Escape Sequences; Printer Commands - Epson LQ-2550 User Manual

Escape sequences

Although there are more than 30 control codes available to control the
operation of your printer, many more codes are required to run today's
sophisticated printers. Therefore, ASCII codes are grouped in sequences
to represent certain functions. These code sequences use the ASCII codes
with decimal values of 32 through 255, normally reserved for characters
and punctuation, to control printer functions. This is done by first
sending a standard code to tell the printer that the codes that follow are
to be used as control codes, not as characters or punctuation.
The standard code that is sent at the beginning of one of these code
sequences is the Escape code, decimal value 27. Any sequence of codes
starting with the Escape code is called an Escape sequence. You will
probably see Escape written in different ways-such as ESC, Esc, and
when used within a command.

Printer commands

In order for the printer to recognize the instructions it receives, ASCII
codes must be sent in a specific format, called a command. An Escape
sequence is a command, as is any ASCII code or sequence of codes that
instructs the printer to carry out a particular function. Your software
continually sends commands to your printer and your computer screen.
These commands instruct the printer to perform such actions as print in
a particular typeface, feed the paper a certain amount after printing each
line, and start printing on a particular spot on the page.
Some software programs let you send these commands yourself. This is a
powerful feature because it allows you to enhance your text in ways that
may not normally be available through the software. For example, many
word processing programs do not offer italics. By inserting a command
in your document, however, you can use italics anywhere you like. The
commands that your printer recognizes are listed in the Command
Summary in Chapter 8 and on the Quick Reference card at the back of
this manual.
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Using Software and Graphics