<s>
Text	B-Application
mode	I-Application
is	O
a	O
computer	B-Device
display	I-Device
mode	O
in	O
which	O
content	O
is	O
internally	O
represented	O
on	O
a	O
computer	B-Device
screen	I-Device
in	O
terms	O
of	O
characters	O
rather	O
than	O
individual	O
pixels	B-Algorithm
.	O
</s>
<s>
Typically	O
,	O
the	O
screen	O
consists	O
of	O
a	O
uniform	O
rectangular	O
grid	O
of	O
character	B-Application
cells	I-Application
,	O
each	O
of	O
which	O
contains	O
one	O
of	O
the	O
characters	O
of	O
a	O
character	B-General_Concept
set	I-General_Concept
;	O
at	O
the	O
same	O
time	O
,	O
contrasted	O
to	O
all	O
points	O
addressable	O
(	O
APA	O
)	O
mode	O
or	O
other	O
kinds	O
of	O
computer	O
graphics	O
modes	O
.	O
</s>
<s>
Text	B-Application
mode	I-Application
applications	O
communicate	O
with	O
the	O
user	O
by	O
using	O
command-line	B-Application
interfaces	I-Application
and	O
text	B-Application
user	I-Application
interfaces	I-Application
.	O
</s>
<s>
Many	O
character	B-General_Concept
sets	I-General_Concept
used	O
in	O
text	B-Application
mode	I-Application
applications	O
also	O
contain	O
a	O
limited	O
set	O
of	O
predefined	O
semi-graphical	O
characters	O
usable	O
for	O
drawing	O
boxes	O
and	O
other	O
rudimentary	O
graphics	O
,	O
which	O
can	O
be	O
used	O
to	O
highlight	O
the	O
content	O
or	O
to	O
simulate	O
widget	O
or	O
control	O
interface	O
objects	O
found	O
in	O
GUI	B-Application
programs	O
.	O
</s>
<s>
A	O
typical	O
example	O
is	O
the	O
IBM	O
code	O
page	O
437	O
character	B-General_Concept
set	I-General_Concept
.	O
</s>
<s>
An	O
important	O
characteristic	O
of	O
text	B-Application
mode	I-Application
programs	O
is	O
that	O
they	O
assume	O
monospace	O
fonts	O
,	O
where	O
every	O
character	O
has	O
the	O
same	O
width	O
on	O
screen	O
,	O
which	O
allows	O
them	O
to	O
easily	O
maintain	O
the	O
vertical	O
alignment	O
when	O
displaying	O
semi-graphical	O
characters	O
.	O
</s>
<s>
Depending	O
on	O
the	O
environment	O
,	O
the	O
screen	B-Algorithm
buffer	I-Algorithm
can	O
be	O
directly	B-Architecture
addressable	I-Architecture
.	O
</s>
<s>
Programs	O
that	O
display	O
output	O
on	O
remote	O
video	B-General_Concept
terminals	I-General_Concept
must	O
issue	O
special	O
control	O
sequences	O
to	O
manipulate	O
the	O
screen	B-Algorithm
buffer	I-Algorithm
.	O
</s>
<s>
The	O
most	O
popular	O
standards	O
for	O
such	O
control	O
sequences	O
are	O
ANSI	O
and	O
VT100	B-Device
.	O
</s>
<s>
Programs	O
accessing	O
the	O
screen	B-Algorithm
buffer	I-Algorithm
through	O
control	O
sequences	O
may	O
lose	O
synchronization	O
with	O
the	O
actual	O
display	O
so	O
that	O
many	O
text	B-Application
mode	I-Application
programs	O
have	O
a	O
redisplay	O
everything	O
command	O
,	O
often	O
associated	O
with	O
the	O
key	O
combination	O
.	O
</s>
<s>
Text	B-Application
mode	I-Application
video	O
rendering	O
came	O
to	O
prominence	O
in	O
the	O
early	O
1970s	O
,	O
when	O
video-oriented	O
text	O
terminals	O
started	O
to	O
replace	O
teleprinters	O
in	O
the	O
interactive	O
use	O
of	O
computers	O
.	O
</s>
<s>
The	O
advantages	O
of	O
text	B-Application
modes	I-Application
as	O
compared	O
to	O
graphics	O
modes	O
include	O
lower	O
memory	O
consumption	O
and	O
faster	O
screen	O
manipulation	O
.	O
</s>
<s>
At	O
the	O
time	O
text	O
terminals	O
were	O
beginning	O
to	O
replace	O
teleprinters	O
in	O
the	O
1970s	O
,	O
the	O
extremely	O
high	O
cost	O
of	O
random	B-Architecture
access	I-Architecture
memory	I-Architecture
in	O
that	O
period	O
made	O
it	O
exorbitantly	O
expensive	O
to	O
install	O
enough	O
memory	O
for	O
a	O
computer	O
to	O
simultaneously	O
store	O
the	O
current	O
value	O
of	O
every	O
pixel	B-Algorithm
on	O
a	O
screen	O
,	O
to	O
form	O
what	O
would	O
now	O
be	O
called	O
a	O
framebuffer	B-Algorithm
.	O
</s>
<s>
Early	O
framebuffers	B-Algorithm
were	O
standalone	O
devices	O
which	O
cost	O
tens	O
of	O
thousands	O
of	O
dollars	O
,	O
in	O
addition	O
to	O
the	O
expense	O
of	O
the	O
advanced	O
high-resolution	O
displays	O
to	O
which	O
they	O
were	O
connected	O
.	O
</s>
<s>
For	O
applications	O
that	O
required	O
simple	O
line	O
graphics	O
but	O
for	O
which	O
the	O
expense	O
of	O
a	O
framebuffer	B-Algorithm
could	O
not	O
be	O
justified	O
,	O
vector	B-General_Concept
displays	I-General_Concept
were	O
a	O
popular	O
workaround	O
.	O
</s>
<s>
But	O
there	O
were	O
many	O
computer	O
applications	O
(	O
e.g.	O
,	O
data	O
entry	O
into	O
a	O
database	O
)	O
for	O
which	O
all	O
that	O
was	O
required	O
was	O
the	O
ability	O
to	O
render	O
ordinary	O
text	O
in	O
a	O
quick	O
and	O
cost-effective	O
fashion	O
to	O
a	O
cathode	B-Device
ray	I-Device
tube	I-Device
.	O
</s>
<s>
Text	B-Application
mode	I-Application
avoids	O
the	O
problem	O
of	O
expensive	O
memory	O
by	O
having	O
dedicated	O
display	O
hardware	O
re-render	O
each	O
line	O
of	O
text	O
from	O
characters	O
into	O
pixels	B-Algorithm
with	O
each	O
scan	O
of	O
the	O
screen	O
by	O
the	O
cathode	O
ray	O
.	O
</s>
<s>
In	O
turn	O
,	O
the	O
display	O
hardware	O
needs	O
only	O
enough	O
memory	O
to	O
store	O
the	O
pixels	B-Algorithm
equivalent	O
to	O
one	O
line	O
of	O
text	O
(	O
or	O
even	O
less	O
)	O
at	O
a	O
time	O
.	O
</s>
<s>
Thus	O
,	O
the	O
computer	O
's	O
screen	B-Algorithm
buffer	I-Algorithm
only	O
stores	O
and	O
knows	O
about	O
the	O
underlying	O
text	O
characters	O
(	O
hence	O
the	O
name	O
"	O
text	B-Application
mode	I-Application
"	O
)	O
and	O
the	O
only	O
location	O
where	O
the	O
actual	O
pixels	B-Algorithm
representing	O
those	O
characters	O
exist	O
as	O
a	O
single	O
unified	O
image	O
is	O
the	O
screen	O
itself	O
,	O
as	O
viewed	O
by	O
the	O
user	O
(	O
thanks	O
to	O
the	O
phenomenon	O
of	O
persistence	O
of	O
vision	O
)	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
screen	B-Algorithm
buffer	I-Algorithm
sufficient	O
to	O
hold	O
a	O
standard	O
grid	O
of	O
80	O
by	O
25	O
characters	O
requires	O
at	O
least	O
2,000	O
bytes	O
.	O
</s>
<s>
Assuming	O
a	O
monochrome	B-Device
display	I-Device
,	O
8	O
bits	O
per	O
byte	O
,	O
and	O
a	O
standard	O
size	O
of	O
8	O
times	O
8	O
bits	O
for	O
each	O
character	O
,	O
a	O
framebuffer	B-Algorithm
large	O
enough	O
to	O
hold	O
every	O
pixel	B-Algorithm
on	O
the	O
resulting	O
screen	O
would	O
require	O
at	O
least	O
128,000	O
bits	O
,	O
16,000	O
bytes	O
,	O
or	O
just	O
under	O
16	O
kilobytes	O
.	O
</s>
<s>
By	O
the	O
standards	O
of	O
modern	O
computers	O
,	O
these	O
may	O
seem	O
like	O
trivial	O
amounts	O
of	O
memory	O
,	O
but	O
to	O
put	O
them	O
in	O
context	O
,	O
the	O
original	O
Apple	B-Device
II	I-Device
was	O
released	O
in	O
1977	O
with	O
only	O
four	O
kilobytes	O
of	O
memory	O
and	O
a	O
price	O
of	O
$	O
1,300	O
in	O
U.S.	O
dollars	O
(	O
at	O
a	O
time	O
when	O
the	O
minimum	O
wage	O
in	O
the	O
United	O
States	O
was	O
only	O
$2.30	O
per	O
hour	O
)	O
.	O
</s>
<s>
Another	O
advantage	O
of	O
text	B-Application
mode	I-Application
is	O
that	O
it	O
has	O
relatively	O
low	O
bandwidth	O
requirements	O
in	O
remote	O
terminal	O
use	O
.	O
</s>
<s>
Thus	O
,	O
a	O
text	B-Application
mode	I-Application
remote	O
terminal	O
can	O
necessarily	O
update	O
the	O
screen	O
much	O
faster	O
than	O
a	O
graphics	O
mode	O
remote	O
terminal	O
linked	O
to	O
the	O
same	O
amount	O
of	O
bandwidth	O
(	O
and	O
in	O
turn	O
will	O
seem	O
more	O
responsive	O
)	O
,	O
since	O
the	O
remote	O
server	O
may	O
only	O
need	O
to	O
transmit	O
a	O
few	O
dozen	O
bytes	O
for	O
each	O
screen	O
update	O
in	O
text	B-Application
mode	I-Application
,	O
as	O
opposed	O
to	O
complex	O
raster	O
graphics	O
remote	B-Operating_System
procedure	I-Operating_System
calls	I-Operating_System
that	O
may	O
require	O
the	O
transmission	O
and	O
rendering	O
of	O
entire	O
bitmaps	O
.	O
</s>
<s>
The	O
border	O
between	O
text	B-Application
mode	I-Application
and	O
graphical	O
programs	O
can	O
sometimes	O
be	O
fuzzy	O
,	O
especially	O
on	O
the	O
PC	O
's	O
VGA	B-Protocol
hardware	O
,	O
because	O
many	O
later	O
text	B-Application
mode	I-Application
programs	O
tried	O
to	O
push	O
the	O
model	O
to	O
the	O
extreme	O
by	O
playing	O
with	O
the	O
video	B-Device
controller	I-Device
.	O
</s>
<s>
For	O
example	O
,	O
they	O
redefined	O
the	O
character	B-General_Concept
set	I-General_Concept
in	O
order	O
to	O
create	O
custom	O
semi-graphical	O
characters	O
,	O
or	O
even	O
created	O
the	O
appearance	O
of	O
a	O
graphical	O
mouse	O
pointer	O
by	O
redefining	O
the	O
appearance	O
of	O
the	O
characters	O
over	O
which	O
the	O
mouse	O
pointer	O
was	O
shown	O
at	O
a	O
given	O
time	O
.	O
</s>
<s>
Text	B-Application
mode	I-Application
rendering	O
with	O
user-defined	O
characters	O
has	O
also	O
been	O
useful	O
for	O
2D	O
computer	O
and	O
video	O
games	O
because	O
the	O
game	O
screen	O
can	O
be	O
manipulated	O
much	O
faster	O
than	O
with	O
pixel-oriented	O
rendering	O
.	O
</s>
<s>
A	O
video	B-Device
controller	I-Device
implementing	O
a	O
text	B-Application
mode	I-Application
usually	O
uses	O
two	O
distinct	O
areas	O
of	O
memory	O
.	O
</s>
<s>
Character	O
memory	O
or	O
a	O
pattern	O
table	O
contains	O
a	O
raster	O
font	O
in	O
use	O
,	O
where	O
each	O
character	O
is	O
represented	O
by	O
a	O
dot	B-General_Concept
matrix	I-General_Concept
(	O
a	O
matrix	B-Architecture
of	O
bits	O
)	O
,	O
so	O
the	O
character	O
memory	O
could	O
be	O
considered	O
as	O
a	O
three-dimensional	O
bit	B-Data_Structure
array	I-Data_Structure
.	O
</s>
<s>
Display	O
matrix	B-Architecture
(	O
a	O
text	O
buffer	O
,	O
screen	B-Algorithm
buffer	I-Algorithm
,	O
or	O
nametable	O
)	O
tracks	O
which	O
character	O
is	O
in	O
each	O
cell	O
.	O
</s>
<s>
In	O
the	O
simple	O
case	O
the	O
display	O
matrix	B-Architecture
can	O
be	O
just	O
a	O
matrix	B-Architecture
of	O
code	O
points	O
(	O
so	O
named	O
character	B-Application
pointer	I-Application
table	I-Application
)	O
,	O
but	O
it	O
usually	O
stores	O
for	O
each	O
character	O
position	O
not	O
only	O
a	O
code	O
,	O
but	O
also	O
attributes	O
.	O
</s>
<s>
The	O
glyph	O
is	O
8×8	O
pixels	B-Algorithm
,	O
with	O
3-bit	O
low	O
parts	O
of	O
scan	O
line	O
and	O
dot	O
counter	O
.	O
</s>
<s>
The	O
screen	O
is	O
between	O
20×18	O
and	O
32×32	O
character	B-Application
cells	I-Application
,	O
with	O
5-bit	O
indices	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
raster	O
scan	O
output	O
,	O
which	O
is	O
the	O
most	O
common	O
for	O
computer	B-Device
monitors	I-Device
,	O
the	O
corresponding	O
video	O
signal	O
is	O
made	O
by	O
the	O
character	O
generator	O
,	O
a	O
special	O
electronic	O
unit	O
similar	O
to	O
devices	O
with	O
the	O
same	O
name	O
used	O
in	O
video	O
technology	O
.	O
</s>
<s>
The	O
video	B-Device
controller	I-Device
has	O
two	O
registers	B-General_Concept
:	O
scan	O
line	O
counter	O
and	O
dot	O
counter	O
,	O
serving	O
as	O
coordinates	O
in	O
the	O
screen	O
dot	B-General_Concept
matrix	I-General_Concept
.	O
</s>
<s>
Each	O
of	O
them	O
must	O
be	O
divided	O
by	O
corresponding	O
glyph	O
size	O
to	O
obtain	O
an	O
index	O
in	O
the	O
display	O
matrix	B-Architecture
;	O
the	O
remainder	O
is	O
an	O
index	O
in	O
glyph	O
matrix	B-Architecture
.	O
</s>
<s>
If	O
glyph	O
size	O
equals	O
to	O
2n	O
,	O
then	O
it	O
is	O
possible	O
just	O
to	O
use	O
n	O
low	O
bits	O
of	O
a	O
binary	O
register	O
as	O
an	O
index	O
in	O
glyph	O
matrix	B-Architecture
,	O
and	O
the	O
rest	O
of	O
bits	O
as	O
an	O
index	O
in	O
the	O
display	O
matrix	B-Architecture
—	O
see	O
the	O
scheme	O
.	O
</s>
<s>
The	O
character	O
memory	O
resides	O
in	O
a	O
read-only	B-Device
memory	I-Device
in	O
some	O
systems	O
.	O
</s>
<s>
Other	O
systems	O
allow	O
the	O
use	O
of	O
RAM	B-Architecture
for	O
this	O
purpose	O
,	O
making	O
it	O
possible	O
to	O
redefine	O
the	O
typeface	O
and	O
even	O
the	O
character	B-General_Concept
set	I-General_Concept
for	O
application-specific	O
purposes	O
.	O
</s>
<s>
The	O
use	O
of	O
RAM-based	O
characters	O
also	O
facilitates	O
some	O
special	O
techniques	O
,	O
such	O
as	O
the	O
implementation	O
of	O
a	O
pixel-graphics	O
frame	B-Algorithm
buffer	I-Algorithm
by	O
reserving	O
some	O
characters	O
for	O
a	O
bitmap	O
and	O
writing	O
pixels	B-Algorithm
directly	O
to	O
their	O
corresponding	O
character	O
memory	O
.	O
</s>
<s>
In	O
some	O
historical	O
graphics	O
chips	O
,	O
including	O
the	O
TMS9918	B-Architecture
,	O
the	O
MOS	B-General_Concept
Technology	I-General_Concept
VIC	I-General_Concept
,	O
and	O
the	O
Game	B-Device
Boy	I-Device
graphics	O
hardware	O
,	O
this	O
was	O
actually	O
the	O
canonical	O
way	O
of	O
doing	O
pixel	B-Algorithm
graphics	O
.	O
</s>
<s>
Text	B-Application
modes	I-Application
often	O
assign	O
attributes	O
to	O
the	O
displayed	O
characters	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
VT100	B-Device
terminal	O
allows	O
each	O
character	O
to	O
be	O
underlined	O
,	O
brightened	O
,	O
blinking	O
or	O
inverse	O
.	O
</s>
<s>
Color-supporting	O
devices	O
usually	O
allow	O
the	O
color	O
of	O
each	O
character	O
,	O
and	O
often	O
the	O
background	O
color	O
as	O
well	O
,	O
to	O
be	O
selected	O
from	O
a	O
limited	O
palette	B-Data_Structure
of	O
colors	O
.	O
</s>
<s>
Some	O
text	B-Application
mode	I-Application
implementations	O
also	O
have	O
the	O
concept	O
of	O
line	O
attributes	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
VT100-compatible	O
line	O
of	O
text	O
terminals	O
supports	O
the	O
doubling	O
of	O
the	O
width	O
and	O
height	O
of	O
the	O
characters	O
on	O
individual	O
text	O
lines	O
.	O
</s>
<s>
Depending	O
on	O
the	O
graphics	B-Device
adapter	I-Device
used	O
,	O
a	O
variety	O
of	O
text	B-Application
modes	I-Application
are	O
available	O
on	O
IBM	O
PC	O
compatible	O
computers	O
.	O
</s>
<s>
MDA	B-Device
text	O
could	O
be	O
emphasized	O
with	O
bright	O
,	O
underline	O
,	O
reverse	O
and	O
blinking	O
attributes	O
.	O
</s>
<s>
Video	B-Device
cards	I-Device
in	O
general	O
are	O
backward	O
compatible	O
,	O
i.e.	O
</s>
<s>
EGA	B-Device
supports	O
all	O
MDA	B-Device
and	O
CGA	B-Device
modes	O
,	O
VGA	B-Protocol
supports	O
MDA	B-Device
,	O
CGA	B-Device
and	O
EGA	B-Device
modes	O
.	O
</s>
<s>
By	O
far	O
the	O
most	O
common	O
text	B-Application
mode	I-Application
used	O
in	O
DOS	O
environments	O
,	O
and	O
initial	O
Windows	B-Application
consoles	I-Application
,	O
is	O
the	O
default	O
80	O
columns	O
by	O
25	O
rows	O
,	O
or	O
80×25	O
,	O
with	O
16	O
colors	O
.	O
</s>
<s>
Several	O
programs	O
,	O
such	O
as	O
terminal	B-Application
emulators	I-Application
,	O
used	O
only	O
80×24	O
for	O
the	O
main	O
display	O
and	O
reserved	O
the	O
bottom	O
row	O
for	O
a	O
status	O
bar	O
.	O
</s>
<s>
Two	O
other	O
VGA	B-Device
text	I-Device
modes	I-Device
,	O
80×43	O
and	O
80×50	O
,	O
exist	O
but	O
were	O
very	O
rarely	O
used	O
.	O
</s>
<s>
The	O
40-column	O
text	B-Application
modes	I-Application
were	O
never	O
very	O
popular	O
outside	O
games	O
and	O
other	O
applications	O
designed	O
for	O
compatibility	O
with	O
television	O
monitors	O
,	O
and	O
were	O
used	O
only	O
for	O
demonstration	O
purposes	O
or	O
with	O
very	O
old	O
hardware	O
.	O
</s>
<s>
Character	O
sizes	O
and	O
graphical	O
resolutions	O
for	O
the	O
extended	O
VESA-compatible	O
Super	O
VGA	B-Device
text	I-Device
modes	I-Device
are	O
manufacturer-dependent	O
.	O
</s>
<s>
Also	O
on	O
these	O
display	B-Device
adapters	I-Device
,	O
available	O
colors	O
can	O
be	O
halved	O
from	O
16	O
to	O
8	O
when	O
a	O
second	O
customized	O
character	B-General_Concept
set	I-General_Concept
is	O
employed	O
(	O
giving	O
a	O
total	O
repertoire	O
of	O
512	O
—	O
instead	O
the	O
common	O
256	O
—	O
different	O
graphic	O
characters	O
simultaneously	O
displayed	O
on	O
the	O
screen	O
)	O
.	O
</s>
<s>
S3	O
)	O
supported	O
custom	O
very	O
large	O
text	B-Application
modes	I-Application
,	O
like	O
100×37	O
or	O
even	O
160×120	O
.	O
</s>
<s>
In	O
Linux	B-Application
systems	O
,	O
a	O
program	O
called	O
SVGATextMode	O
is	O
often	O
used	O
with	O
SVGA	O
cards	O
to	O
set	O
up	O
very	O
large	O
console	B-Application
text	B-Application
modes	I-Application
,	O
such	O
as	O
for	O
use	O
with	O
split-screen	O
terminal	O
multiplexers	O
.	O
</s>
<s>
Many	O
modern	O
programs	O
with	O
a	O
graphical	B-Application
interface	I-Application
simulate	O
the	O
display	O
style	O
of	O
text	B-Application
mode	I-Application
programs	O
,	O
notably	O
when	O
it	O
is	O
important	O
to	O
preserve	O
the	O
vertical	O
alignment	O
of	O
text	O
,	O
e.g.	O
,	O
during	O
computer	B-General_Concept
programming	I-General_Concept
.	O
</s>
<s>
There	O
exist	O
also	O
software	O
components	O
to	O
emulate	B-Application
text	B-Application
mode	I-Application
,	O
such	O
as	O
terminal	B-Application
emulators	I-Application
or	O
command	B-Application
line	I-Application
consoles	O
.	O
</s>
<s>
In	O
Microsoft	B-Application
Windows	I-Application
,	O
the	O
Win32	B-Application
console	I-Application
usually	O
opens	O
in	O
emulated	B-Application
,	O
graphical	O
window	O
mode	O
.	O
</s>
<s>
It	O
can	O
be	O
switched	O
to	O
full	O
screen	O
,	O
true	O
text	B-Application
mode	I-Application
and	O
vice	O
versa	O
by	O
pressing	O
the	O
Alt	B-Device
and	O
Enter	B-Device
keys	I-Device
together	O
.	O
</s>
<s>
Linux	B-Application
virtual	B-Application
console	I-Application
operates	O
in	O
text	B-Application
mode	I-Application
.	O
</s>
<s>
Most	O
Linux	B-Application
distributions	O
support	O
several	O
virtual	B-Application
console	I-Application
screens	O
,	O
accessed	O
by	O
pressing	O
Ctrl	B-Device
,	O
Alt	B-Device
and	O
a	O
function	B-Application
key	I-Application
together	O
.	O
</s>
<s>
The	O
AAlib	B-Protocol
open	B-License
source	I-License
library	O
provides	O
programs	O
and	O
routines	O
that	O
specialize	O
in	O
translating	O
standard	O
image	O
and	O
video	O
files	O
,	O
such	O
as	O
PNG	O
and	O
WMV	B-Device
,	O
and	O
displaying	O
them	O
as	O
a	O
collection	O
of	O
ASCII	B-Protocol
characters	I-Protocol
.	O
</s>
<s>
This	O
enables	O
a	O
rudimentary	O
viewing	O
of	O
graphics	O
files	O
on	O
text	B-Application
mode	I-Application
systems	O
,	O
and	O
on	O
text	B-Application
mode	I-Application
web	O
browsers	O
such	O
as	O
Lynx	B-Application
.	O
</s>
