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After you have written the compression mask bit data, line up all the
character data for the compression mask bit that requires “O”.The telephone
symbol looks like Figure 9-5.
F 9 C c p t symbol.
Now we calculate the vertical numerical values of the columns of dots, and
enter them underneath the grid. Each vertical column is first divided into
three groups of eight dots. Each group of eight dots is represented by one
byte, which consists of eight bits.
That’s where the numbers down the left side of the grid come in. Notice that
there is a number for each row of dots and that each number is twice the
number below it. By making these nu’rnberspowers of two we can take any
combination of dots in a vertical column and assign them a unique value.
Assigning the Index Table data
Unlike defining in the Standard mode, you must assigntheIndex Table in the
IBM mode.
This Index Table isprepared for the attribute data of each character, such as
character type (Normal 24-dot high, or 30-dot high block graphics), the dot
pattern data in the memory, and the compression mask bit data.
Each character requires 9 index table data.
The first and the second bytes (ml and rn2) indicate the position of the first
dot pattern in the memory. the high order byte, and m2 isthe low order
byte.