Basic Basics - Epson FX-80 User Manual

BASIC basics or ... It's not your printer's fault!
If you ended up with a roman A:
PI
(instead of the one in italics), pay close attention to the following.
The original ASCII code was designed to use the decimal numbers 0
through 127. Computer systems designers soon decided to extend this
range (to 0 through 255) in order to make room for more features.
Unfortunately, some designers did not anticipate that printers would
make use of this extended range. So they designed the BASIC lan-
guage (actually the printer driver) to intercept any number in the up-
per half of the range (128 to 255) and automatically convert it to the
lower half of the range by subtracting 128. In these systems, the code
CHR$(193), for instance, never makes it to the printer. It arrives as a
CHR$(65): 193-128
=
65.
For many applications, you don't need the upper half of the ASCII
codes. For others, the inability to generate codes greater than 127 is a
severe handicap. It is good to be aware of the problem right from the
beginning. Apple users and those of you who suspect the worst, see
Appendix H.
If you're patting yourself on the back because your printer printed
an italic A, postpone your celebration for a bit. Nearly all BASICs
intercept codes on their way to the printer and alter them in some way.
For example, some popular systems intercept a CHR$(10) (a line feed)
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