Chapter
6:
Graphics
193
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The 8 X 8 format was chosen because each row
of
the character
conveniently fits into one byte
of
memory, and the eight rows make a nice
round number in the computer's binary number system. This format also
greatly simplifies custom character design. You can
layout
your character
on
an
ordinary sheet
of
graph paper and easily convert a row to its value and
location in character memory.
The eight bytes
that
make up the rows
of
a character are stored next to
. each other in character memory, with the top row first. Each
dot
on a row
corresponds
to
one bit, with the bit for the leftmost
dot
having the highest
binary value,
128.
A bit value
of
1 means the
dot
is
"on"
(displayed in the
character color). A value
of
0 means the
dot
is
"off" (displayed in the screen
color). This
is
what the letter
"A"
looks like in character memory.
Displayed Dots
Binary
Decimal
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00011000
24
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00100100
36
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01000010
66
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01111110
126
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01000010
66
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01000010
66
# #
01000010
66
00000000 0
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