Preparation
DIP switch
1-4
controls the use of the FX’s
2K
RAM buffer. You can
use this RAM memory as a large text buffer to smooth printer/com-
puter communications, or you can store in it a set of user-defined
characters. Unfortunately, it can’t serve both purposes simultane-
ously. In this and succeeding chapters, we’ll use this RAM area for
user-defined characters. So set switch 1-4 off before proceeding.
Character Definition
Characters are defined with the ESCape "&" command sequence.
The format is:
LPRINT CHR$(27)"&"CHR$(r)CHR$(c
1
)CHR$(c
2
);
The r tells the printer in which RAM area the characters are to be
stored. With a stock printer, there is only one area available: RAM
area 0.
The notations c
1
and c
2
specify the range of characters to be defined.
You can use the entire range of ASCII numbers from 0 to 255 (for
which the ROM characters are shown in Appendix A), except for
those areas where control codes reside (0 to
31, 127
to
159,
and
255).
You can also use some of the control-code locations, but only after
special ESCape codes are issued. We’ll get to that a bit later.
Here’s how c
1
and c
2
work. Suppose you want to redefine the letters
from A to E. The associated ASCII numbers are 65 to 69, so you
simply let c
1
be 65(A) and c
2
be 69(E). Any of the keyboard characters
can be redefined in a similar manner. For example, defining c
1
as 97
and c
2
as
101
selects lowercase letters a through e; defining c
1
as 33 and
c
z
as 43 selects the symbols ! through + .
To simplify things a bit, the ASCII symbols can be used in place of
CHR$(c
1
) and CHR$(c
2
). For example, either:
LPRINT CHR$(27)"&"CHR$(0)CHR$(65)CHR$(69);
or:
LPRINT CHR$(27)"&"CHR$(0)"AE";
selects characters A through E. On some occasions you may wish to
define only one character. That’s O.K., too. Just use the same number
or letter for c
1
and c
2
:
130 LPRINT CHR$(27)"&"CHRS(0)"EE";
200
