Basic Communications - Epson FX-80 User Manual

Table 2·1. LiSTing on Several Computers.
Command Computer
LLIST
TRS-80 and Microsoft BASIC
LIST"COM!il:"
HX-20
PR#l
Apple
LIST
PR#!il
If your listing is more than a page long (or if you didn't start the
listing at the top of a page), you may notice that it is printed right over
the perforation. Don't worry, we'll show you how to correct that in
Chapter 8, when we cover forms control.
Meanwhile, printing a program LISTing is a fundamental function
of the printer. Be sure you manage this before continuing (if you have
trouble, consult your computer's manual for help).
BASIC Communications or ... The Nonexistent
Standard
Part of the difficulty in controlling communications between com-
puter and printer is the lack of a standard coding scheme. When your
computer sends out a numeric code for the letter A, the printer had
better interpret that code as an A or we're all in trouble. For frequently
used characters like the alphabet, numerals, and keyboard symbols,
most manufacturers use the American Standard Code for Information
Interchange (ASCII, pronounced ask-key and shown in full in Appen-
dix A). Use of this coding system assures that computers and printers
use the same set of numbers to represent the most commonly used
characters. Unfortunately, the original ASCII standard does not allow
for the advanced features in today's printers and computers_ Manu-
facturers have therefore adjusted the code to suit their individual
needs.
This means that we are faced with compatibility problems between
printers and computers. These inconsistencies can usually be over-
come by sending the special codes required by the printer in the form
of numbers. In the BASIC language, the codes are sent via the CHR$
function.
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