HP PCL/PJL reference - Printer Job Language Technical Reference Manual

EN PJL File System Commands 9-17
The Alphanumeric ID command needs to know the number of bytes
being sent after the terminating W. In this example, we are sending 8
bytes. The first byte, which is the ♣ symbol, is the control-byte (The ♣
symbol is the character with a decimal value of 005). This control byte
indicates that the Alphanumeric ID command will be used to
associate the current macro ID to the string ID. The other 7 bytes are
the characters that make up the string ID (a_macro).
Eighth Command
<ESC>&f4X
The Macro Control command with a value of 4 enables automatic
overlay for the macro with the last specified ID. That is, this command
prints the macro.
Note that <ESC>&f2X and <ESC>&f3X will also work here.
Ninth Command
<ESC>E
The Printer Reset command causes the printer to print and eject the
page. It also restores the User Default Environment and deletes
temporary fonts and macros.
Tenth Command
<ESC>%-12345X
This PJL command causes the printer to exit the active printer
language and return control to PJL.
Eleventh Command
~@PJL DEFAULT DISKLOCK = ON <CR><LF>
This command sets the disk or flash memory to read-only. In this
state, it is not possible to format the disk, download fonts or macros,
or delete fonts or macros.