Now wewill calculate the vertical numerical values of the columns of dots,
andenter them underneath the grid.Each vertical column isfirst dividedinto
three groups of eight dots. Each group of eight dots is represented by one
byte. which consistsof eight bits.
Thisis where the numbers down the left sideof the grid come in. Notice that
there is anumber for each row of dots and that each number is twice the
numberbelow it. By making these numbers powers of two we can take any
combination of dots in averticalcolumn and assign them aunique value.
Assigning the Index Table data
Unlikedefining in the Standard mode, you must assign theIndex Table with
the IBM mode. This Index Table is prepared for the information of each
charactersattribute data, 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 9index table data.
Thefirst and the second bytes (m] andm2) indicates the position of the first
dotpattern in the memory. ml is thehigh order byte. and m2 is thelow order
byte.
Thethird byte,m3, indicatesthe charactertype andthe dotpattern datawidth
in the memory.
If the character is normal. simply enter the width of dot pattern in the
memory. If the character is ablock graphic. add 128to the width of dot
pattern in the memory.
Ourtelephone symbol is anormal character and the width of the dot pattern
inthe memory should be 25, so this value is 25.
The fourth byte, m4, indicatesthe printing attribute.
Thisbyte indicates the character width to be printed, and information of the
repetition dots for block graphics characters.
If the character is anormal character, add 192to the character width.
Ifthe character is ablock character, and it should be printed as aline draw
character, add 64 to the character width. Ifthe block character is not aline
draw character, thisbyte should be the same as the character width.
Ourtelephone symbolis anormalpicacharacter. so thecharacter width is 35,
and thisbyte should be 227.
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