User-defined Characters

Run the program to see the printout below:

As you can see, both sets of characters (the original ROM characters that the printer normally uses and the user-defined character set) remain in the printer available for your use. The command to switch between the two sets is used in line 90 and

110. It is:

ESC % n

If n is equal to 0, the normal ROM character set is selected (this is the default). If n is equal to 1, the user-defined character set is selected. If you select the user-defined character set before you have defined any characters, the command is ignored and the ROM characters will still be in use.

You may switch between character sets at any time - even in the middle of a line. To try it, place semicolons at the end of lines 80 and 100 in the program above.

Copying ROM characters to RAM

After running the program above, if you select the user-defined character set and try to print other characters, the only one that will print is the arrow. Since no other characters are in the printer’s user-defined RAM area, nothing else prints. Other characters sent to the printer do not even print as spaces; it is as if they were not sent at all.

In many cases, you may want to redefine only a few of the characters to suit your needs; the rest of the alphabet will work fine as it is. As you have seen, it is possible to switch back and forth at will between the normal character set and the user-defined character set. It is, however, rather inconvenient.

4-28 Software and Graphics