<s>
In	O
computing	O
,	O
the	O
term	O
text	B-Device
processing	I-Device
refers	O
to	O
the	O
theory	O
and	O
practice	O
of	O
automating	O
the	O
creation	O
or	O
manipulation	O
of	O
electronic	O
text	O
.	O
</s>
<s>
Text	O
usually	O
refers	O
to	O
all	O
the	O
alphanumeric	O
characters	O
specified	O
on	O
the	O
keyboard	O
of	O
the	O
person	O
engaging	O
the	O
practice	O
,	O
but	O
in	O
general	O
text	O
means	O
the	O
abstraction	B-Architecture
layer	I-Architecture
immediately	O
above	O
the	O
standard	O
character	B-General_Concept
encoding	I-General_Concept
of	O
the	O
target	O
text	O
.	O
</s>
<s>
The	O
text	B-Device
processing	I-Device
of	O
a	O
regular	B-Language
expression	I-Language
is	O
a	O
virtual	O
editing	O
machine	O
,	O
having	O
a	O
primitive	O
programming	O
language	O
that	O
has	O
named	O
registers	O
(	O
identifiers	O
)	O
,	O
and	O
named	O
positions	O
in	O
the	O
sequence	O
of	O
characters	O
comprising	O
the	O
text	O
.	O
</s>
<s>
The	O
text	B-Device
processing	I-Device
of	O
a	O
utility	B-Application
is	O
a	O
filter	O
program	O
,	O
or	O
filter	O
.	O
</s>
<s>
These	O
two	O
mechanisms	O
comprise	O
text	B-Device
processing	I-Device
.	O
</s>
<s>
Since	O
the	O
standardized	O
markup	O
such	O
as	O
ANSI	O
escape	O
codes	O
are	O
generally	O
invisible	O
to	O
the	O
editor	O
,	O
they	O
comprise	O
a	O
set	O
of	O
transitory	O
properties	O
that	O
become	O
at	O
times	O
indistinguishable	O
from	O
word	B-General_Concept
processing	I-General_Concept
.	O
</s>
<s>
But	O
the	O
definite	O
distinctions	O
from	O
word	B-General_Concept
processing	I-General_Concept
are	O
that	O
text	B-Device
processing	I-Device
proper	O
:	O
</s>
<s>
represents	O
"	O
text	B-Device
processing	I-Device
utilities	O
"	O
,	O
not	O
just	O
"	O
text	B-Application
editing	I-Application
"	O
applications	O
.	O
</s>
<s>
operates	O
directly	O
at	O
the	O
presentation	B-Application
layer	I-Application
rather	O
than	O
indirectly	O
at	O
the	O
application	B-Application
layer	I-Application
.	O
</s>
<s>
In	O
this	O
way	O
markup	O
such	O
as	O
font	O
and	O
color	O
are	O
not	O
really	O
a	O
distinguishing	O
factor	O
,	O
because	O
the	O
character	O
sequences	O
that	O
affect	O
font	O
and	O
color	O
are	O
simply	O
standard	O
characters	O
inserted	O
automatically	O
by	O
a	O
background	O
text	B-Device
processing	I-Device
mode	O
,	O
made	O
to	O
work	O
transparently	O
by	O
compliant	O
text	B-Application
editors	I-Application
,	O
yet	O
becoming	O
otherwise	O
visible	O
as	O
text	B-Device
processing	I-Device
commands	O
when	O
that	O
mode	O
is	O
not	O
in	O
effect	O
.	O
</s>
<s>
So	O
text	B-Device
processing	I-Device
is	O
defined	O
most	O
basically	O
(	O
but	O
not	O
entirely	O
)	O
around	O
the	O
visual	O
characters	O
(	O
or	O
graphemes	O
)	O
rather	O
than	O
the	O
standard	O
,	O
yet	O
invisible	O
characters	O
.	O
</s>
<s>
The	O
development	O
of	O
computer	O
text	B-Device
processing	I-Device
started	O
in	O
earnest	O
with	O
Kleene	O
's	O
formalizing	O
what	O
is	O
a	O
regular	O
language	O
.	O
</s>
<s>
Such	O
regular	B-Language
expressions	I-Language
could	O
then	O
become	O
a	O
mini-program	O
,	O
complete	O
with	O
a	O
compilation	O
process	O
,	O
available	O
to	O
perform	O
any	O
edit	O
,	O
once	O
that	O
language	O
was	O
extended	O
.	O
</s>
<s>
Similarly	O
,	O
filters	O
are	O
extended	O
by	O
evolving	O
particular	O
options	B-Application
.	O
</s>
<s>
An	O
editor	O
essentially	O
invokes	O
an	O
input	O
stream	O
and	O
directs	O
it	O
to	O
the	O
text	B-Device
processing	I-Device
environment	O
,	O
which	O
is	O
either	O
a	O
command	O
shell	O
or	O
a	O
text	B-Application
editor	I-Application
.	O
</s>
<s>
The	O
resulting	O
output	O
is	O
applicable	O
to	O
further	O
text	B-Device
processing	I-Device
,	O
the	O
final	O
result	O
of	O
which	O
is	O
comparable	O
to	O
a	O
single	O
application	O
of	O
an	O
algorithm	O
applied	O
once	O
by	O
a	O
more	O
sophisticated	O
and	O
structured	O
computer	O
program	O
.	O
</s>
<s>
Text	B-Device
processing	I-Device
is	O
,	O
unlike	O
an	O
algorithm	O
,	O
a	O
manually	O
administered	O
sequence	O
of	O
simpler	O
macros	O
that	O
are	O
the	O
pattern-action	O
expressions	O
and	O
filtering	O
mechanisms	O
.	O
</s>
<s>
In	O
either	O
case	O
the	O
programmer	O
's	O
intention	O
is	O
impressed	O
indirectly	O
upon	O
a	O
given	O
set	O
of	O
textual	O
characters	O
in	O
the	O
act	O
of	O
text	B-Device
processing	I-Device
.	O
</s>
<s>
The	O
results	O
of	O
a	O
text	B-Device
processing	I-Device
step	O
are	O
sometimes	O
only	O
hopeful	O
,	O
and	O
the	O
attempted	O
mechanism	O
is	O
often	O
subject	O
to	O
multiple	O
drafts	O
through	O
visual	O
feedback	O
,	O
until	O
the	O
regular	B-Language
expression	I-Language
or	O
markup	O
language	O
details	O
,	O
or	O
until	O
the	O
utility	B-Application
options	B-Application
,	O
are	O
fully	O
mastered	O
.	O
</s>
<s>
Text	B-Device
processing	I-Device
is	O
concerned	O
mostly	O
with	O
producing	O
textual	O
characters	O
at	O
the	O
highest	O
level	O
of	O
computing	O
,	O
where	O
its	O
activities	O
are	O
just	O
below	O
the	O
practical	O
uses	O
of	O
computingthe	O
manual	O
transmission	O
of	O
information	O
.	O
</s>
<s>
Ultimately	O
all	O
computing	O
is	O
text	B-Device
processing	I-Device
,	O
from	O
the	O
self-compiling	O
textual	O
characters	O
of	O
an	O
assembler	O
,	O
through	O
the	O
automated	O
programming	O
language	O
generated	O
to	O
handle	O
a	O
blob	O
of	O
graphical	O
data	O
,	O
and	O
finally	O
to	O
the	O
metacharacters	O
of	O
regular	B-Language
expressions	I-Language
which	O
groom	O
existing	O
text	O
documents	O
.	O
</s>
<s>
Text	B-Device
processing	I-Device
is	O
its	O
own	O
automation	O
.	O
</s>
<s>
Textual	O
characters	O
come	O
in	O
standardized	O
character	B-General_Concept
sets	I-General_Concept
containing	O
also	O
control	O
characters	O
such	O
as	O
newline	O
characters	O
,	O
which	O
arrange	O
text	O
.	O
</s>
<s>
Other	O
types	O
of	O
control	O
characters	O
arrange	O
the	O
transmission	O
,	O
define	O
the	O
character	B-General_Concept
sets	I-General_Concept
,	O
and	O
perform	O
other	O
housekeeping	O
tasks	O
.	O
</s>
