<s>
Text-based	O
semigraphics	B-Data_Structure
or	O
pseudographics	B-Data_Structure
is	O
a	O
primitive	O
method	O
used	O
in	O
early	O
text	B-Application
mode	I-Application
video	O
hardware	O
to	O
emulate	O
raster	B-Algorithm
graphics	I-Algorithm
without	O
having	O
to	O
implement	O
the	O
logic	O
for	O
such	O
a	O
display	O
mode	O
.	O
</s>
<s>
There	O
are	O
two	O
different	O
ways	O
to	O
accomplish	O
the	O
emulation	O
of	O
raster	B-Algorithm
graphics	I-Algorithm
.	O
</s>
<s>
The	O
first	O
one	O
is	O
to	O
create	O
a	O
low-resolution	O
all	O
points	O
addressable	O
mode	O
using	O
a	O
set	O
of	O
special	O
characters	O
with	O
all	O
binary	O
combinations	O
of	O
a	O
certain	O
subdivision	O
matrix	O
of	O
the	O
text	B-Application
mode	I-Application
character	O
size	O
;	O
this	O
method	O
is	O
referred	O
to	O
as	O
block	O
graphics	O
,	O
or	O
sometimes	O
mosaic	O
graphics	O
.	O
</s>
<s>
The	O
second	O
one	O
is	O
to	O
use	O
special	O
shapes	O
instead	O
of	O
glyphs	B-Application
(	O
letters	O
and	O
figures	O
)	O
that	O
appear	O
as	O
if	O
drawn	O
in	O
raster	B-Algorithm
graphics	I-Algorithm
mode	O
,	O
sometimes	O
referred	O
to	O
as	O
semi	O
-	O
or	O
pseudo-graphics	B-Data_Structure
;	O
an	O
important	O
example	O
of	O
this	O
is	O
box-drawing	O
characters	O
.	O
</s>
<s>
Semigraphical	O
characters	O
(	O
including	O
some	O
block	O
elements	O
)	O
are	O
still	O
incorporated	O
into	O
the	O
BIOS	B-Device
of	O
any	O
VGA	B-Protocol
compatible	O
video	O
card	O
,	O
so	O
any	O
PC	O
can	O
display	O
these	O
characters	O
from	O
the	O
moment	O
it	O
is	O
turned	O
on	O
,	O
even	O
when	O
no	O
operating	O
system	O
is	O
yet	O
loaded	O
.	O
</s>
<s>
Single	O
and	O
double	O
lines	O
are	O
still	O
often	O
drawn	O
with	O
this	O
method	O
when	O
the	O
system	O
uses	O
text	B-Application
mode	I-Application
;	O
for	O
example	O
when	O
running	O
the	O
BIOS	B-Device
setup	O
program	O
.	O
</s>
<s>
But	O
dividing	O
an	O
8×8	O
character	O
in	O
2×2	O
"	O
pixels	O
"	O
called	O
quadrants	O
was	O
also	O
common	O
(	O
it	O
was	O
,	O
for	O
example	O
,	O
used	B-Language
in	I-Language
the	I-Language
Sinclair	I-Language
ZX81	I-Language
)	O
.	O
</s>
<s>
The	O
Galaksija	B-Device
's	I-Device
graphics	O
mode	O
is	O
an	O
example	O
,	O
although	O
with	O
a	O
4:5:4	O
scheme	O
the	O
distortion	O
effect	O
was	O
minimal	O
.	O
</s>
<s>
The	O
seminal	O
use	O
of	O
this	O
technology	O
was	O
in	O
the	O
TRS-80	B-Device
where	O
the	O
only	O
way	O
to	O
get	O
discrete	O
pixels	O
on	O
the	O
screen	O
that	O
could	O
be	O
turned	O
on	O
and	O
off	O
individually	O
,	O
(	O
all	O
points	O
addressable	O
)	O
was	O
by	O
the	O
use	O
of	O
a	O
2×3	O
pixel	O
matrix	O
of	O
block	O
graphics	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
the	O
TRS-80	B-Device
these	O
block	O
graphics	O
were	O
not	O
incorporated	O
into	O
a	O
font	O
ROM	O
,	O
as	O
later	O
became	O
the	O
norm	O
,	O
but	O
were	O
generated	O
directly	O
from	O
the	O
logic	O
pattern	O
of	O
six	O
bits	O
from	O
the	O
video	O
RAM	O
using	O
a	O
dedicated	O
circuit	O
made	O
from	O
logic	O
gates	O
.	O
</s>
<s>
An	O
earlier	O
system	O
using	O
the	O
same	O
pseudo-graphics	B-Data_Structure
array	O
of	O
a	O
2	O
by	O
3	O
matrix	O
was	O
the	O
Video	O
Terminal	O
Interface	O
(	O
VTI	O
)	O
of	O
the	O
Poly-88	O
by	O
polymorphic	O
systems	O
,	O
an	O
S-100	B-Architecture
bus	I-Architecture
based	O
system	O
predating	O
the	O
TRS-80	B-Device
.	O
</s>
<s>
If	O
the	O
system	O
also	O
supported	O
color	O
,	O
the	O
color	O
resolution	O
of	O
the	O
resulting	O
pixels	O
was	O
normally	O
equal	O
to	O
the	O
text	O
resolution	O
,	O
often	O
leading	O
to	O
attribute	B-Algorithm
clash	I-Algorithm
as	O
the	O
color	O
of	O
a	O
pixel	O
could	O
not	O
be	O
changed	O
on	O
a	O
per	O
pixel	O
basis	O
,	O
but	O
only	O
to	O
one	O
"	O
ink	O
"	O
,	O
and	O
one	O
"	O
background	O
"	O
color	O
for	O
all	O
pixels	O
within	O
a	O
character	O
position	O
.	O
</s>
<s>
The	O
assignment	O
in	O
ASCII	B-Protocol
of	O
the	O
rub-out	O
character	O
(	O
to	O
the	O
code	O
point	O
127	O
)	O
led	O
designers	O
of	O
VDUs	O
to	O
use	O
"	O
rub-out	O
"	O
for	O
a	O
character	O
square	O
filled	O
with	O
"	O
ink	O
"	O
,	O
which	O
was	O
often	O
used	O
to	O
represent	O
the	O
cursor	O
.	O
</s>
<s>
The	O
ZX80	B-Operating_System
and	O
ZX81	B-Language
character	I-Language
sets	I-Language
,	O
where	O
a	O
matrix	O
of	O
2×2	O
pixels	O
was	O
used	O
,	O
with	O
the	O
space	O
and	O
invert	O
attribute	O
tricks	O
to	O
keep	O
the	O
number	O
of	O
characters	O
in	O
the	O
ROM	O
needed	O
down	O
to	O
just	O
7	O
(	O
of	O
the	O
necessary	O
16	O
)	O
.	O
</s>
<s>
The	O
ZX	B-Operating_System
Spectrum	I-Operating_System
also	O
supported	O
block	O
graphics	O
as	O
well	O
as	O
"	O
real	O
"	O
higher-resolution	O
graphics	O
.	O
</s>
<s>
Other	O
systems	O
that	O
used	O
a	O
2×2	O
matrix	O
were	O
the	O
Panasonic	B-Device
JR-200	I-Device
and	O
the	O
Mattel	B-Device
Aquarius	I-Device
.	O
</s>
<s>
The	O
Commodore	B-Device
PET	I-Device
also	O
had	O
a	O
few	O
characters	O
to	O
support	O
2×2	O
text	B-Data_Structure
semigraphics	I-Data_Structure
in	O
its	O
PETSCII	B-Protocol
character	O
set	O
.	O
</s>
<s>
The	O
TRS-80	B-Device
Color	I-Device
Computer	I-Device
,	O
and	O
the	O
Dragon	B-Device
32/64	I-Device
are	O
good	O
examples	O
of	O
systems	O
using	O
2×2	O
matrix	O
color	O
semigraphics	B-Data_Structure
.	O
</s>
<s>
But	O
their	O
Motorola	B-General_Concept
6847	I-General_Concept
VDC	B-General_Concept
also	O
supported	O
a	O
little	O
used	O
6-block	O
semigraphics	B-Data_Structure
mode	O
.	O
</s>
<s>
Videotex	B-Operating_System
and	O
teletext	O
systems	O
used	O
a	O
2×3	O
matrix	O
and	O
one	O
foreground	O
(	O
"	O
ink	O
"	O
)	O
,	O
and	O
one	O
background	O
color	O
,	O
normally	O
out	O
of	O
a	O
set	O
of	O
eight	O
colors	O
(	O
including	O
black	O
and	O
white	O
)	O
.	O
</s>
<s>
Many	O
systems	O
used	O
"	O
Videotex	B-Device
graphics	I-Device
"	O
.	O
</s>
<s>
One	O
of	O
the	O
best	O
known	O
examples	O
is	O
the	O
Acorn	B-Device
BBC	I-Device
Micro	I-Device
's	O
default	O
graphics	O
mode	O
(	O
mode	O
7	O
)	O
.	O
</s>
<s>
Other	O
systems	O
which	O
used	O
"	O
Videotex	B-Operating_System
"	O
-like	O
graphics	O
are	O
:	O
the	O
ABC	B-Device
80	I-Device
,	O
the	O
Grundy	B-Device
NewBrain	I-Device
,	O
many	O
of	O
the	O
Acorn	B-Device
Eurocard	I-Device
systems	I-Device
,	O
and	O
the	O
Philips	B-Device
P2000T	I-Device
,	O
which	O
actually	O
used	O
a	O
Teletext	O
chip	O
designed	O
for	O
their	O
TV	O
's	O
.	O
</s>
<s>
The	O
Matra	B-Device
Alice	I-Device
32	O
,	O
Matra	B-Device
Alice	I-Device
90	O
and	O
Philips	B-Device
VG5000	I-Device
were	O
based	O
on	O
the	O
Thomson	B-General_Concept
EF9345	I-General_Concept
graphic	B-General_Concept
chip	I-General_Concept
,	O
only	O
capable	O
of	O
displaying	O
alphanumeric	O
and	O
semigraphic	B-Data_Structure
characters	O
.	O
</s>
<s>
The	O
PC-8001	B-Device
managed	O
to	O
combine	O
normal	O
text	O
with	O
a	O
full	O
set	O
of	O
256	O
text	O
semigraphical	O
"	O
characters	O
"	O
in	O
a	O
2×4	O
matrix	O
;	O
how	O
the	O
system	O
distinguished	O
the	O
8	O
bits	O
used	O
for	O
"	O
normal	O
"	O
fonts	O
from	O
the	O
8	O
bits	O
needed	O
for	O
the	O
text	B-Data_Structure
semigraphics	I-Data_Structure
is	O
unclear	O
.	O
</s>
<s>
One	O
of	O
the	O
last	O
video	O
systems	O
where	O
text	B-Data_Structure
semigraphics	I-Data_Structure
were	O
a	O
useful	O
option	O
was	O
the	O
Color	B-Device
Graphics	I-Device
Adapter	I-Device
(	O
CGA	B-Device
)	O
.	O
</s>
<s>
This	O
graphics	O
adapter	O
for	O
early	O
IBM-PCs	B-Device
only	O
supported	O
four	O
colors	O
in	O
its	O
high-resolution	O
graphics	O
mode	O
,	O
but	O
in	O
text	B-Application
mode	I-Application
it	O
could	O
display	O
16	O
different	O
colors	O
.	O
</s>
<s>
Although	O
the	O
CGA	B-Device
adapter	O
's	O
font	O
ROM	O
did	O
not	O
contain	O
all	O
of	O
the	O
otherwise	O
typical	O
text	B-Data_Structure
semigraphics	I-Data_Structure
characters	O
,	O
it	O
was	O
still	O
possible	O
to	O
create	O
a	O
160	O
×	O
100	O
CGA	B-Device
text	B-Data_Structure
semigraphics	I-Data_Structure
mode	O
using	O
a	O
semi-documented	O
trick	O
.	O
</s>
<s>
Semigraphical	O
characters	O
are	O
also	O
characters	O
in	O
a	O
font	O
that	O
are	O
intended	O
to	O
give	O
the	O
impression	O
that	O
a	O
system	O
can	O
support	O
high	O
resolution	O
graphics	O
,	O
while	O
in	O
fact	O
the	O
system	O
operates	O
in	O
text	B-Application
mode	I-Application
.	O
</s>
<s>
One	O
of	O
the	O
first	O
systems	O
that	O
used	O
such	O
characters	O
,	O
the	O
canonical	O
example	O
that	O
others	O
followed	O
,	O
was	O
the	O
Commodore	B-Device
PET	I-Device
,	O
which	O
had	O
many	O
of	O
them	O
within	O
its	O
PETSCII	B-Protocol
font	O
set	O
.	O
</s>
<s>
Another	O
good	O
example	O
of	O
a	O
system	O
that	O
relied	O
on	O
semigraphical	O
characters	O
is	O
the	O
venerable	O
Sharp	B-Operating_System
MZ80K	I-Operating_System
,	O
which	O
had	O
no	O
high-resolution	O
graphics	O
,	O
nor	O
reprogrammable	O
characters	O
,	O
but	O
relied	O
fully	O
on	O
an	O
extended	O
font	O
set	O
with	O
many	O
pseudo	O
graphical	O
characters	O
.	O
</s>
<s>
Some	O
of	O
the	O
systems	O
that	O
had	O
a	O
programmable	O
font	O
set	O
,	O
but	O
did	O
not	O
have	O
a	O
real	O
high	O
resolution	O
raster	B-Algorithm
graphics	I-Algorithm
hardware	O
,	O
came	O
with	O
default	O
character	O
sets	O
to	O
be	O
uploaded	O
in	O
character	O
set	O
RAM	O
,	O
and	O
these	O
sets	O
often	O
incorporated	O
the	O
ideas	O
mentioned	O
here	O
,	O
although	O
it	O
was	O
often	O
also	O
the	O
case	O
that	O
dedicated	O
semigraphical	O
characters	O
were	O
defined	O
as	O
needed	O
.	O
</s>
<s>
The	O
original	O
IBM	B-Device
PC	I-Device
with	O
the	O
MDA	B-Device
offered	O
no	O
form	O
of	O
graphics	O
other	O
than	O
the	O
box-drawing	O
characters	O
of	O
its	O
default	O
hardware	O
code	O
page	O
437	O
.	O
</s>
<s>
The	O
Commodore	B-Device
PET	I-Device
was	O
one	O
of	O
the	O
first	O
systems	O
to	O
rely	O
heavily	O
on	O
semigraphical	O
characters	O
,	O
to	O
get	O
any	O
form	O
of	O
graphics	O
on	O
screen	O
(	O
see	O
PETSCII	B-Protocol
)	O
.	O
</s>
<s>
The	O
Sinclair	B-Operating_System
ZX80	I-Operating_System
and	O
ZX81	O
relied	O
on	O
block	O
graphics	O
characters	O
for	O
a	O
low-resolution	O
graphics	O
of	O
64×48	O
pixels	O
black-and-white	O
or	O
32×48	O
in	O
black	O
,	O
white	O
,	O
and	O
dithered	O
gray	O
as	O
seen	O
in	O
the	O
ZX80	B-Language
character	I-Language
set	I-Language
and	O
ZX81	B-Language
character	I-Language
set	I-Language
.	O
</s>
<s>
The	O
Mattel	B-Device
Aquarius	I-Device
relied	O
completely	O
on	O
its	O
character	O
set	O
for	O
games	O
,	O
even	O
though	O
it	O
was	O
marketed	O
through	O
toy-shops	O
.	O
</s>
<s>
It	O
never	O
became	O
a	O
commercial	O
success	O
partly	O
because	O
of	O
this	O
limitation	O
,	O
which	O
was	O
outdated	O
at	O
the	O
time	O
(	O
see	O
Mattel	B-Device
Aquarius	I-Device
character	I-Device
set	I-Device
)	O
.	O
</s>
<s>
The	O
Panasonic	B-Device
JR-200	I-Device
also	O
used	O
semigraphical	O
characters	O
in	O
combination	O
with	O
block	O
graphics	O
(	O
see	O
Matsushita	O
JR	O
series	O
character	O
set	O
)	O
.	O
</s>
<s>
The	O
Sharp	B-Operating_System
MZ	I-Operating_System
series	O
of	O
computers	O
offered	O
no	O
high	O
resolution	O
or	O
programmable	O
characters	O
,	O
but	O
did	O
have	O
a	O
very	O
complete	O
set	O
of	O
semigraphical	O
characters	O
(	O
see	O
Sharp	B-Operating_System
MZ	I-Operating_System
character	O
set	O
)	O
.	O
</s>
<s>
The	O
Matra	B-Device
Alice	I-Device
32	O
and	O
90	O
;	O
and	O
the	O
Philips	B-Device
VG5000	I-Device
(	O
see	O
Thomson	B-General_Concept
EF9345	I-General_Concept
character	O
set	O
)	O
.	O
</s>
<s>
The	O
Compukit	B-Device
UK101	I-Device
(	O
clone	O
of	O
the	O
popular	O
Ohio	O
Scientific	O
superboard	O
)	O
also	O
was	O
a	O
very	O
early	O
system	O
that	O
relied	O
on	O
its	O
256	O
characters	O
set	O
.	O
</s>
<s>
The	O
text	B-Application
modes	I-Application
of	O
later	O
Apple	O
II	O
computers	O
,	O
beginning	O
with	O
the	O
Apple	O
IIc	O
and	O
the	O
enhanced	O
version	O
of	O
the	O
Apple	B-Device
IIe	I-Device
,	O
supported	O
the	O
MouseText	B-Device
character	O
set	O
,	O
which	O
replaced	O
flashing	O
uppercase	O
characters	O
when	O
enabled	O
.	O
</s>
<s>
Although	O
these	O
Apple	O
systems	O
did	O
not	O
rely	O
on	O
these	O
character	O
sets	O
they	O
did	O
play	O
a	O
role	O
in	O
simulating	O
GUI	O
like	O
graphics	O
of	O
their	O
more	O
advanced	O
family	O
members	O
,	O
while	O
still	O
in	O
text	B-Application
mode	I-Application
.	O
</s>
