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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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