Pin Pattern Calculation
You will use the one-line array that you just created to generate a
two-dimensional pattern. This technique results in a significant saving
of memory compared to the method of generating an array that we
used in the last chapter.
Two patterns are used in each pass of the print head. P is the pattern
formed by the seven vertical dots at the start of each print line, and PO
is its black/white reverse image. The program prints the pattern P in
each column that is headed by a black dot. Pattern PO is printed in the
other columns.
The pin patterns are created this way:
140 FOR PASS=0 TO LAST: P=0:
PRINT "PASS";PASS;"OF";LAST
160 FOR DOT=0 TO H
170 IF A(7*PASS+DOT+l)=l THEN P=P+2^(6-DOT)
180 NEXT DOT
190 P0=127-P: IF PASS=LAST THEN P0=P0+1-2^(7-R)
For each pass of the print head (zero to LAST), the program calculates
the pin patterns, seven dots at a time. Line 170 calculates P, and line
190
calculates its complement, PO.
Appendix F discusses problem codes and the P variable.
Adjust the line spacing to match the 7-dot passes:
120 LPRINT CHR$(27)"1";
If this spacing produces slight gaps between rows, adjust it with
CHR$(27)"3"CHR$(20).
The length of the array depends entirely on the variables in line
20.
The following lines adjust the pin patterns (I’ and PO) for the last pass
of the print head if the array length is not a multiple of seven. Add:
130 LAST=INT(C/7): R=C-7*LAST
150 H=6: IF PASS=LAST THEN H=R-1
On the last pass, R represents the number of pins used, and H is set to
one less than the number of pins to be fired.
192
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