High-Order Bit Control - Epson FX Series User Manual

User-defined characters can't be printed with the top 8 pins (the
standard position for most characters). Eight pins can't be used in
defining characters. Here we suggest some ways to work around these
types of problems.

High-order bit control

If you own a seven-bit system, the FX can help you. It gives you
three instructions to let you control the high-order (eighth) bit:
ESCape ">" turns the high-order control and the high-order bit ON
l
ESCape "=" turns the high-order bit OFF
l
ESCape "#" returns the system to normal by turning the high-order
l
control OFF
Note that the eighth bit does not change state automatically-it
remains in the state that you have set until you change it with one of
the other two bit-control codes.
The FX also helps you 7-bit system users by letting you leave the
eighth bit turned on through changes in the ESCape codes. In other
words, adding 128 to any ESCape code will not change its effect. This
means that the low-order sequence for Emphasized print:
CHR$(27)CHR$(69)
and the high-order sequence:
CHR$(27)CHR$">"CHR$(27)CHR$(69)
produce the same result even though for the high-order sequence,
is added to each of the second pair of character-string codes. This
means that when you turn the high-order bit on to handle numbers
between 128 and 255, you do not have to worry about changing any
ESCape code sequences.
Here's an example of how you can use the three codes:
NEW
10 LPRINT CHR$(27)" 'Sets eighth bit
20 FOR X=65 TO 90: LPRINT CHR$(X);: NEXT X
30
LPRINT CHR$(27)"="
40
FOR X=193 TO 218: LPRINT CHR$(X);: NEXT X
50 LPRINT CHR$(27)"#" ' Returns eighth bit to normal
310
'Supresses eighth bit
128