80
fired by a different number. One byte of data (a decimal number
from 0 to 255) can thus represent a unique combination of dots.
For example, if the data representing “1” was sent to the print
head, only the bottom pin would fire; if “2” was sent, only the
second pin from the bottom would fire, and if “3” was sent, the
two bottom pins would fire, and so on. Columns of these dots
side by side make all the characters.
0.0. : . : :- 0.0. 0 : . 0 00 0 .a.. .... :- 0 l m.0
0
Figure 6- 1. As the print head moves across the page, each of the
pins prints a row of dots.
DESIGNING YOUR OWN CHARACTERS
Standard characters are permanently stored in the printer’s
ROM (Read Only Memory), but characters you design are
downloaded and stored in RAM (Random Access Memory) for
use.
Designing and printing your own characters has two re-
quirements: firstly, designing the shape of the character,
calculating the data necessary to make the shape, and sending
that data to the printer, and secondary, sending the command to
print the downloaded characters instead of the standard
characters. There are a number of design construints for
download draft quality characters:
l The matrix or grid on which you design the characters is