Classic Computer Magazine Archive COMPUTE! ISSUE 129 / MAY 1991 / PAGE 72

Faces, fonts, and points. (laser printers)
by William Harrel

Not long ago, the word laser brought to mind sophisticated weaponry, radio transmissions bouncing off the moon, microsurgery, and other futuristic images. Who would've thought that by 1990 literally millions of people would have laser devices sitting on their desks?

Like every other facet of the computer world, printing has evolved substantially. We used to be amazed at the speed of daisywheel printers. They were little more than computer-driven typewriters, but at speeds ranging around 200 words per minute (with no errors), they left human typists in the dust.

Dot-matrix printers seemed wonderful devices-they printed fast and were capable of producing graphics. Later, near-letter-quality (NLQ) printing allowed dot-matrix printers to be used for important business letters. NLQ involved nothing more than teaching the printer to put more ink in a smaller space, or increasing the resolution-the dots per inch (dpi).

Increasing Print quality slowed a dot-matrix printer significantly, however-often to half its draft-mode speed. Printer technology had come a long way, but it was far from perfect. it wasn't until laser printers hit the market that computer hardcopy output reached exceptional quality.

Laser Technology

Laser printers use a technology similar to that of copy machines: The paper is electrically charged as it passes through the device so that a fine black powder called toner will leap from a device known as a printer drum to the paper in the desired patterns. The difference is in the way the image is electronically etched on the printer drum.

Copiers generally feed the image of the page being copied to the printer drum through simple optics. Laser printers use a laser beam to transmit a page in computer memory to the drum.

A big difference between laser printers and other printing devices is that the entire page is programmed, or rasterized, in memory before the paper begins its journey through the printer. Dot-matrix and impact printers, on the other hand, program as they print, printing a little of the page at a time.

The benefits of laser printers are many, one of the most important being speed. In draft mode, a good 24pin dot-matrix will print at somewhere between 300 and 400 characters per second (cps), and considerably slower if it's in NLQ mode. Laser printer speed is measured, instead, by pages per minute (ppm). Many of today's laser printers will churn out eight ppm, and a few will do ten. Soon we'll see these desktop laser printer speeds double. On a basis of 300 words per page averaging five characters per word at eight ppm, a laser printer will approach 200 cps-about the speed of a dot-matrix printer--and all of it letter quality.

Another advantage of laser technology is sound-or, rather, the lack of it. Dot-matrix and impact printers are annoyingly noisy. If you have several printers going at once, conversation is almost impossible, to say nothing of phone calls. All you hear from a laser printer is its fan and, when printing, the low hum of the printer engine as it carries the paper through.

The most significant difference between laser and other printers is the resolution of the output. The higher the resolution, the cleaner the output. Most of today's laser printers print at 300 dpi, though there are several higher-resolution devices on the market, some of them printing as high as 1000 dpi. Most dot-matrix printers produce somewhere around 75 dpi. Laser printers have allowed computer output to move into the realm of typesetting.

Better resolution means better text and graphics-much better text and graphics. Depending on the instructions from the software driving the printer, graphic lines are smooth, gray shading is evenly dispersed, and text (especially in larger fonts) doesn't have that blocky, stairstep appearance associated with computer output.

A Question of Character

It's difficult to talk about laser printers without using some fairly technical typesetting terms like typeface, point size, and so on. Let's pause here a moment for a few definitions.

A typeface, such as Courier, is a family of fonts. Typefaces usually include four fonts: normal, italic, bold, and bold italic. Fonts come in point sizes (abbreviated as pts-there are 72 points per inch) from 2 points on up. Therefore, you would be able to visualize a 12-point italic Courier as being like the output from a standard typewriter, 1/6-inch high, and slightly oblique.

Another pair of terms used in defining fonts are proportional and fixed spacing (or monospacing). Fixed-space fonts-if you are currently using a dot-matrix or impact printer-are probably what you're used to. Courier is a fixed-space font. The individual characters in Courier occupy the same amount of space on a line. An I is given the same amount of space as a G, for example.

Proportional fonts apportion line space to each character according to its width, and pairs of characters are kerned, which means that they're spaced in relationship to each other to give them a more pleasing appearance. For example, a capital T and a lowercase o can be squeezed closer together than their individual widths because the o can be moved slightly underneath the crossbar of the T.

Inside Story

Not only laser printers, but all printers, including typewriters, come with fonts built in. These are called resident fonts. Typewriters and impact printers have wheels or balls you can snap in and out to change type styles. An advantage of laser printers is their ability to accept hundreds of different fonts in all kinds of point sizes.

There are a number of methods to get fonts into a laser printer; the two most common ways are by using soft fonts and cartridges.

Soft fonts are software that is sent to the printer from your computer through a process called downloading, which is a common term for sending data from one device to another. Fonts can be downloaded into a printer's memory as needed for a specific print job (called temporary soft fonts), or they can be downloaded and kept in the printer's memory until the printer is shut off (called permanent soft fonts).

Although there are two different downloading techniques, that doesn't mean that you need two different kinds of fonts. All soft fonts are capable of being either temporary or permanent. The downloading technique is usually determined by the word processor or desktop publishing software.

Cartridge fonts come in cartridges that plug into special slots in the laser printer. Once the cartridge is plugged in and activated, the fonts in the cartridge become resident. There are literally hundreds of different font cartridges available, with a multitude of font combinations. The major drawback to most of them is that, unlike soft fonts, you are usually locked into a limited selection of fonts and point sizes. But cartridges are much easier to install and use than soft fonts.

The Great Language Debate

A laser printer uses a page-description language (PDL) to determine where to put toner on paper. Although there are several PDLs out there, two are at the forefront: Adobe Systems' PostScript and Hewlett-Packard's Printer Control Language (PCL). Which language is better? The best answer is that it depends on your application.

Among other major differences between the two types of printers is price. A PostScript printer can cost thousands more than a PCL printer; however, the prices of both kinds of printers have dropped considerably over the past year, making the decision to go with PostScript less onerous.

PostScript printers are the devices of choice for most high-end desktop publishers. The reasons are many. In several ways, PostScript is a more flexible language than PCL.

PCL printers use a convention for printing fonts called bitmap. Bitmap fonts are produced as patterns of dots that are fixed in position like the elements of a rubber stamp. Every character must have its own bitmap.

PostScript fonts, on the other hand, are drawn based on instructions that reside in memory or are downloaded from your computer. Fonts created from instructions rather than from bitmaps are called outline fonts. Since each character is drawn separately, it's easy to manipulate, stretch, or treat text with any number of other special effects, such as reversing (mirroring), skewing, outlining, and so on. PostScript fonts can be rotated to any degree or printed with different fills. The only limitation is your imagination.

Another font advantage of PostScript is that most devices using this language come with 35 scalable fonts, meaning that all 35 can be sized in increments of 0.5 points, from 2 points to more than 700 points (depending primarily on your software). Any outline soft font downloaded to a PostScript printer can also be scaled accordingly.

Although the latest PCL version (Version V, used in the LaserJet Series III) does contain some limited font scaling and a few other font special effects capabilities, most PCL printers must have a separate font in the printer for each font attribute and point size. In other words, to use Times 10 point in normal, bold, italic, and bold italic, you must download four files to the printer. If you also want to use these four Times fonts in a 12-point size, you must download four more files.

Font files must be stored either on your hard disk or on floppies. They take up an enormous amount of disk space (to store three typefaces in various point sizes ranging from 6 point to 36 point in all four fonts can take ten megabytes or more).

Also, soft fonts require huge amounts of printer memory. This drastically limits the number of fonts and the size of graphics you can use per document page. Another PCL disadvantage is that, depending on the speed of your computer, it can take a long time to download fonts. Larger point sizes can take several minutes.

Even though PCL font cartridges follow the same convention-fonts must be present in specific attributes and point sizes-they can eliminate some of the inconvenience. As mentioned, most cartridges are limited. However, a number of megafont cartridges have recently become available. Computer Peripherals, for example, makes a cartridge called SuperSet + that contains over 400 fonts. And several companies make PostScript emulation cartridges that give certain PCL printers all the font features of PostScript. PostScript printers, in contrast, have no need for cartridges. Their outline fonts use significantly less disk or printer storage.

Another PostScript advantage is greater graphics control. Since PostScript draws its lines and arches (rather than bitmapping them), the smoothness of graphic elements isn't dependent on the quality of the information sent from the computer (as it would be with a bitmapped language like PCL). Instead, it's dependent on the highest resolution of the printer. Any PostScript printer will provide output at the limits of its resolution, whether that is the standard 300 dpi of desktop laser printers or the far higher resolution of typesetting machines. PostScript printers are capable of printing Encapsulated Postscript (EPS) graphics, which can contain intricate patterns and fills unavailable in PCL.

Desktop publishers utilize PostScript laser 300-dpi output to create drafts of documents that require higher resolution typesetting. After all the revisions have been made, the document is then played out on Allied Linotype's Linotronic typesetters at 1270 dpi or higher for excellent quality. All you have to do is take your disk to the local graphics service bureau.

PCL will drive a few typesetting machines, but so far this type of output hasn't caught on. You could be hard-pressed to find a service bureau that can typeset from PCL files.

PostScript is not without its disadvantages. As mentioned, the price of PostScript printers has always been significantly higher than that of PCL printers. Laser printer prices have dropped dramatically over the past year or so. However, while the price of low-end PostScript printers has come down by 40 percent (to around $3,000), the price of the least-expensive PCL printers has dropped by 50 percent (to less than $ 1,000). The gap narrows almost to insignificance, however, with the introduction of a $995 PostScript printer called the JetScript by the Printer Works (3482 Arden Road, Hayward, California 94545; 415-887-6116). One reason for this printer's low cost is that it uses a refurbished printer engine. Watch for a review of this machine in an upcoming issue of COMPUTE.

PostScript is also notoriously slow. Waiting for intricate or bitmapped graphics to print on a PostScript device can be excruciating. However, relatively new technology has sped PostScript by as much as a factor of 5. Most documents will print with little or no delay.

Before You Buy

The question of whether you need PostScript or PCL is not the only consideration in buying a laser printer. Some printers don't use either language, which means you could have trouble using them with some of your software. Canon, for example, makes several printers that use a language called Canon Printer System Language (CaPSL). These printers have nine scalable fonts and can be upgraded to almost the same standards as PostScript. However, at present not all software programs support Canon printers. There are also printers, such as several NEC lasers, that support both PCL and PostScript.

There are many, many laser printer manufacturers and distributors out there today, and you'll find printers with all kinds of configurations and a wide range of prices. Printer RAM, for example, is an important feature. Many printers are shipped with only 512K of RAM, which is barely enough to download a couple of fonts or to print about half of a page of graphics. PostScript printers with two or three megabytes of RAM can store additional data while printing a page, freeing up your computer to start the next page sooner.

Printer RAM can almost always be upgraded, but at a cost somewhat higher than upgrading your computer's RAM.

PCL printers handle memory a little differently from PostScript printers, but a good rule of thumb is that you'll need a 1MB minimum for fullpage graphics and more than 1MB if you want to use many soft fonts and intricate graphics on the same page. Printer RAM of 3MB is almost impossible to overload, unless you're doing high-end desktop publishing.

Laser printers also come with different font configurations. Some, such as the HP LaserJet Series IIP, come with only a few fixed-space fonts, and a few PostScript printers have well over the standard 35 fonts resident. Not all PostScript printers use true Adobe PostScript, which could mean that Adobe Type I (the one used by typesetters) downloadable fonts are not supported.

Paper-handling options are also important. Some printers cannot handle paper sizes smaller than 8 1/2 X 11 inches, and many will not print envelopes. Some have paper trays that hold only 100 sheets of paper, while others have more than one 250-sheet paper tray, and many printers can be equipped with much larger paper trays. Still other printers, such as the HP LaserJet Series IID, support duplex printing-printing on both sides of the paper.

These configuration questions should all be considered before you go shopping for a laser printer. Sometimes one or two hundred dollars can make a world of difference in the printer you finally set on your desk. There are many good laser printers available and some that are not so good. A safe plan would be to purchase a product that can be upgraded later; you never know where your computer application might take you. PostScript Alternatives Buying a PCL printer for under $ 1,000 is for many computer users the only economically feasible means for obtaining a laser printer. Many PCL users find themselves wishing later they had the power of PostScript. Today there are a number of PostScript alternatives for most PCL printers-everything from low-cost software, like GoScript and Freedom of Press, to expensive boards and other not-so-expensive hardware.

Probably the most convenient and practical solution is a PostScript emulation cartridge. PostScript cartridges work the same as font cartridges: Just plug them in and tell your software to use PostScript. These cartridges endow PCL printers with all 35 scalable fonts and all other Post-Script functions at a fraction of the cost. There are several available, and they range from $300 to $700. Vendors include Computer Peripherals, Adobe Systems, Pacific Data, and Hewlett-Packard.

The main thing to remember when buying a PostScript cartridge is that they all require more than the 512K of RAM that comes standard with some PCL printers. Currently, most require a minimum of 2.5MB of RAM, but Computer Peripheral's JetPage requires a mere 1.5MB.