Computer printers
Since the first printers were connected to a computer, there have been two industry standards for plain text: ASCII and EBCDIC. There wasn’t much to configure, just the top of page (pin-fed greenbar paper), lines per inch and page length. The text was printed by either a rotating drum with all the characters in each of 80, 120 or 132 column positions, and hammers that would hit the ink ribbon at just the right moment for each letter across the paper. Enter the era of dot matrix, corebar and laser printing…now printers can have large and small fonts, even rotated characters and graphics. But in the beginning, the conversion of text and optional page layout information was processed by the internal electronics, the formatter. This formatter would start with a blank (white) set of dots representing every dot on the page. Then using font descriptions ((typically in the printer ROMs), the dots needed to create the letter “A” would be set in this large arrays of dots. When the page is completed, the print engine is then fed each horizontal row of dots and the laser, mechanical pin or ink squirter places the dots on the paper.
Two major page layout standards emerged, HP’s PCL (Printer Control Language) and Postscript. PCL was particularly use in that it is based on plain ASCII but with extensions called escape sequences. It is also the most common printer language in use today. If you send “ABC” to a PCL printer, ABC will appear in the paper. (Note exceptions further down in this document) Postscript differs in that a lot of special codes are required to print even the simple ABC text.
Host-based printers
Host-based are printers that cannot be used in a general environment such as Unix or mainframes. The reason is that a critical component in the printer, the formatter, has been moved to the driver in the host system. Essentially, these printers are simple dot squirters where the computer must supply all the dot information ready to print. This means that text, fonts, graphics, colors, etc must all be formed in memory (rasterized) in the host and then formatted to match the printer’s print heads. Because each printer model has hardware-specific requirements, a complex and custom driver is required. If HP does not supply a driver, the printer cannot be used for even the simplest printing task. These printers are also called PPA or GDI printers.
What is a PPA printer?
Deskjet 710c, 712c, 720c, 722c, 820cxi, 820cse, 1000c, 1000cxi,
3300c, 3400c, 3500, 3600
Photosmart Photo printers (C3804)
Laserjet 3100 series, 1000 series
All-In-One printers (fax, scan, copy, print)
…many others have and will follow…
Some HP printers use a printing system called Printing Performance Architecture (PPA). PPA printers have limited electronics and firmware that are different from earlier HP inkjet models in the past. No formatting is performed in the printer. All formatting, such as color matching and correction, half-toning, edge enhancement, tone correction, and ink management, is handled by software in the host computer (ie, host based). PPA printers cannot be used with JetDirect LAN cards or boxes. So unless HP provides a driver for a specific OS, they cannot be used even simple text printing. Here is a (very old but relevant) link about PPA printers:
http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=bpd02937
There is a distant cousin of the PPA printer called JetReady. All the restrictions apply equally to both PPA and JetReady printers, that is, the same problem with no ASCII compatibility.
What are GDI printers?
PPA is not the same as GDI (Graphics Display Interface) which is defined by Microsoft:
http://msdn2.microsoft.com/en-us/library/aa286572.aspx
These are printers with special firmware and electronics to accept the MicroSoft-GDI codes and form an image in printer memory. GDI is proprietary to MS-Windows so finding compatible systems is highly unlikely outside the Windows environment. These printers rely on the computer’s processor to rasterize the print job. Most host-based printers use the GDI interface built into Windows (hence the “GDI printer” term), so there is no need to convert the data to PostScript, PCL, or other printer language.AS you might expect, GDI is only featured on Microsoft platforms.
All-in-One printers
There are a wide variety of AiO printers which are really scanners, faxes, copiers as well as a printer. There does not seem to be a consistent way to identify Windows-only AiO printers, but in general, a PCL compatible printer implies plain ASCII printing. Many older AiO printers cannot be used with a LAN card at all. Unfortunately, PCL-compatible means PCL 5 and lower (PCL4,3,2,1) while PCL-5e is somewhat ambiguous. A PCL-5e printer may or may not be able to print plain ASCII from OS platforms such as HP-UX, Solaris, AIX or mainframes.
OfficeJets, etc
Many OfficeJet printers are not designed for networking at all so adding a JetDirect External box will not work either. The original PhotoSmart printer is not compatible with a JetDirect interface. Most are host-based printers.
LaserJets
Until the introduction of the LaserJet 1000 series and 3100 series, all LaserJets would work with either a plugin JetDirect LAN card or an external box. So now picking a LaserJet printer for Unix requires careful attention to the specs. Avoid any printer that says:
host-based
Windows or Windows-only
GDI
Sleek
PPA
Here is a link about compatible HP printers:
Always look for the words PCL and avoid PCL5e and higher levels when choosing a printer for HP-UX and other Unix flavors. Although it says PCL, PCL-5e and PCL-6 does not mean ASCII-compatible, a departure from a 25-year old standard.
LINUX note:
LINUX has a number of volunteers that write open source code for printing and CUPS (Common Unix Printing System) is the best known of the printing systems. Many HP and non-HP printers have been ported to CUPS, including host-based versions. This is another possible solution to getting inexpensive printers to work on Unix systems. Here are two links that talk about CUPS:
http://en.wikipedia.org/wiki/CUPS
http:///service-it-direct.s7.devpreviewr.com.cups.org/
– See more at: http://serviceitdirect.com/blog/host-based-printers-and-hp-ux#sthash.IEXmKss3.dpuf
Tags: HP-UX