User-defined Characters

Now you have 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 or script (either 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 d0 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 singl e command. The values nl and n2 are the ASCII codes of the first and last characters you are defining. If you are defining only one character, n1 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 0 to 32, which are the codes for control codes. Also, you can use letters in quotation marks instead of ASCII numbers for nl and n2.

Software and Graphics 4-25