Chapter 2: Send It A Message - Epson MX-80 User Manual

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- Send It A Message
Chapter 2
Send It A Message
The MX-80 Printer is smart. It knows how to follow instructions.
Any Code Devised By Man Can Be Broken By Man
Many instructions are sent to the Printer. Every letter, number, and other charac-
ter travels from the computer through the printer cable in the form of a code
made up of numbers. We know it as the ASCII code (American Standard Code
for Information Interchange), pronounced ASK-Key.
Let's take a quick glance at Appendix A to refresh our memory. The decimal
number 65 stands for the letter A — etc.
The ASCII code numbers for upper case letters, numbers and punctuation are
pretty well standardized around the world. Unfortunately, the remaining code
numbers are not very well standardized, even among computer manufacturers
within a single country.
We can also send "special" codes to make the Printer print narrow letters, wide
letters, actual graphic characters from the screen, plus do many other things. To
take advantage of all these features, however, the computer has to be able to send
these codes.
1
. 1
J
1
As we will see, each with his own computer, not all computers can send all codes.
With printer technology advancing faster than computer technology, the
computer is replacing the Printer as the weak link in the system.
The Code Courier
In many cases, the easiest way to send these special codes for special things is to
"build" them into the computer program along with its "regular" codes for letters
and numbers. We can do this quite easily using programs written in the BASIC
language.
We can also send these special codes at the BASIC "command level" before
running a program. A program can also contain codes to change earlier codes,
allowing us to print things the way we want them, when we want them.
The route to success in all cases is via CHRS.
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