HP PCL/PJL reference (PCL 5 Printer Language) - Technical Reference Manual Part I

EN Syntax of Escape Sequences 1-5
Syntax of Escape Sequences
There are two forms of PCL escape sequences: two-character
escape sequences and parameterized escape sequences.
Two-Character Escape Sequences
Two-character escape sequences have the following form:
? X
where “X” is a character that defines the operation to be performed.
“X” may be any character from the ASCII table within the range
48-126 decimal (“0” through “~” - see Appendix A). For a list of the
two-character escape sequences supported by the printer, refer to the
“PCL Feature Support Matrix” in Chapter 1 of the PCL 5 Comparison
Guide.
Following are examples of two-character escape sequences:
? E a two-character escape sequence used for
resetting the printer.
? 9 a two-character escape sequence used for
resetting the left and right margins to the printer’s
default settings.