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Appendix B
Character Formation
Serial matrix printers use a moving printhead with pins to form single
characters sequentially along the printed line. Unlike serial matrix printers,
line matrix printers divide every printable line into horizontal dot rows, then
print a dot row of the entire line at every lateral sweep of the shuttle. The IBM
6400 is a line matrix printer.
During each sweep of the shuttle, hammers are activated to print dots at the
required positions in the dot row. When the shuttle reaches the end of a
sweep, it reverses direction, and the paper advances one dot row. The
hammers print the next row of dots as the shuttle sweeps in the opposite
direction, as shown in Figure 74, unless unidirectional printing is chosen.
After a line of characters is printed, the paper advances to the first dot row of
the next print line. This creates a number of blank rows between lines of
characters, depending on the print mode and line spacing you selected.
Dot
Row
1
2
3
4
5
6
Character
7
Line
8
9
* *
10
11
12
1
2
*
Used for lowercase descender only
* *
Used for underline and lowercase descender
302
Direction of shuttle movement
Start
*
Space
1 Hammer
Print Span
Figure 74. Line Matrix Printing
Paper
Advances
Paper
Feed
Paper
Advances
1 Hammer
Print Span
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