Computer-Printer Communication - Epson LQ-2550 User Manual

When buying graphics software, always make sure the program has an
option to print on an LQ printer. Any program with an option for an LQ
printer should give excellent results, using different dot densities to
produce a realistic scale of grays.
If you plan to use color, be sure that the program supports color for an
LQ printer.
Most graphics programs have a printer selection procedure, in which
case you should check the lists on page 4-2 to find the proper selection.

Computer-Printer Communication

Your computer communicates with your printer using a standardized set
of numbered codes called ASCII codes (American Standard Code for
Information Interchange). When you press the letter A on the keyboard,
it is translated into the ASCII code for A, transmitted to a peripheral
device such as your computer screen or your printer, and then converted
back into the letter A.
There are ASCII codes for all the letters in the alphabet, both uppercase
and lowercase letters, and for the numbers 0 through 9. The ASCII set of
codes also includes most punctuation marks and some codes that control
printer functions.
In the Command Summary in Chapter 8, each code is expressed three
different ways: as an ASCII character, as a decimal number, and as a
hexadecimal (base 16) number. For example, the uppercase letter A is
represented as the ASCII character A, the decimal number 65, and the
hexadecimal number 41. The numbering system you use depends on
your software and your preferences.
All letters, numbers, and punctuation marks are assigned decimal
numbers from 32 through 255. ASCII codes with decimal values of less
than 32 are called control codes, because they control the operation of
your printer and other peripherals. These ASCII characters do not
usually have corresponding keys on the keyboard and cannot be printed
as characters by your printer.
Using Software and Graphics 4-5