Do you like printing stuff? Or doing things for other people who like to print stuff? Then this tip might be just what you need, especially if you like doing complex things with your prints.
I'm just going to say this up front and be done with it. I don't like printers. Never have, never will. I think it dates back to the days when we had the big line printers and I was never able to get the paper lined up to suit Gloria, the night operator. It shouldn't have mattered, but I was younger then and she was hot. I have my pride. It just always seemed to me that printers were the perfect demonic combination of electronics and mechanical gears. But that's my problem, not yours.
Printer Connection Options
Perhaps things would work out better with printers if they just sort of magically worked. You could just think that you want something to print, and look at the printer you want it printed on, and voila!
Unfortunately, printers need to be attached to the system you want to print from. There are a number of ways that this can be done—via a TCP/IP connection, a direct connection using a PC, or a variety of workstation controllers (Twinax, ASCII, LAN-attached printers, etc.).
If you're using a TCP/IP connection—and that's quite common—then you need to use one of a number of network print protocols to control the process. One example is Intelligent Printer Data Stream (IPDS), which provides excellent print performance and allows you to use Advanced Function Presentation (AFP) capabilities. Another is Simple Network Management Protocol (SNMP), which uses two TCP/IP ports (one to send print data and a second to track job status). But the hero of this story is Printer Job Language (PJL), which does the job while using just a single TCP/IP port and bi-directional communication.
What Is PJL?
Interestingly enough, PJL was actually developed by Hewlett Packard, and it's a standard communication language for many printers. Along with Printer Control Language (PCL) or Postscript (PS), it helps control how the print jobs are handled. Specifically, PCL/PS handles the layout part of the print while PJL allows you to pick up feedback from the printer and to do a variety of advanced functions—one of the most important being the ability to dynamically switch languages on a job by job basis. I am not talking about Spanish to German here, but rather switching from a PCL to a PS control language for the print.
How do you do this (use PJL in general and switch languages in particular)? I thought you would never ask. And actually, I was hoping you wouldn't.
Creating a PJL Script
The first thing you have to do is build a PJL script. This is done in a text editor.
As you do this, a number of commands must be entered, and the order in which you enter these is important.
Universal Exit Language (UEL) Command
The UEL command is executed first. It tells the printer to finish up the job it's doing (finish it normally, that is) and then to be ready to accept input from the active printer control language, which would be PJL. This is the first command that must be executed in a PJL script. And it must also be the last command issued in a PJL script.
JPL Comment Command
The next command is optional, but it would be on the same line if it occurred. This is the command that allows you to put in a comment to identify what this particular script is going to do. It follows the basic format of a PJL command. (The UEL just gets you into the PJL language; it's not really part of it.)
It starts with the control keyword @PJL, followed by the command COMMENT, followed by whatever comment you want to put in, followed by the line carriage return and line-feed characters required by the language.
@PJL COMMENT 'whatever comment you want' <CR><LF>
@PJL COMMENT Switch to PS language <CR><LF>
Language Switching Command
Since this tip was designed to deal specifically with switching from one control language to another (that is, from PCL to PS or vice versa), you need to use one of the two following multi-line commands.
@PJL ENTER LANGUAGE = PCL<CR><LF>
<ESC> . . . . PCL Job . . . . <ESC>E<ESC>%-12345X
@PGL ENTER LANGUAGE = PostScript <CR><LF>
%!PS-ADOBE … PostScript Print Job … ^D<ESC>%-12345X
@PGL ENTER LANGUAGE = ESCP <CR><LF>
… ESC/P Print Job … <ESC>%-12345X
There are many other commands you can issue using PJL, including indicating what page to start with and how many pages to print, getting the status on a print job, and many more. For a full description of what's available in PJL, you should probably take a gander at the PCL/PJL Printer Job Language Technical Reference Manual from HP.
One More Thing
It won't take you long to write the PJL job script. The question then is, what do you do with it? And that's another story but one that we will postpone until the next exciting installment of TechTips: The Fascinating World of PJL. I know, I can't wait either.