Advanced
BIOS
Functions
Note
that
the
actual
character
data
and
attribute
data
are physically separated in
video memory.
With CMD#O,
both
normal
and
auxiliary character codes may be used in the video
memory format. With
CMD#I,
only
normal
character codes may be used.
In the
BIOS Direct
CRT
I/O
function, the available graphic codes have the
following ranges:
OOH
-
FFH:
Normal character code
OOH
-
FFH:
Auxiliary character code
In the
BDOS
Direct
Console
I/O
function, the available codes have the following
ranges:
20H - 7EH: ASCII graphic code for normal character code
20H -
FDH:
Auxiliary character code with ESC sequence
VIDEO
MEMORY
FORMAT
Video
memory
format
is the
format
of
the display
data
area in the video memory.
Each display
data
item consists
of
2 bytes:
display
data
1
first
I
byte
I
I
second
byte
display
data
2
first
I
byte
I
I
second
byte
display
data
3
first
byte
first byte
=
OOH
(normal character code)
I
second
I byte
I
89H (auxiliary character code specifier)
second byte
=
OOH
-
FFH
(character code)
STRING
DATA
FORMAT
...
In
the string
data
format, each display
data
item must be a
normal
character
code.
Display
data
items are one byte long.
6-21
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