PCL and PostScript

September 1996

It appears to be an axiom of WindowsLand that you can never have too many fonts.

It used to be that fonts were very dear. My first experience with word processing was with an IBM 8100 system, which used a mechanical printer that contained removable font wheels. The word processing program on this system did allow you to change fonts, but when you printed your document you got a message to change the font wheel everytime the font changed in the document. If a page had three different fonts changes, you got three different messages. This would not really have been so bad, except that this system was so expensive (it was from IBM, after all) that eight workstations shared a central printer, and you never knew just when your document was going to print, and you had to run down the hall to change the wheel, and it was completely useless. So I learned to love Courier 10.

When I started using WordPerfect for Dos, version 5.0, you got a couple of fonts tossed in with the package, and you could go to a company named Bitstream to get more for about a hunnert bucks a face. And you had to go through this huge installation process, because the Bitstream fonts were not scalable, and you had to generate a library of each size of each face you might want to use.

About that time, another company named Swifte started marketing fonts for about $25/face, but packaged in groups of four. So you still paid a C note, but at least these were scalable on the fly. Within your word processor, you could select both a face, and a size, and that was pretty fantastic for those days so long ago. (We are talking about 1989 here, folks.) Swifte seems to be still around, and is currently selling something called Typecase, which is their whole bag of a couple of hundred fonts, for about fifty dollars.

All these packages presume that you have an HP LaserJet or compatible printer. The LaserJet contains memory and a microprocessor internally that understands a language HP developed called Printer Control Language, or PCL. The early versions of this language were really quite simple. This language allows you to place a dot, or a filled rectangle (of any level of gray), or an internal font (the LaserJet II had only two such fonts, Courier and LinePrinter) anywhere on the page of a standard sheet of paper. If you wanted a font not known to the printer, you could download font faces, but they have to be made up of dots or rectangles. It is really quite amazing what can be done with this, because most font packages that you buy to this day still run on a LaserJet II, even though the later LaserJet models increased the functionality of the PCL language. It is now up to Rev 6, I believe.

There is another solution, and that is Postscript. This is something invented by the Adobe people (ok, probably the Xerox Parc people, but Adobe marketed it). It requires both special software in your computer, and special hardware or software in your printer. The Postscript engine in the printer is much more sophisticated than PCL. In essence, It understands mathematical functions. Thus, a font face can be built entirely from a set of functions, and the printer internally can then scale the size of the font, or rotate the font, or stretch it, or do anything to it that applying some transformation formula to the type face function will allow to happen. Things get even better for graphics programs, because after all, a drawing is essentially just a series of a mathematical functions. Adobe sold their translator software to the printer companies, and gave away the Postscript compiler to the application software vendors. There are many books available on how to directly access the Postscript engine of your printer. Most people do not need to know this level of detail, however.

We, the happy users, see this software built into drawing packages like Corel and Micrographics and the other vector drawing packages. (Postscript is not much help with bitmap drawings, because after all, bitmaps are just bunches of dots.). For some reason, the Mac side of the world immediately jumped onto this technology, and Mac printers all understand Postscript as their native language. Perhaps this came from the already graphical bent of the typical Mac user. The downside was that Adobe charged a huge royalty for the use of this engine, like several hundred dollars per printer, and this made Postscript printers much more expensive. But that was OK with Mac people, since all the other Mac hardware was real expensive already.

The Dos and Windows people, being more budget minded, drilled down on the LaserJet's PCL features, for which no royalty was charged. This all worked adequately for text, and Windows people did not originally get into graphics as heavily as Mac people, or if they did they used bitmap drawing packages like Paintbrush, so the LaserJet PCL was OK for that too.

Now of course, the latest LaserJets have Postscript either as an option, or built in. For a while, with the LaserJet III, you had to insert a cartridge when you printed a Postscript document, and take it out when you did not. If you got it wrong, you got dozens of pages of gibberish. This works not at all well for a central shared printer, as we have in our office. The other gotcha was that if you pulled the cartridge when the printer power was on, you fried the cartridge and maybe the printer too.

I was first introduced to all this by James Dodds, proprietor of AllWrite Publications, who does much of the contract technical writing for us at World Wide Widgets. He had become quite used to Postscript functionality and quality in his former years of toiling away in the apple vineyards, and his delicate sensibilities were quite upset when he came to work for us and was handed a PC. Those sensibilities were rubbed raw the first time he sent a graphic to our LaserJet printer. He was very insistent that we immediately get the $400 Postscript cartridge for our LaserJet. Because WWW is widely known for its Contractor Oriented Attitude, we caved in and got the cartridge. As soon as it arrived, he displayed the same drawing file, printed on the same printer, but one with PCL and one with Postscript engines, and the differences jumped right out at you. The quality of the Postscript drawings are quite superior. And this goes for text and fonts also. Although Mr Dodds loves to hand you a magnifying glass so you can see each and every jaggie in the PCL font, and how sleek and smooth the Postscript fonts are, even those of us that do not fully understand why a point is not quite 1/72 of an inch can see the difference between the two engines with the unaided eye.

When you start looking at font catalogs, it appears that TrueType fonts predominate. TrueType fonts appeared when Windows 3.1 appeared, and was BillG's one finger salute to Postscript. TrueType has the advantage that TrueType fonts not only work on PCL printers, but on your VGA screen as well, whereas Postscript got all wound up in something called Display Postscript which has never caught on. So today, even if I am going to generate a Postscript document, I will view it on my screen in TrueType as an approximation. Some font manufacturers will send you a TrueType font for your screen that matches the Postscript font for your printer.

However, Postscript can guarantee that what you print on your 300 dpi LaserJet, or your 96dpi Epson, will be true to form, if not resolution, to a 2650 dpi professional Linotronic printer. It appears that TrueType cannot make that claim, and it is certainly true that the older fonts that directly worked with PCL cannot either. Postscript would seem to be the choice for somebody who is generating a document at work on a relatively cheap printer that will later be redone on professional equipment.