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Now you’ve seen how to design a character by placing dots on a grid
and translating the dots to decimal equivalents. The last step in defining
a character is to send this information to the printer.
Sending information to your printer
The printer loads characters in the print style (Letter Quality, draft, or
proportional) that the printer is currently using. It also records whether
italic, superscript, or subscript is turned on. This means that if you want
to print a character in the italic mode, for example, you must have the
italic mode turned on when you define the character.
The command your printer uses to define characters is one of the most
complex in its repertoire. The format of the command is this:
ESC & 0
nl
n2
do
dl
d2
data
The ESC & is simple enough. The 0 (which is ASCII code 0, not the
numeral zero in quotation marks) allows for future enhancements. At
this time, it is always ASCII 0.
With your printer, you can define many characters with a single
command. The values
nl
and
n2
are the ASCII codes for the first and
last characters you are defining. If you are defining only one character,
nl
and
n2
are the same. You can use any codes between 0 and 127
decimal for
nl
and
n2,
but it is best not to define decimal 32, which is
the code for a space. Also, you can use letters in quotation marks instead
of ASCII numbers for
nl
and
n2.
An example will show you how to specify
nl
and
n2.
If, for instance,
you wanted to redefine the characters A through Z,
nl
would be A (or
ASCII code 65) and
n2
would be Z (or ASCII
code
90). So the command
ESC & 0 AZ (followed by the appropriate data) would replace the entire
alphabet of capital letters.
Following the specification of the range of characters to be defined in this
command are three data bytes (do-&) that specify the width of the
character and the space around it. The left space (in dot columns) is
specified by
do,
and the right space is specified by
dz.
The second byte
(dl)
specifies the number of columns of dots that are printed to make up
Using Software and Graphics
4-27