<s>
The	O
Monochrome	B-Device
Display	I-Device
Adapter	I-Device
(	O
MDA	B-Device
,	O
also	O
MDA	B-Device
card	I-Device
,	O
Monochrome	B-Device
Display	I-Device
and	I-Device
Printer	I-Device
Adapter	I-Device
,	O
MDPA	O
)	O
is	O
IBM	O
's	O
standard	O
video	B-Device
display	I-Device
card	I-Device
and	O
computer	O
display	O
standard	O
for	O
the	O
IBM	B-Device
PC	I-Device
introduced	O
in	O
1981	O
.	O
</s>
<s>
The	O
MDA	B-Device
does	O
not	O
have	O
any	O
pixel-addressable	O
graphics	O
modes	O
,	O
only	O
a	O
single	O
monochrome	O
text	B-Application
mode	I-Application
which	O
can	O
display	O
80	O
columns	O
by	O
25	O
lines	O
of	O
high	O
resolution	O
text	O
characters	B-Data_Structure
or	I-Data_Structure
symbols	I-Data_Structure
useful	I-Data_Structure
for	I-Data_Structure
drawing	I-Data_Structure
forms	I-Data_Structure
.	O
</s>
<s>
The	O
original	O
IBM	B-Device
MDA	I-Device
was	O
an	O
8-bit	O
ISA	B-Architecture
card	I-Architecture
with	O
a	O
Motorola	B-General_Concept
6845	I-General_Concept
display	O
controller	O
,	O
4	O
KB	O
of	O
RAM	B-Architecture
,	O
a	O
DE-9	B-Protocol
output	I-Protocol
port	I-Protocol
intended	O
for	O
use	O
with	O
an	O
IBM	B-Device
monochrome	I-Device
monitor	I-Device
,	O
and	O
a	O
parallel	B-Device
port	I-Device
for	O
attachment	O
of	O
a	O
printer	O
,	O
avoiding	O
the	O
need	O
to	O
purchase	O
a	O
separate	O
card	O
.	O
</s>
<s>
The	O
MDA	B-Device
was	O
based	O
on	O
the	O
IBM	B-Device
System/23	I-Device
Datamaster	I-Device
's	O
display	O
system	O
,	O
and	O
was	O
intended	O
to	O
support	O
business	O
and	O
word	B-General_Concept
processing	I-General_Concept
use	O
with	O
its	O
sharp	O
,	O
high-resolution	O
characters	O
.	O
</s>
<s>
Each	O
character	O
is	O
rendered	O
in	O
a	O
box	O
of	O
9×14	O
pixels	B-Algorithm
,	O
of	O
which	O
7×11	O
depicts	O
the	O
character	O
itself	O
and	O
the	O
other	O
pixels	B-Algorithm
provide	O
space	O
between	O
character	O
columns	O
and	O
lines	O
.	O
</s>
<s>
Some	O
characters	O
,	O
such	O
as	O
the	O
lowercase	O
"	O
m	O
"	O
,	O
are	O
rendered	O
eight	O
pixels	B-Algorithm
across	O
.	O
</s>
<s>
The	O
theoretical	O
total	O
screen	O
display	B-General_Concept
resolution	I-General_Concept
of	O
the	O
MDA	B-Device
is	O
720×350	O
pixels	B-Algorithm
,	O
if	O
the	O
dimensions	O
of	O
all	O
character	B-Application
cells	I-Application
are	O
added	O
up	O
,	O
but	O
the	O
MDA	B-Device
cannot	O
address	O
individual	O
pixels	B-Algorithm
to	O
take	O
full	O
advantage	O
of	O
this	O
resolution	O
.	O
</s>
<s>
Each	O
character	B-Application
cell	I-Application
can	O
be	O
set	O
to	O
one	O
of	O
256	O
bitmap	O
characters	O
stored	O
in	O
ROM	B-Device
on	O
the	O
card	O
,	O
and	O
this	O
character	O
set	O
cannot	O
be	O
altered	O
from	O
the	O
built-in	O
hardware	O
code	O
page	O
437	O
.	O
</s>
<s>
The	O
only	O
way	O
to	O
simulate	O
"	O
graphics	O
"	O
is	O
through	O
ASCII	B-Protocol
art	O
,	O
obtaining	O
a	O
low	O
resolution	O
80×25	O
"	O
pixels	B-Algorithm
"	O
screen	O
,	O
based	O
on	O
character	O
positions	O
.	O
</s>
<s>
Code	O
page	O
437	O
has	O
256	O
characters	O
(	O
0-255	O
)	O
,	O
including	O
the	O
standard	O
95	O
printable	O
ASCII	B-Protocol
characters	I-Protocol
from	O
(	O
32-126	O
)	O
,	O
and	O
the	O
33	O
ASCII	B-Protocol
control	O
codes	O
(	O
0-31	O
and	O
127	O
)	O
are	O
replaced	O
with	O
printable	O
graphic	O
symbols	O
.	O
</s>
<s>
These	O
are	O
invisible	O
,	O
underline	O
,	O
normal	O
,	O
bright	O
(	O
bold	O
)	O
,	O
reverse	B-General_Concept
video	I-General_Concept
,	O
and	O
blinking	O
.	O
</s>
<s>
Reverse	B-General_Concept
video	I-General_Concept
swaps	O
the	O
foreground	O
and	O
background	O
colors	O
,	O
while	O
blinking	O
causes	O
text	O
to	O
flash	O
periodically	O
.	O
</s>
<s>
Early	O
versions	O
of	O
the	O
MDA	B-Device
board	O
have	O
hardware	O
capable	O
of	O
outputting	O
red	O
,	O
green	O
and	O
blue	O
TTL	B-General_Concept
signals	I-General_Concept
on	O
the	O
normally	O
unconnected	O
DE-9	B-Protocol
video	I-Protocol
connector	I-Protocol
pins	O
,	O
theoretically	O
allowing	O
an	O
8-color	O
display	O
with	O
a	O
suitable	O
monitor	O
.	O
</s>
<s>
The	O
MDA	B-Device
was	O
released	O
alongside	O
the	O
IBM	B-Device
Color	I-Device
Graphics	I-Device
Adapter	I-Device
,	O
and	O
in	O
fact	O
could	O
be	O
installed	O
alongside	O
the	O
CGA	B-Device
in	O
the	O
same	O
computer	O
.	O
</s>
<s>
A	O
command	O
included	O
with	O
PC	O
DOS	O
permitted	O
switching	O
the	O
primary	O
display	O
between	O
the	O
CGA	B-Device
and	O
MDA	B-Device
cards	I-Device
.	O
</s>
<s>
Because	O
of	O
the	O
lack	O
of	O
pixel-addressable	O
graphics	O
,	O
MDA	B-Device
owners	O
were	O
unable	O
to	O
play	O
PC	O
games	O
released	O
with	O
graphics	O
support	O
.	O
</s>
<s>
However	O
,	O
textmode	B-Application
games	I-Application
were	O
released	O
for	O
the	O
PC	O
(	O
including	O
text	O
adventures	O
)	O
and	O
at	O
least	O
one	O
game	O
,	O
IBM	O
's	O
One	O
Hundred	O
And	O
One	O
Monochrome	O
Mazes	O
,	O
requires	O
MDA	B-Device
.	O
</s>
<s>
Box-drawing	O
characters	O
made	O
the	O
production	O
of	O
rudimentary	O
graphics	O
practical	O
for	O
early	O
PC	O
game	O
titles	O
,	O
including	O
BBS	B-Protocol
door	I-Protocol
games	I-Protocol
or	O
titles	O
such	O
as	O
Castle	B-Application
Adventure	I-Application
.	O
</s>
<s>
Another	O
use	O
for	O
the	O
MDA	B-Device
was	O
as	O
a	O
secondary	O
display	O
for	O
debugging	O
.	O
</s>
<s>
Applications	O
like	O
SoftICE	B-Application
and	O
the	O
Windows	O
debugger	O
permitted	O
the	O
simultaneous	O
use	O
of	O
an	O
MDA	B-Device
and	O
another	O
graphics	B-Device
card	I-Device
,	O
with	O
the	O
MDA	B-Device
displaying	O
a	O
debugger	O
interface	O
while	O
the	O
other	O
card	O
was	O
showing	O
the	O
primary	O
display	O
.	O
</s>
<s>
A	O
typical	O
8-bit	O
monochrome	O
card	O
could	O
turn	O
the	O
16-bit	O
8	O
MHz	O
ISA	B-Architecture
bus	I-Architecture
into	O
an	O
8-bit	O
4	O
MHz	O
PC	B-General_Concept
bus	I-General_Concept
,	O
which	O
resulted	O
in	O
having	O
the	O
bus	O
bandwidth	O
cut	O
by	O
up	O
to	O
75%	O
.	O
</s>
<s>
If	O
the	O
monochrome	O
card	O
was	O
added	O
to	O
the	O
PC	O
as	O
a	O
second	O
card	O
besides	O
a	O
normal	O
VGA	B-Protocol
card	I-Protocol
for	O
debugging	O
purposes	O
,	O
this	O
resulted	O
in	O
slow	O
VGA	B-Protocol
performance	O
.	O
</s>
<s>
Microsoft	O
recommended	O
in	O
its	O
"	O
Writing	O
HOT	O
Games	O
for	O
Microsoft®	O
Windows™	O
The	O
Microsoft	O
Game	O
Developers’	O
Handbook	O
"	O
to	O
remove	O
the	O
monochrome	O
card	O
in	O
such	O
a	O
setup	O
for	O
maximum	O
speed	O
of	O
the	O
VGA	B-Protocol
card	I-Protocol
.	O
</s>
<s>
The	O
author	O
of	O
an	O
internal	O
IBM	O
publication	O
stated	O
in	O
October	O
1981	O
that	O
he	O
had	O
planned	O
to	O
purchase	O
the	O
CGA	B-Device
adapter	O
but	O
changed	O
his	O
mind	O
after	O
seeing	O
its	O
poor	O
display	O
quality	O
.	O
</s>
<s>
Describing	O
MDA	B-Device
as	O
beautiful	O
,	O
he	O
observed	O
that	O
"	O
you	O
stare	O
at	O
text	O
a	O
whole	O
lot	O
more	O
than	O
you	O
stare	O
at	O
color	O
graphics	O
"	O
.	O
</s>
<s>
MDA	B-Device
was	O
more	O
popular	O
than	O
CGA	B-Device
for	O
business	O
applications	O
.	O
</s>
<s>
The	O
higher	O
resolution	O
of	O
MDA	B-Device
's	O
text	O
and	O
inclusion	O
of	O
a	O
printer	B-Device
port	I-Device
made	O
it	O
more	O
appealing	O
for	O
the	O
business	O
applications	O
that	O
were	O
the	O
focus	O
of	O
the	O
original	O
PC	O
.	O
</s>
<s>
A	O
well	O
known	O
example	O
was	O
the	O
Hercules	B-Device
Graphics	I-Device
Card	I-Device
.	O
</s>
<s>
Introduced	O
in	O
1982	O
,	O
it	O
offered	O
both	O
an	O
MDA-compatible	O
high	O
resolution	O
text	B-Application
mode	I-Application
and	O
a	O
monochrome	O
graphics	O
mode	O
.	O
</s>
<s>
The	O
founder	O
of	O
Hercules	O
Computer	O
Technology	O
,	O
Van	O
Suwannukul	O
,	O
created	O
the	O
Hercules	B-Device
Graphics	I-Device
Card	I-Device
so	O
that	O
he	O
could	O
work	O
on	O
his	O
doctoral	O
thesis	O
on	O
an	O
IBM	B-Device
PC	I-Device
using	O
the	O
Thai	O
alphabet	O
,	O
which	O
was	O
impossible	O
at	O
the	O
low	O
resolution	O
of	O
CGA	B-Device
or	O
the	O
fixed	O
character	O
set	O
of	O
MDA	B-Device
.	O
</s>
<s>
It	O
could	O
address	O
individual	O
pixels	B-Algorithm
,	O
and	O
displayed	O
a	O
black	O
and	O
white	O
picture	O
of	O
720×348	O
pixels	B-Algorithm
.	O
</s>
<s>
This	O
resolution	O
was	O
superior	O
to	O
the	O
CGA	B-Device
card	O
,	O
yet	O
offered	O
pixel-addressable	O
graphics	O
,	O
so	O
despite	O
lacking	O
color	O
capability	O
,	O
the	O
Hercules	O
adapter	O
's	O
offer	O
of	O
high	O
resolution	O
bitmap	O
graphics	O
combined	O
with	O
MDA-grade	O
text	O
quality	O
made	O
it	O
a	O
popular	O
choice	O
,	O
which	O
was	O
even	O
shipped	O
with	O
many	O
clones	B-General_Concept
.	O
</s>
<s>
MDA	B-Device
cards	I-Device
used	O
a	O
DE-9	B-Protocol
output	I-Protocol
port	I-Protocol
intended	O
for	O
a	O
digital	O
TTL	B-General_Concept
monitor	O
,	O
like	O
the	O
IBM	B-Device
monochrome	I-Device
monitor	I-Device
.	O
</s>
<s>
Other	O
boards	O
offer	O
MDA	B-Device
compatibility	B-Device
,	O
although	O
with	O
differences	O
on	O
how	O
attributes	O
are	O
displayed	O
or	O
the	O
font	O
used	O
.	O
</s>
