O
Teletype	O
33	O
ASR	O
equipped	O
with	O
the	O
automatic	O
paper	O
tape	O
reader	O
received	O
a	O
control-S	O
(	O
XOFF	O
,	O
an	O
abbreviation	O
for	O
transmit	O
off	O
)	O
,	O
it	O
caused	O
the	O
tape	O
reader	O
to	O
stop	O
;	O
receiving	O
control-Q	O
(	O
XON	O
,	O
transmit	O
on	O
)	O
caused	O
the	O
tape	O
reader	O
to	O
resume	O
.	O
</s>
<s>
This	O
so-called	O
flow	O
control	O
technique	O
became	O
adopted	O
by	O
several	O
early	O
computer	B-General_Concept
operating	I-General_Concept
systems	I-General_Concept
as	O
a	O
"	O
handshaking	O
"	O
signal	O
warning	O
a	O
sender	O
to	O
stop	O
transmission	O
because	O
of	O
impending	O
buffer	B-General_Concept
overflow	I-General_Concept
;	O
it	O
persists	O
to	O
this	O
day	O
in	O
many	O
systems	O
as	O
a	O
manual	O
output	O
control	O
technique	O
.	O
</s>
<s>
On	O
some	O
systems	O
,	O
control-S	O
retains	O
its	O
meaning	O
but	O
control-Q	O
is	O
replaced	O
by	O
a	O
second	O
control-S	O
to	O
resume	O
output	O
.	O
</s>
<s>
The	O
33	O
ASR	O
also	O
could	O
be	O
configured	O
to	O
employ	O
control-R	O
(	O
DC2	O
)	O
and	O
control-T	O
(	O
DC4	O
)	O
to	O
start	O
and	O
stop	O
the	O
tape	O
punch	O
;	O
on	O
some	O
units	O
equipped	O
with	O
this	O
function	O
,	O
the	O
corresponding	O
control	O
character	O
lettering	O
on	O
the	O
keycap	O
above	O
the	O
letter	O
was	O
TAPE	O
and	O
TAPE	O
respectively	O
.	O
</s>
<s>
The	O
Teletype	O
could	O
not	O
move	O
its	O
typehead	O
backwards	O
,	O
so	O
it	O
did	O
not	O
have	O
a	O
key	O
on	O
its	O
keyboard	O
to	O
send	O
a	O
BS	B-Language
(	O
backspace	B-Device
)	O
.	O
</s>
<s>
Teletypes	O
were	O
commonly	O
used	O
with	O
the	O
less-expensive	O
computers	O
from	O
Digital	B-General_Concept
Equipment	O
Corporation	O
(	O
DEC	B-Application
)	O
;	O
these	O
systems	O
had	O
to	O
use	O
what	O
keys	O
were	O
available	O
,	O
and	O
thus	O
the	O
DEL	O
character	O
was	O
assigned	O
to	O
erase	O
the	O
previous	O
character	O
.	O
</s>
<s>
Because	O
of	O
this	O
,	O
DEC	B-Application
video	B-General_Concept
terminals	I-General_Concept
(	O
by	O
default	O
)	O
sent	O
the	O
DEL	O
character	O
for	O
the	O
key	O
marked	O
"	O
Backspace	B-Device
"	O
while	O
the	O
separate	O
key	O
marked	O
"	O
Delete	B-Device
"	O
sent	O
an	O
escape	B-Algorithm
sequence	I-Algorithm
;	O
many	O
other	O
competing	O
terminals	O
sent	O
a	O
BS	B-Language
character	O
for	O
the	O
backspace	B-Device
key	I-Device
.	O
</s>
<s>
The	O
Unix	B-Application
terminal	B-General_Concept
driver	O
could	O
only	O
use	O
one	O
character	O
to	O
erase	O
the	O
previous	O
character	O
,	O
this	O
could	O
be	O
set	O
to	O
BS	B-Language
or	O
DEL	O
,	O
but	O
not	O
both	O
,	O
resulting	O
in	O
recurring	O
situations	O
of	O
ambiguity	O
where	O
users	O
had	O
to	O
decide	O
depending	O
on	O
what	O
terminal	B-General_Concept
they	O
were	O
using	O
(	O
shells	B-Operating_System
that	O
allow	O
line	O
editing	O
,	O
such	O
as	O
ksh	B-Language
,	O
bash	B-Operating_System
,	O
and	O
zsh	B-Application
,	O
understand	O
both	O
)	O
.	O
</s>
<s>
The	O
assumption	O
that	O
no	O
key	O
sent	O
a	O
BS	B-Language
character	O
allowed	O
control+H	O
to	O
be	O
used	O
for	O
other	O
purposes	O
,	O
such	O
as	O
the	O
"	O
help	O
"	O
prefix	O
command	O
in	O
GNU	B-Application
Emacs	I-Application
.	O
</s>
<s>
The	O
"	O
escape	B-Algorithm
"	O
character	O
(	O
ESC	B-Algorithm
,	O
code	O
27	O
)	O
,	O
for	O
example	O
,	O
was	O
intended	O
originally	O
to	O
allow	O
sending	O
of	O
other	O
control	O
characters	O
as	O
literals	O
instead	O
of	O
invoking	O
their	O
meaning	O
,	O
an	O
"	O
escape	B-Algorithm
sequence	I-Algorithm
"	O
.	O
</s>
<s>
This	O
is	O
the	O
same	O
meaning	O
of	O
"	O
escape	B-Algorithm
"	O
encountered	O
in	O
URL	O
encodings	O
,	O
C	B-Language
language	I-Language
strings	O
,	O
and	O
other	O
systems	O
where	O
certain	O
characters	O
have	O
a	O
reserved	O
meaning	O
.	O
</s>
<s>
In	O
modern	O
usage	O
,	O
an	O
ESC	B-Algorithm
sent	O
to	O
the	O
terminal	B-General_Concept
usually	O
indicates	O
the	O
start	O
of	O
a	O
command	O
sequence	O
usually	O
in	O
the	O
form	O
of	O
a	O
so-called	O
"	O
ANSI	O
escape	B-Algorithm
code	O
"	O
(	O
or	O
,	O
more	O
properly	O
,	O
a	O
"	O
Control	O
Sequence	O
Introducer	O
"	O
)	O
from	O
ECMA-48	O
(	O
1972	O
)	O
and	O
its	O
successors	O
,	O
beginning	O
with	O
ESC	B-Algorithm
followed	O
by	O
a	O
"	O
[	O
"	O
(	O
left-bracket	O
)	O
character	O
.	O
</s>
<s>
In	O
contrast	O
,	O
an	O
ESC	B-Algorithm
sent	O
from	O
the	O
terminal	B-General_Concept
is	O
most	O
often	O
used	O
as	O
an	O
out-of-band	B-Protocol
character	O
used	O
to	O
terminate	B-Operating_System
an	O
operation	O
or	O
special	O
mode	O
,	O
as	O
in	O
the	O
TECO	B-Application
and	O
vi	B-Application
text	B-Application
editors	I-Application
.	O
</s>
<s>
In	O
graphical	B-Application
user	I-Application
interface	I-Application
(	O
GUI	B-Application
)	O
and	O
windowing	O
systems	O
,	O
ESC	B-Algorithm
generally	O
causes	O
an	O
application	O
to	O
abort	O
its	O
current	O
operation	O
or	O
to	O
exit	B-Operating_System
(	O
terminate	B-Operating_System
)	O
altogether	O
.	O
</s>
<s>
The	O
best	O
example	O
of	O
this	O
is	O
the	O
newline	O
problem	O
on	O
various	O
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
DEC	B-Application
operating	B-General_Concept
systems	I-General_Concept
(	O
OS/8	B-Operating_System
,	O
RT-11	B-Operating_System
,	O
RSX-11	B-Application
,	O
RSTS	B-Operating_System
,	O
TOPS-10	B-Operating_System
,	O
etc	O
.	O
)	O
</s>
<s>
By	O
the	O
time	O
so-called	O
"	O
glass	O
TTYs	O
"	O
(	O
later	O
called	O
CRTs	O
or	O
"	O
dumb	O
terminals	O
"	O
)	O
came	O
along	O
,	O
the	O
convention	O
was	O
so	O
well	O
established	O
that	O
backward	B-General_Concept
compatibility	I-General_Concept
necessitated	O
continuing	O
to	O
follow	O
it	O
.	O
</s>
<s>
When	O
Gary	O
Kildall	O
created	O
CP/M	B-Application
,	O
he	O
was	O
inspired	O
by	O
some	O
of	O
the	O
command	O
line	O
interface	O
conventions	O
used	O
in	O
DEC	B-Application
's	O
RT-11	B-Operating_System
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
Until	O
the	O
introduction	O
of	O
PC	O
DOS	B-Device
in	O
1981	O
,	O
IBM	O
had	O
no	O
influence	O
in	O
this	O
because	O
their	O
1970s	O
operating	B-General_Concept
systems	I-General_Concept
used	O
EBCDIC	B-Language
encoding	O
instead	O
of	O
ASCII	O
,	O
and	O
they	O
were	O
oriented	O
toward	O
punch-card	B-Architecture
input	O
and	O
line	O
printer	O
output	O
on	O
which	O
the	O
concept	O
of	O
"	O
carriage	O
return	O
"	O
was	O
meaningless	O
.	O
</s>
<s>
IBM	O
's	O
PC	O
DOS	B-Device
(	O
also	O
marketed	O
as	O
MS-DOS	B-Application
by	O
Microsoft	O
)	O
inherited	O
the	O
convention	O
by	O
virtue	O
of	O
being	O
loosely	O
based	O
on	O
CP/M	B-Application
,	O
and	O
Windows	O
in	O
turn	O
inherited	O
it	O
from	O
MS-DOS	B-Application
.	O
</s>
<s>
To	O
simplify	O
matters	O
,	O
plain	O
text	O
data	B-General_Concept
streams	I-General_Concept
,	O
including	O
files	O
,	O
on	O
Multics	B-Application
used	O
line	O
feed	O
(	O
LF	O
)	O
alone	O
as	O
a	O
line	O
terminator	O
.	O
</s>
<s>
Unix	B-Application
and	O
Unix-like	B-Operating_System
systems	I-Operating_System
,	O
and	O
Amiga	B-Device
systems	O
,	O
adopted	O
this	O
convention	O
from	O
Multics	B-Application
.	O
</s>
<s>
On	O
the	O
other	O
hand	O
,	O
the	O
original	O
Macintosh	B-Operating_System
OS	I-Operating_System
,	O
Apple	B-Operating_System
DOS	I-Operating_System
,	O
and	O
ProDOS	B-Operating_System
used	O
carriage	O
return	O
(	O
CR	O
)	O
alone	O
as	O
a	O
line	O
terminator	O
;	O
however	O
,	O
since	O
Apple	O
has	O
now	O
replaced	O
these	O
obsolete	O
operating	B-General_Concept
systems	I-General_Concept
with	O
the	O
Unix-based	O
macOS	B-Application
operating	B-General_Concept
system	I-General_Concept
,	O
they	O
now	O
use	O
line	O
feed	O
(	O
LF	O
)	O
as	O
well	O
.	O
</s>
<s>
The	O
Radio	B-Device
Shack	I-Device
TRS-80	I-Device
also	O
used	O
a	O
lone	O
CR	O
to	O
terminate	B-Operating_System
lines	O
.	O
</s>
<s>
Computers	O
attached	O
to	O
the	O
ARPANET	O
included	O
machines	O
running	O
operating	B-General_Concept
systems	I-General_Concept
such	O
as	O
TOPS-10	B-Operating_System
and	O
TENEX	B-Operating_System
using	O
CR-LF	O
line	O
endings	O
;	O
machines	O
running	O
operating	B-General_Concept
systems	I-General_Concept
such	O
as	O
Multics	B-Application
using	O
LF	O
line	O
endings	O
;	O
and	O
machines	O
running	O
operating	B-General_Concept
systems	I-General_Concept
such	O
as	O
OS/360	B-Application
that	O
represented	O
lines	O
as	O
a	O
character	O
count	O
followed	O
by	O
the	O
characters	O
of	O
the	O
line	O
and	O
which	O
used	O
EBCDIC	B-Language
rather	O
than	O
ASCII	O
encoding	O
.	O
</s>
<s>
The	O
Telnet	B-Protocol
protocol	O
defined	O
an	O
ASCII	O
"	O
Network	O
Virtual	O
Terminal	B-General_Concept
"	O
(	O
NVT	O
)	O
,	O
so	O
that	O
connections	O
between	O
hosts	O
with	O
different	O
line-ending	O
conventions	O
and	O
character	B-General_Concept
sets	I-General_Concept
could	O
be	O
supported	O
by	O
transmitting	O
a	O
standard	O
text	O
format	O
over	O
the	O
network	O
.	O
</s>
<s>
Telnet	B-Protocol
used	O
ASCII	O
along	O
with	O
CR-LF	O
line	O
endings	O
,	O
and	O
software	O
using	O
other	O
conventions	O
would	O
translate	O
between	O
the	O
local	O
conventions	O
and	O
the	O
NVT	O
.	O
</s>
<s>
The	O
File	B-Protocol
Transfer	I-Protocol
Protocol	I-Protocol
adopted	O
the	O
Telnet	B-Protocol
protocol	O
,	O
including	O
use	O
of	O
the	O
Network	O
Virtual	O
Terminal	B-General_Concept
,	O
for	O
use	O
when	O
transmitting	O
commands	O
and	O
transferring	O
data	O
in	O
the	O
default	O
ASCII	O
mode	O
.	O
</s>
<s>
This	O
adds	O
complexity	O
to	O
implementations	O
of	O
those	O
protocols	O
,	O
and	O
to	O
other	O
network	O
protocols	O
,	O
such	O
as	O
those	O
used	O
for	O
E-mail	O
and	O
the	O
World	O
Wide	O
Web	O
,	O
on	O
systems	O
not	O
using	O
the	O
NVT	O
's	O
CR-LF	O
line-ending	O
convention	O
.	O
</s>
<s>
The	O
PDP-6	O
monitor	O
,	O
and	O
its	O
PDP-10	O
successor	O
TOPS-10	B-Operating_System
,	O
used	O
control-Z	O
(	O
SUB	O
)	O
as	O
an	O
end-of-file	B-Language
indication	O
for	O
input	O
from	O
a	O
terminal	B-General_Concept
.	O
</s>
<s>
Some	O
operating	B-General_Concept
systems	I-General_Concept
such	O
as	O
CP/M	B-Application
tracked	O
file	O
length	O
only	O
in	O
units	O
of	O
disk	O
blocks	O
,	O
and	O
used	O
control-Z	O
to	O
mark	O
the	O
end	O
of	O
the	O
actual	O
text	O
in	O
the	O
file	O
.	O
</s>
<s>
For	O
these	O
reasons	O
,	O
EOF	O
,	O
or	O
end-of-file	B-Language
,	O
was	O
used	O
colloquially	O
and	O
conventionally	O
as	O
a	O
three-letter	O
acronym	O
for	O
control-Z	O
instead	O
of	O
SUBstitute	O
.	O
</s>
<s>
The	O
end-of-text	O
character	O
(	O
ETX	O
)	O
,	O
also	O
known	O
as	O
control-C	B-Device
,	O
was	O
inappropriate	O
for	O
a	O
variety	O
of	O
reasons	O
,	O
while	O
using	O
control-Z	O
as	O
the	O
control	O
character	O
to	O
end	O
a	O
file	O
is	O
analogous	O
to	O
the	O
letter	O
Z	B-Language
's	O
position	O
at	O
the	O
end	O
of	O
the	O
alphabet	B-Application
,	O
and	O
serves	O
as	O
a	O
very	O
convenient	O
mnemonic	O
aid	O
.	O
</s>
<s>
A	O
historically	O
common	O
and	O
still	O
prevalent	O
convention	O
uses	O
the	O
ETX	O
character	O
convention	O
to	O
interrupt	O
and	O
halt	O
a	O
program	O
via	O
an	O
input	O
data	B-General_Concept
stream	I-General_Concept
,	O
usually	O
from	O
a	O
keyboard	O
.	O
</s>
<s>
The	O
Unix	B-Application
terminal	B-General_Concept
driver	O
uses	O
the	O
end-of-transmission	O
character	O
(	O
EOT	O
)	O
,	O
also	O
known	O
as	O
control-D	O
,	O
to	O
indicate	O
the	O
end	O
of	O
a	O
data	B-General_Concept
stream	I-General_Concept
.	O
</s>
<s>
In	O
the	O
C	B-Language
programming	I-Language
language	I-Language
,	O
and	O
in	O
Unix	B-Application
conventions	O
,	O
the	O
null	O
character	O
is	O
used	O
to	O
terminate	B-Operating_System
text	O
strings	O
;	O
such	O
null-terminated	B-Data_Structure
strings	I-Data_Structure
can	O
be	O
known	O
in	O
abbreviation	O
as	O
ASCIZ	B-Data_Structure
or	O
ASCIIZ	B-Data_Structure
,	O
where	O
here	O
Z	B-Language
stands	O
for	O
"	O
zero	O
"	O
.	O
</s>
<s>
Code	O
7Fhex	O
corresponds	O
to	O
the	O
non-printable	O
"	O
delete	B-Device
"	O
(	O
DEL	O
)	O
control	O
character	O
and	O
is	O
therefore	O
omitted	O
from	O
this	O
chart	O
;	O
it	O
is	O
covered	O
in	O
the	O
previous	O
section	O
's	O
chart	O
.	O
</s>
<s>
Binary	O
Oct	O
Dec	B-Application
Hex	O
Glyph	O
1963	O
1965	O
1967010	O
0000	O
040	O
32	O
20	O
space010	O
0001	O
041	O
33	O
21	O
!	O
010	O
0010	O
042	O
34	O
22	O
"	O
010	O
0011	O
043	O
35	O
23	O
#010	O
0100	O
044	O
36	O
24	O
$010	O
0101	O
045	O
37	O
25	O
%010	O
0110	O
046	O
38	O
26	O
&	O
010	O
0111	O
047	O
39	O
27	O
'	O
010	O
1000	O
050	O
40	O
28	O
(	O
010	O
1001	O
051	O
41	O
29	O
)	O
010	O
1010	O
052	O
42	O
2A	O
*	O
010	O
1011	O
053	O
43	O
2B	O
+010	O
1100	O
054	O
44	O
2C	O
,	O
010	O
1101	O
055	O
45	O
2D	O
-010	O
1110	O
056	O
46	O
2E	O
.010	O
1111	O
057	O
47	O
2F	O
/011	O
0000	O
060	O
48	O
30	O
0011	O
0001	O
061	O
49	O
31	O
1011	O
0010	O
062	O
50	O
32	O
2011	O
0011	O
063	O
51	O
33	O
3011	O
0100	O
064	O
52	O
34	O
4011	O
0101	O
065	O
53	O
35	O
5011	O
0110	O
066	O
54	O
36	O
6011	O
0111	O
067	O
55	O
37	O
7011	O
1000	O
070	O
56	O
38	O
8011	O
1001	O
071	O
57	O
39	O
9011	O
1010	O
072	O
58	O
3A	O
:011	O
1011	O
073	O
59	O
3B	O
;	O
011	O
1100	O
074	O
60	O
3C	O
<	O
011	O
1101	O
075	O
61	O
3D	O
=	O
011	O
1110	O
076	O
62	O
3E	O
>011	O
1111	O
077	O
63	O
3F	O
?	O
100	O
0000	O
100	O
64	O
40	O
@	O
`	O
@100	O
0001	O
101	O
65	O
41	O
A100	O
0010	O
102	O
66	O
42	O
B100	O
0011	O
103	O
67	O
43	O
C100	O
0100	O
104	O
68	O
44	O
D100	O
0101	O
105	O
69	O
45	O
E100	O
0110	O
106	O
70	O
46	O
F100	O
0111	O
107	O
71	O
47	O
G100	O
1000	O
110	O
72	O
48	O
H100	O
1001	O
111	O
73	O
49	O
I100	O
1010	O
112	O
74	O
4A	O
J100	O
1011	O
113	O
75	O
4B	O
K100	O
1100	O
114	O
76	O
4C	O
L100	O
1101	O
115	O
77	O
4D	O
M100	O
1110	O
116	O
78	O
4E	O
N100	O
1111	O
117	O
79	O
4F	O
O101	O
0000	O
120	O
80	O
50	O
P101	O
0001	O
121	O
81	O
51	O
Q101	O
0010	O
122	O
82	O
52	O
R101	O
0011	O
123	O
83	O
53	O
S101	O
0100	O
124	O
84	O
54	O
T101	O
0101	O
125	O
85	O
55	O
U101	O
0110	O
126	O
86	O
56	O
V101	O
0111	O
127	O
87	O
57	O
W101	O
1000	O
130	O
88	O
58	O
X101	O
1001	O
131	O
89	O
59	O
Y101	O
1010	O
132	O
90	O
5A	O
Z101	O
1011	O
133	O
91	O
5B	O
[	O
101	O
1100	O
134	O
92	O
5C	O
\	O
~	O
\101	O
1101	O
135	O
93	O
5D	O
]	O
101	O
1110	O
136	O
94	O
5E	O
↑	O
^101	O
1111	O
137	O
95	O
5F	O
←	O
_110	O
0000	O
140	O
96	O
60	O
@	O
`110	O
0001	O
141	O
97	O
61	O
a110	O
0010	O
142	O
98	O
62	O
b110	O
0011	O
143	O
99	O
63	O
c110	O
0100	O
144	O
100	O
64	O
d110	O
0101	O
145	O
101	O
65	O
e110	O
0110	O
146	O
102	O
66	O
f110	O
0111	O
147	O
103	O
67	O
g110	O
1000	O
150	O
104	O
68	O
h110	O
1001	O
151	O
105	O
69	O
i110	O
1010	O
152	O
106	O
6A	O
j110	O
1011	O
153	O
107	O
6B	O
k110	O
1100	O
154	O
108	O
6C	O
l110	O
1101	O
155	O
109	O
6D	O
m110	O
1110	O
156	O
110	O
6E	O
n110	O
1111	O
157	O
111	O
6F	O
o111	O
0000	O
160	O
112	O
70	O
p111	O
0001	O
161	O
113	O
71	O
q111	O
0010	O
162	O
114	O
72	O
r111	O
0011	O
163	O
115	O
73	O
s111	O
0100	O
164	O
116	O
74	O
t111	O
0101	O
165	O
117	O
75	O
u111	O
0110	O
166	O
118	O
76	O
v111	O
0111	O
167	O
119	O
77	O
w111	O
1000	O
170	O
120	O
78	O
x111	O
1001	O
171	O
121	O
79	O
y111	O
1010	O
172	O
122	O
7A	O
z111	O
1011	O
173	O
123	O
7B	O
{	O
111	O
1100	O
174	O
124	O
7C	O
ACK	B-Protocol
¬	O
|111	O
1101	O
175	O
125	O
7D	O
}	O
111	O
1110	O
176	O
126	O
7E	O
ESC	B-Algorithm
|	O
~	O
</s>
<s>
ASCII	O
was	O
first	O
used	O
commercially	O
during	O
1963	O
as	O
a	O
seven-bit	O
teleprinter	O
code	O
for	O
American	O
Telephone	O
&	O
Telegraph	O
's	O
TWX	O
(	O
TeletypeWriter	O
eXchange	O
)	O
network	O
.	O
</s>
<s>
TWX	O
originally	O
used	O
the	O
earlier	O
five-bit	O
ITA2	O
,	O
which	O
was	O
also	O
used	O
by	O
the	O
competing	O
Telex	B-Application
teleprinter	O
system	O
.	O
</s>
<s>
Bob	O
Bemer	O
introduced	O
features	O
such	O
as	O
the	O
escape	B-Algorithm
sequence	I-Algorithm
.	O
</s>
<s>
On	O
March	O
11	O
,	O
1968	O
,	O
US	O
President	O
Lyndon	O
B	B-Language
.	O
Johnson	O
mandated	O
that	O
all	O
computers	O
purchased	O
by	O
the	O
United	O
States	O
Federal	O
Government	O
support	O
ASCII	O
,	O
stating	O
:	O
</s>
<s>
ASCII	O
was	O
the	O
most	O
common	O
character	B-General_Concept
encoding	I-General_Concept
on	O
the	O
World	O
Wide	O
Web	O
until	O
December	O
2007	O
,	O
when	O
UTF-8	O
encoding	O
surpassed	O
it	O
;	O
UTF-8	O
is	O
backward	B-General_Concept
compatible	I-General_Concept
with	O
ASCII	O
.	O
</s>
<s>
As	O
computer	O
technology	O
spread	O
throughout	O
the	O
world	O
,	O
different	O
standards	O
bodies	O
and	O
corporations	O
developed	O
many	O
variations	O
of	O
ASCII	O
to	O
facilitate	O
the	O
expression	O
of	O
non-English	O
languages	O
that	O
used	O
Roman-based	O
alphabets	B-Application
.	O
</s>
<s>
One	O
could	O
class	O
some	O
of	O
these	O
variations	O
as	O
"	O
ASCII	B-Protocol
extensions	I-Protocol
"	O
,	O
although	O
some	O
misuse	O
that	O
term	O
to	O
represent	O
all	O
variants	O
,	O
including	O
those	O
that	O
do	O
not	O
preserve	O
ASCII	O
's	O
character-map	O
in	O
the	O
7-bit	O
range	O
.	O
</s>
<s>
Furthermore	O
,	O
the	O
ASCII	B-Protocol
extensions	I-Protocol
have	O
also	O
been	O
mislabelled	O
as	O
ASCII	O
.	O
</s>
<s>
From	O
early	O
in	O
its	O
development	O
,	O
ASCII	O
was	O
intended	O
to	O
be	O
just	O
one	O
of	O
several	O
national	O
variants	O
of	O
an	O
international	O
character	B-General_Concept
code	I-General_Concept
standard	O
.	O
</s>
<s>
Other	O
international	O
standards	O
bodies	O
have	O
ratified	O
character	B-General_Concept
encodings	I-General_Concept
such	O
as	O
ISO	O
646	O
(	O
1967	O
)	O
that	O
are	O
identical	O
or	O
nearly	O
identical	O
to	O
ASCII	O
,	O
with	O
extensions	O
for	O
characters	O
outside	O
the	O
English	O
alphabet	B-Application
and	O
symbols	O
used	O
outside	O
the	O
United	O
States	O
,	O
such	O
as	O
the	O
symbol	O
for	O
the	O
United	O
Kingdom	O
's	O
pound	O
sterling	O
( £	O
)	O
;	O
e.g.	O
</s>
<s>
Many	O
other	O
countries	O
developed	O
variants	O
of	O
ASCII	O
to	O
include	O
non-English	O
letters	O
(	O
e.g.	O
</s>
<s>
é	O
,	O
ñ	O
,	O
ß	O
,	O
Ł	O
)	O
,	O
currency	O
symbols	O
(	O
e.g.	O
</s>
<s>
However	O
,	O
the	O
four	O
years	O
that	O
elapsed	O
between	O
the	O
publication	O
of	O
ASCII-1963	O
and	O
ISO	O
's	O
first	O
acceptance	O
of	O
an	O
international	O
recommendation	O
during	O
1967	O
caused	O
ASCII	O
's	O
choices	O
for	O
the	O
national	O
use	O
characters	O
to	O
seem	O
to	O
be	O
de	O
facto	O
standards	O
for	O
the	O
world	O
,	O
causing	O
confusion	O
and	O
incompatibility	O
once	O
other	O
countries	O
did	O
begin	O
to	O
make	O
their	O
own	O
assignments	O
to	O
these	O
code	O
points	O
.	O
</s>
<s>
ISO/IEC	O
646	O
,	O
like	O
ASCII	O
,	O
is	O
a	O
7-bit	O
character	B-General_Concept
set	I-General_Concept
.	O
</s>
<s>
Escape	B-Algorithm
codes	O
were	O
defined	O
to	O
indicate	O
which	O
national	O
variant	O
applied	O
to	O
a	O
piece	O
of	O
text	O
,	O
but	O
they	O
were	O
rarely	O
used	O
,	O
so	O
it	O
was	O
often	O
impossible	O
to	O
know	O
what	O
variant	O
to	O
work	O
with	O
and	O
,	O
therefore	O
,	O
which	O
character	O
a	O
code	O
represented	O
,	O
and	O
in	O
general	O
,	O
text-processing	O
systems	O
could	O
cope	O
with	O
only	O
one	O
variant	O
anyway	O
.	O
</s>
<s>
C	B-Language
trigraphs	I-Language
were	O
created	O
to	O
solve	O
this	O
problem	O
for	O
ANSI	O
C	B-Language
,	O
although	O
their	O
late	O
introduction	O
and	O
inconsistent	O
implementation	O
in	O
compilers	O
limited	O
their	O
use	O
.	O
</s>
<s>
(	O
for	O
example	O
,	O
in	O
e-mail	O
or	O
Usenet	B-Application
)	O
contained	O
"	O
{	O
,	O
}	O
"	O
and	O
similar	O
variants	O
in	O
the	O
middle	O
of	O
words	O
,	O
something	O
those	O
programmers	O
got	O
used	O
to	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
Swedish	O
programmer	O
mailing	O
another	O
programmer	O
asking	O
if	O
they	O
should	O
go	O
for	O
lunch	O
,	O
could	O
get	O
"	O
N{	O
jag	O
har	O
sm|rg}sar	O
"	O
as	O
the	O
answer	O
,	O
which	O
should	O
be	O
"	O
Nä	O
jag	O
har	O
smörgåsar	O
"	O
meaning	O
"	O
No	O
I	O
've	O
got	O
sandwiches	O
"	O
.	O
</s>
<s>
This	O
means	O
that	O
,	O
for	O
example	O
,	O
the	O
file	O
path	O
C:\Users\Smith	O
is	O
shown	O
as	O
C	B-Language
:	O
¥Users¥Smith	O
(	O
in	O
Japan	O
)	O
or	O
C	B-Language
:	O
₩Users₩Smith	O
(	O
in	O
Korea	O
)	O
.	O
</s>
<s>
In	O
Europe	O
,	O
teletext	O
character	B-General_Concept
sets	I-General_Concept
,	O
which	O
are	O
variants	O
of	O
ASCII	O
,	O
are	O
used	O
for	O
broadcast	O
TV	O
subtitles	O
,	O
defined	O
by	O
World	O
System	O
Teletext	O
and	O
broadcast	O
using	O
the	O
DVB-TXT	O
standard	O
for	O
embedding	O
teletext	O
into	O
DVB	O
transmissions	O
.	O
</s>
<s>
In	O
the	O
case	O
that	O
the	O
subtitles	O
were	O
initially	O
authored	O
for	O
teletext	O
and	O
converted	O
,	O
the	O
derived	O
subtitle	O
formats	O
are	O
constrained	O
to	O
the	O
same	O
character	B-General_Concept
sets	I-General_Concept
.	O
</s>
<s>
Eventually	O
,	O
as	O
8-	O
,	O
16-	O
,	O
and	O
32-bit	O
(	O
and	O
later	O
64-bit	B-Device
)	O
computers	O
began	O
to	O
replace	O
12-	O
,	O
18-	O
,	O
and	O
36-bit	O
computers	O
as	O
the	O
norm	O
,	O
it	O
became	O
common	O
to	O
use	O
an	O
8-bit	O
byte	O
to	O
store	O
each	O
character	O
in	O
memory	O
,	O
providing	O
an	O
opportunity	O
for	O
extended	O
,	O
8-bit	O
relatives	O
of	O
ASCII	O
.	O
</s>
<s>
In	O
most	O
cases	O
these	O
developed	O
as	O
true	O
extensions	O
of	O
ASCII	O
,	O
leaving	O
the	O
original	O
character-mapping	O
intact	O
,	O
but	O
adding	O
additional	O
character	O
definitions	O
after	O
the	O
first	O
128	O
(	O
i.e.	O
,	O
7-bit	O
)	O
characters	O
.	O
</s>
<s>
Most	O
early	O
home	O
computer	O
systems	O
developed	O
their	O
own	O
8-bit	O
character	B-General_Concept
sets	I-General_Concept
containing	O
line-drawing	O
and	O
game	O
glyphs	O
,	O
and	O
often	O
filled	O
in	O
some	O
or	O
all	O
of	O
the	O
control	O
characters	O
from	O
0	O
to	O
31	O
with	O
more	O
graphics	O
.	O
</s>
<s>
Kaypro	O
CP/M	B-Application
computers	O
used	O
the	O
"	O
upper	O
"	O
128	O
characters	O
for	O
the	O
Greek	O
alphabet	B-Application
.	O
</s>
<s>
The	O
PETSCII	B-Protocol
code	O
Commodore	O
International	O
used	O
for	O
their	O
8-bit	O
systems	O
is	O
probably	O
unique	O
among	O
post-1970	O
codes	O
in	O
being	O
based	O
on	O
ASCII-1963	O
,	O
instead	O
of	O
the	O
more	O
common	O
ASCII-1967	O
,	O
such	O
as	O
found	O
on	O
the	O
ZX	O
Spectrum	O
computer	O
.	O
</s>
<s>
Atari	B-Protocol
8-bit	O
computers	O
and	O
Galaksija	O
computers	O
also	O
used	O
ASCII	O
variants	O
.	O
</s>
<s>
The	O
IBM	B-Device
PC	I-Device
defined	O
code	O
page	O
437	O
,	O
which	O
replaced	O
the	O
control	O
characters	O
with	O
graphic	O
symbols	O
such	O
as	O
smiley	B-Protocol
faces	I-Protocol
,	O
and	O
mapped	O
additional	O
graphic	O
characters	O
to	O
the	O
upper	O
128	O
positions	O
.	O
</s>
<s>
Operating	B-General_Concept
systems	I-General_Concept
such	O
as	O
DOS	B-Device
supported	O
these	O
code	O
pages	O
,	O
and	O
manufacturers	O
of	O
IBM	B-Device
PCs	I-Device
supported	O
them	O
in	O
hardware	O
.	O
</s>
<s>
Digital	B-General_Concept
Equipment	O
Corporation	O
developed	O
the	O
Multinational	O
Character	B-General_Concept
Set	I-General_Concept
(	O
DEC-MCS	O
)	O
for	O
use	O
in	O
the	O
popular	O
VT220	B-Device
terminal	B-General_Concept
as	O
one	O
of	O
the	O
first	O
extensions	O
designed	O
more	O
for	O
international	O
languages	O
than	O
for	O
block	O
graphics	O
.	O
</s>
<s>
The	O
Macintosh	O
defined	O
Mac	B-Application
OS	I-Application
Roman	O
and	O
Postscript	O
defined	O
another	O
character	B-General_Concept
set	I-General_Concept
:	O
both	O
sets	O
contained	O
"	O
international	O
"	O
letters	O
,	O
typographic	O
symbols	O
and	O
punctuation	O
marks	O
instead	O
of	O
graphics	O
,	O
more	O
like	O
modern	O
character	B-General_Concept
sets	I-General_Concept
.	O
</s>
<s>
The	O
ISO/IEC	O
8859	O
standard	O
(	O
derived	O
from	O
the	O
DEC-MCS	O
)	O
finally	O
provided	O
a	O
standard	O
that	O
most	O
systems	O
copied	O
(	O
at	O
least	O
as	O
accurately	O
as	O
they	O
copied	O
ASCII	O
,	O
but	O
with	O
many	O
substitutions	O
)	O
.	O
</s>
<s>
ISO-8859-1	O
,	O
Windows-1252	O
,	O
and	O
the	O
original	O
7-bit	O
ASCII	O
were	O
the	O
most	O
common	O
character	B-General_Concept
encodings	I-General_Concept
until	O
2008	O
when	O
UTF-8	O
became	O
more	O
common	O
.	O
</s>
<s>
Unicode	O
and	O
the	O
ISO/IEC	O
10646	O
Universal	O
Character	B-General_Concept
Set	I-General_Concept
(	O
UCS	O
)	O
have	O
a	O
much	O
wider	O
array	O
of	O
characters	O
and	O
their	O
various	O
encoding	O
forms	O
have	O
begun	O
to	O
supplant	O
ISO/IEC	O
8859	O
and	O
ASCII	O
rapidly	O
in	O
many	O
environments	O
.	O
</s>
<s>
ASCII	O
was	O
incorporated	O
into	O
the	O
Unicode	O
(	O
1991	O
)	O
character	B-General_Concept
set	I-General_Concept
as	O
the	O
first	O
128	O
symbols	O
,	O
so	O
the	O
7-bit	O
ASCII	O
characters	O
have	O
the	O
same	O
numeric	O
codes	O
in	O
both	O
sets	O
.	O
</s>
<s>
This	O
allows	O
UTF-8	O
to	O
be	O
backward	B-General_Concept
compatible	I-General_Concept
with	O
7-bit	O
ASCII	O
,	O
as	O
a	O
UTF-8	O
file	O
containing	O
only	O
ASCII	O
characters	O
is	O
identical	O
to	O
an	O
ASCII	O
file	O
containing	O
the	O
same	O
sequence	O
of	O
characters	O
.	O
</s>
<s>
Even	O
more	O
importantly	O
,	O
forward	B-General_Concept
compatibility	I-General_Concept
is	O
ensured	O
as	O
software	O
that	O
recognizes	O
only	O
7-bit	O
ASCII	O
characters	O
as	O
special	O
and	O
does	O
not	O
alter	O
bytes	O
with	O
the	O
highest	O
bit	O
set	O
(	O
as	O
is	O
often	O
done	O
to	O
support	O
8-bit	B-Protocol
ASCII	I-Protocol
extensions	O
such	O
as	O
ISO-8859-1	O
)	O
will	O
preserve	O
UTF-8	O
data	O
unchanged	O
.	O
</s>
