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EN What are Printer Commands? 1-3
What are Printer Commands?
PCL printer commands provide access to printer features. There are
four general types of HP printer language commands:
z control codes
z PCL commands
z HP-GL/2 commands
z PJL commands
Control Codes
A control code is a character that initiates a printer function, for
example Carriage Return (CR), Line Feed (LF), Form Feed (FF), etc.
PCL Commands
PCL commands provide access to the printer’s PCL control structure.
The PCL structure controls all of the printer’s features except those
used for vector graphics, which are controlled by the HP-GL/2
commands.
PCL printer commands consist of two or more characters. The first
character is always the ASCII escape character, identified by the ?
symbol. ? is a special control code which identifies the subsequent
string of characters as a printer command. As the printer monitors
incoming data from a computer, it “looks” for this character. When this
character appears, the printer reads it and its associated characters
as a command to perform and not as data to print.
Note PCL printer commands (other than single-character control codes)
are also referred to as escape sequences. The terms printer
command and escape sequence are used interchangeably
throughout this manual.
Once a PCL command sets a parameter, that parameter remains set
until that PCL command is repeated with a new value, or the printer is
reset to its user default environment. For example, if you send the
printer a command to set line spacing to 3 lines/inch, each page
prints 3 lines/inch until the printer receives a different Line Spacing
command, or the printer is reset.