Epson FX-100 User Manual download pdf (Page 58)

instead of an Italic A, pay close attention to the next three paragraphs.

The original ASCII code was designed to use the decimal numbers

zero 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 BASIC printer

drivers that intercept any number in the upper half of the range

(128 -

255)

and automatically convert it to the lower half of the range by

subtracting

128.

In these systems such a code as CHR$(193) never makes it to the

printer. The printer driver subtracts

128,

which means that the code

for Italic A gets to the printer as a CHR$(65). The printer then

produces a Roman A.

For many applications, you won’t need the upper half of the ASCII

codes. For others, the inability to generate codes greater than 127 will

be an obstacle. Whenever we can, we suggest ways to get around this

obstacle. In Chapter 5, for instance, we discuss Italic Mode, which is

the FX designers’ method of making Italic characters easily accessible

to all users.

If you’re patting yourself on the back because your printer printed

an Italic A, postpone your celebration for a bit. Nearly all computers’

BASIC programs intercept codes on their way to the printer and alter

some of them. For example, some popular systems intercept a

CHR$(l0)-line feed-and send out a CHR§(13)-carriage return-

instead. Typical problem codes involve the numbers 0 and 9 to 13.

Your computer manual may alert you to these problems, Or experi-

ence may have to be your guide.

In order to help computer systems that can’t send a zero in a CHR$

command, several printers’ instruction sequences allow such options

as using “0” (quote-zero-quote) in place of CHR$(0). Besides mention-

ing some of these solutions within the text of this User’s Manual, we

have written a troubleshooting appendix, Appendix F.

Control codes

Enough talking about problems. Here’s a program line to try:

10 LPRINT CHR$(7)

Be sure to use the appropriate printer access commands for your

system.

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