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Inventing Postscript, the Tech That Took the Ache out of Printing


Repeatedly, in his earliest makes an attempt at controlling laser printers, John Warnock received the message, “Web page Too Advanced,” from a recalcitrant machine. Any system he designed, he vowed, must have a “Print Something” structure. That purpose led in the end to a web page description language known as PostScript, immediately the de facto normal of desktop publishing.

This text was first printed as “‘PostScript’ prints something: a case historical past.” It appeared within the Might 1988 concern of IEEE Spectrum. A PDF model is obtainable on IEEE Xplore. The diagrams and images appeared within the authentic print model.

Again then, Warnock already had a tough thought tips on how to “Print Something.” However later he bumped into a unique impediment, when his employer, Xerox Corp., proved loath to help a really normal language. So off he went, with Charles Geschke and a number of other different colleagues, to discovered Adobe Programs Inc. in Mountain View, Calif. By that point, PostScript was solely two main items of analysis away, though one—the event of kind font algorithms—was “a analysis venture that needed to succeed,” says Warnock, and the opposite had been described as one of many world’s most tough issues.

The remainder is desktop publishing historical past. PostScript can actually do something, although extraordinarily complicated photos can take as a lot as an hour of computation time. It first appeared within the Apple LaserWriter, which was launched in January of 1985. Right now it has been adopted by 23 producers of laser printers, with extra nonetheless signing on.

This story is as a lot about luck and guts as about issues of precept and sensible software program engineering.

Nonetheless, this story is as a lot about luck and guts as about issues of precept and sensible software program engineering. It will have been fairly totally different had Warnock and firm not been in the proper place on the proper time to fulfill the proper particular person.

The time was proper due to the imminence of three {hardware} developments: the primary low-cost, bit-mapped private pc, the primary low-cost laser printer, and a decline in worth of high-density reminiscence chips. And the proper particular person was Apple founder Steven Jobs, who invented the primary, hoped for the second, and advised Adobe to powerful out the third.

Right now laser printers are quickly changing the daisy-wheel printers within the workplace, pushing out letter-quality kind as their laser obeys the instructions of straightforward software program. However given extra subtle software program like PostScript, laser printers can do way more. They’ll print many alternative kind fonts and make the letters dance across the web page hand in hand with drawings and images. PostScript does all this means—attracts traces and curves, tilts textual content at arbitrary angles, or shades {a photograph} in numerous tones of grey. It’s as full and versatile a programming language as Pascal or C or Forth, having variables, loops, conditionals, operators, and routines and providing any variety of methods to get the identical output.

The PostScript program is created on the pc both by somebody utilizing the language or by desktop publishing software program or different functions software program that interprets, say, the actions of a mouse right into a PostScript program. (Different web page description languages are optimized for one in every of these functions, not each.) That program is shipped over a local-area community or by an RS-232 port to the laser printer. There it’s transformed into directions for the printer by the PostScript interpreter, software program resident in ROM. On the identical circuit board as as much as 2 megabytes of ROM is a Motorola 68000 sequence processor, which executes the directions and causes the pages to be printed.

Issues had been extra elementary with the primary laser printers, which had been in common use on the Xerox Palo Alto Analysis Heart (PARC) within the mid-Seventies. They had been managed by a printing protocol known as Press, which was not a programming language however a set of directions that despatched picture information to a printer in a gradual stream. It dealt with letters and easy photos properly, however for something extra detailed, received the printer to return the message: “Web page Too Advanced.” Thereupon the everyday PARC engineer would simplify the picture.

However when Warnock, a pc scientist with a Ph.D. from the College of Utah, joined the middle in 1978, he instantly started work on a brand new printer protocol. Six years of expertise at Evans & Sutherland in Mountain View, Calif., had taught him the place to start out.

Two men with beards and mustaches seated near a creek bed with concrete sides

Adobe Programs founders John Warnock (proper) and Charles Geschke visited Adobe Creek, inspiration for his or her firm’s title. A dry winter has slowed the creek to a trickle, however the firm has had something however a dry yr. The entrepreneurs in 1982 discovered Adobe an appropriate title for the reason that creek meandered close to each their domes and, much more necessary, had not one of the Qs, Xs, Ys, and Zs then standard with high-tech startups.

The PostScript program is created on the pc both by somebody utilizing the language or by desktop publishing software program or different functions software program that interprets, say, the actions of a mouse right into a PostScript program. (Different web page description languages are optimized for one in every of these functions, not each.) That program is shipped over a local-area community or by an RS-232 port to the laser printer. There it’s transformed into directions for the printer by the PostScript interpreter, software program resident in ROM. On the identical circuit board as as much as 2 megabytes of ROM is a Motorola 68000 sequence processor, which executes the directions and causes the pages to be printed.

Issues had been extra elementary with the primary laser printers, which had been in common use on the Xerox Palo Alto Analysis Heart (PARC) within the mid-Seventies. They had been managed by a printing protocol known as Press, which was not a programming language however a set of directions that despatched picture information to a printer in a gradual stream. It dealt with letters and easy photos properly, however for something extra detailed, received the printer to return the message: “Web page Too Advanced.” Thereupon the everyday PARC engineer would simplify the picture.

However when Warnock, a pc scientist with a Ph.D. from the College of Utah, joined the middle in 1978, he instantly started work on a brand new printer protocol. Six years of expertise at Evans & Sutherland in Mountain View, Calif., had taught him the place to start out.

Simulating New York Harbor

In 1971, Evans & Sutherland had undertaken to equip the New York Maritime Academy with a simulator for coaching harbor pilots. The trainees had been to sit down on the mockup of a ship’s bridge, surrounded by 5 12-foot-high, 30-ft-long (3.6-by-9 meter) screens displaying a computer-generated illustration of New York Harbor, full with buildings, piers, movable buoys, altering climate circumstances, and different ships to be prevented. The system needed to produce photos in full coloration for 5 projectors at 30 frames a second.

Evans & Sutherland had by no means produced something as complicated. It let time slip by till, with solely one of many contract’s three years left, “all people hit the panic button,” Warnock says. So to save lots of time, the corporate had the {hardware} and software program developed in parallel, the primary in Utah and the second by a group led by Warnock in California.

The frenzy planted the primary two seeds for what was to change into PostScript. Clearly, a database itemizing every part within the harbor was each important and must be in-built complete ignorance as to the {hardware} it will finally run on. So Warnock’s group determined to invent a language unrelated to any pc. Solely when the simulator {hardware} was prepared would they construct a compiler to translate the database into the suitable machine language.

In the meantime, feeding details about the harbor into the database proved arduous. Placing maps on a digitizing pill and touching them with a stylus at quite a few factors was not so unhealthy; however utilizing a keyboard to enter the small print—whether or not the purpose touched was a pier of a sure kind or a constructing or an island—was sluggish going. To make this activity simpler, John Gaffney, one in every of Warnock’s group, spent a weekend writing a software program routine that might generate the details about the objects from menus.

By the point the harbor simulator was accomplished, solely barely delayed, Warnock had found how highly effective an object-oriented language is. Not like Primary or Fortran, say, which require the consumer to spell out each final instruction, it packs all these particulars into modules, or objects, which the consumer controls with only a few directives. Warnock had additionally found that making software program device-independent “offers you a substantial amount of leverage and adaptability.”

These classes realized, his group turned to increasing Gaffney’s little interpreter right into a full programming system for computer-aided design (CAD). In 1977, that venture was launched by Evans & Sutherland as The Design System. “It had an interactive, stack-oriented structure,” Gaffney stated, “with easy instructions for pushing and popping arguments onto and from the stack and a wealthy dictionary for look-ups.” (Such an structure shops information as it’s obtained, stacking it like a pile of books. A command like “add” would “pop” the topmost items of knowledge from the stack, act on them, and “push” the consequence again on the pile.)

Just one copy of The Design System was ever launched, as a take a look at mattress for the ultimate growth, however the different firm’s venture director died and The Design System died with him. Warnock, nevertheless, took the stack and dictionary concepts—together with what he had realized from the harbor venture—to PARC.

A “Jam” session

PARC was then utilizing a programming language known as Mesa. In 1978, quickly after arriving on the heart, Warnock persuaded one other Xerox researcher, Martin Newell, to assist him re-create The Design System in Mesa. The consequence, known as Jam, for John and Martin, proved the ideas he introduced from Evans & Sutherland had been acceptable for laser printing.

Jam was object oriented and gadget impartial, just like the harbor simulator, and in some methods less complicated than The Design System, as a result of printing requires solely two dimensions, versus CAD’s three. Nevertheless it wanted a couple of options, equivalent to kind fonts, present in neither of its ancestors. Furthermore, Warnock remembers, “Xerox was utilizing a unique printing scheme on each printer. The Star workstations [then being developed] had been crumbling below the load of attempting to drive all of them otherwise.”

So Warnock and a gaggle of researchers headed by Charles Geschke got down to merge Jam with the older Press protocol into Interpress, an ordinary, device-independent language able to driving all Xerox Corp.’s laser printers. Interpress was accomplished in 1981, however unhappily, the tip was not in sight. Due to the compromise between Jam and Press, “the language turned difficult in its redesign,” Warnock says. And Xerox begged the problem of standardization by producing a number of variations of the language, so the corporate’s older laser printers might run some type of it.

Worst of all, to Warnock, was the insistence that printers all the time run at their rated speeds. Since a 20-page-per-minute printer couldn’t produce something very complicated in three seconds, he was again dealing with his “Web page Too Advanced” nemesis. The constraint derived from the copier enterprise, Geschke explains, the place “pricing of leased machines was primarily based on copies per day. However in digital printing, in our opinion, perform was most necessary, so there was an actual variance between our and the Xerox place.”

All the identical, within the perception that any normal was higher than none, Warnock and Geschke started selling Interpress inside Xerox Corp. Finally, they received—type of. However Xerox added, Warnock remembers, “’We’re going to maintain it a secret as a result of it’s so fantastic and if we publish it the Japanese would possibly implement it earlier than we do.’ “Gee,’ I stated, ‘A secret normal—I discover this a tough idea to grasp.’”

Satisfied that Xerox was making a mistake, Warnock and Geschke left PARC to implement their web page description language as soon as once more, however this time inside a company they managed. With the assistance of David Evans of Evans & Sutherland and William Hambrecht of Hambrecht and Quist, a San Francisco-based enterprise capital agency, they wrote a marketing strategy and integrated in December of 1982.

They supposed each to promote this setup as a turnkey system and to franchise the publishing equal of a one-hour picture retailer.

Desktop publishing, although, was not what Warnock and Geschke at first had in thoughts. The system they foresaw consisted of a workstation linked by a device-independent, page-description language like Jam to a laser printer for draft printing, a photo-typesetter for the ultimate output, and no matter different output gadget they may later add. No different publishing package deal then obtainable used the identical software program for various output units. And so they supposed each to promote this setup as a turnkey system and to franchise the publishing equal of a one-hour picture retailer.

Adobe then consisted of Warnock, Geschke, and a core of different engineers employed from PARC: Daniel Putman, Thomas Boynton, and Douglas Brotz. As they deliberate to purchase no matter {hardware} they wanted after they’d perfected their programming language, they targeted first on Jam. They labored in C, on a VAX 750 working Berkeley Unix, to develop the language, they usually examined in on a Solar workstation driving a full-size laser printer that they’d borrowed from Digital Gear Corp. “At the moment,” remembers Putman, “most corporations required that we spell our names and pay in money, so we needed to beg, borrow, and steal the instruments to prototype PostScript.”

To keep away from copyright issues, they licensed The Design System ideas from Evans & Sutherland. They had been free to make use of their PARC analysis outcomes, as these had been printed.

Warnock and Geschke weren’t close-mouthed about their plans, and shortly not solely Jobs heard (he was then chairman of Apple Laptop Inc. of Cupertino, Calif.) but in addition C. Gordon Bell, then vice chairman of engineering at Digital Gear in Maynard, Mass. Bell advised the pair that six analysis groups at Digital had been attempting for years to plot a good technique of driving its laser printers, and if Adobe might clear up the issue, Digital can be fascinated about licensing the answer.

Jobs had been dealing with the same drawback. The Macintosh was properly into growth, however with out a letter-quality printer would go nowhere within the enterprise market. Daisy-wheel printers had been out of the query, as a result of they might not produce the bit-mapped graphics fundamental to the Macintosh. However Apple’s personal engineers couldn’t get high-quality graphics out of a laser printer in time for the Macintosh introduction.

Jobs instructed that Adobe change into a software program firm, promote to producers as an alternative of at retail, and negotiate a licensing settlement with Apple.

Undeterred, Jobs and Robert Belleville, then director of engineering for Apple and now director of strategic planning for Convergent Applied sciences Inc., San Jose, Calif., had dreamed up the right Macintosh laser printer—one that might produce all of the fonts on the earth with no assist from a disk drive. However they lacked “the slightest thought of how to do that,” says Belleville, till he bumped into Putman at a cocktail social gathering, heard what Adobe was doing, and introduced Jobs over for a go to.

“I used to be overjoyed!” remembers Belleville. “Their system might do easy issues quick and in addition do full graphics and scanned photos. And once I noticed font scaling was attainable throughout such huge ranges, we had been bought.”

Jobs instructed that Adobe change into a software program firm, promote to producers as an alternative of at retail, and negotiate a licensing settlement with Apple. Adobe preferred the concept, signed the settlement with Apple on the finish of 1983, and far to Hambrecht & Quist’s shock, confirmed a revenue on the finish of its first yr.

Font algorithms

Reimplementing the Jam language with its object orientation, stacks, postfix notation (by which operands precede their operators), and dictionary was comparatively simple. A lot of the analysis had been accomplished at Evans & Sutherland and at PARC. Mainly all Adobe needed to do was engineer it right into a product, named PostScript after the postfix notation it makes use of and since it was to be the very last thing that occurred to a picture earlier than it was printed. Additionally, for the reason that product needed to “Print Something,” it needed to put performance above pace and price—the three elements traded off within the design of microprocessor programs just like the one that might management the laser printer, explains Putman, now vice chairman of engineering at Adobe. Nonetheless, two key breakthroughs remained to be made.

Considered one of them was creating the font algorithms, proprietary formulation for the creation of textual content. “Even with Interpress,” says William Paxton, director of superior growth for Adobe, “fonts had been a wart on the facet of an in any other case elegant design.” Interpress might do arbitrary transformations, like scale and rotate, on photos, however in its early variations couldn’t do them on bit-mapped textual content with out degrading its high quality.

PostScript, nevertheless, unifies textual content and graphics by storing the fonts as define representations of the letters, not as bit maps. Again in early 1983, nevertheless, this unification was simpler to suggest than to understand. “Getting high-quality fonts from define representations of characters was seen as an insoluble drawback,” Warnock says, as a result of it was laborious to supply clean curves of various widths with out jagged edges. Print high quality appeared unobtainable from something lower than a phototypesetter.

However in mid-1983, Warnock says, he had an thought for a basically new set of algorithms which may do the trick. His preliminary experiments promised success, so he set Paxton to refining the algorithms. The outcomes are proprietary and are encrypted contained in the ROMs that comprise PostScript directions as a result of this font expertise is the important thing distinction between Adobe’s product and others.

So profitable was Adobe’s answer to the font drawback that Linotype, Letraset, and different homeowners of the most well-liked typeface designs had been keen for the primary time to license the define representations of their typefaces. No earlier expertise had carried out them justice. (Sarcastically, Adobe is now licensing its font expertise to Linotype, and Linotype is changing its total library of some 2000 fonts into PostScript representations.)

Adobe’s different technical breakthrough is the algorithm, known as Reducer, that breaks down complicated shapes into less complicated ones simpler for PostScript to explain. Such an algorithm is a key element of any graphics language, and theoretical papers a few common type of it had been quite a few: however, says Brotz, “they tended to gloss over the laborious instances that come up in actual functions—figures with giant quantities of knowledge and a number of intersections on the identical level, for instance.” So when the web page printed, sure photos would come out badly fragmented or warped, violating Adobe’s “Print Something” rule.

“A few week after I had joined Adobe in 1983,” Brotz remembers, “John Warnock talked about this quite necessary algorithm that needed to be written. And I, with no graphics background, volunteered. A number of months later, older and wiser, I spotted it actually was one of many world’s hardest issues.”

However Brotz didn’t quit, and he says, “Now we have now an precisely right reducer algorithm. It’s the coronary heart of the graphics system in PostScript.” And a tally Brotz retains reveals that no bugs have been found within the Reducer in additional than two years.

“Warnock promptly labeled [the procedure] ‘Andy’s Silly Enter System’….[but] it turned out that Andy’s Silly Enter System was the bottom frequent denominator and all of the special-case code might disappear.” —Douglas Brotz

Adobe had agreed to ship its software program for set up into the LaserWriter throughout the summer season of 1984. However due to advertising and manufacturing considerations, the LaserWriter itself was to be launched in January of 1985. So the Adobe engineers used the time to tighten the code (the ultimate launch contained some 200,000 bytes) and fine-tune the algorithms. In addition they made some extra particular modifications.

One needed to do with dealing with enter units. As initially conceived, PostScript was to have been impartial of the output, however not the enter, gadget. Warnock had thought that PostScript, to absorb scanned photos, would want to comprise details about a variety of optical scanners. However Brotz, after programming the parameters of simply two of many scanner sorts, realized that the duty was not solely horrendous and repetitive however ate up loads of reminiscence.

Andy Shore, an Adobe pc scientist, overheard him complaining in the future and instructed writing a PostScript process that might faux that it was an enter gadget and spit out the picture data in an ordinary format, whatever the traits of the particular normal. Brotz didn’t assume it will work and “Warnock promptly labeled it ‘Andy’s Silly Enter System.’”

Nonetheless, Brotz thought it is perhaps useful for producing take a look at patterns, and when he applied it, “it turned out that Andy’s Silly Enter System was the bottom frequent denominator and all of the special-case code might disappear.” Issues come up solely when the picture information has been compressed for transmission or storage; the programmer then has to insert a routine to decompress the information earlier than it’s handed to the picture algorithm.

One other enchancment concerned efficiency profiling—working numerous assessments to see what steadily used capabilities slowed down operation. Floating-point routines had been the chief culprits as a result of they’re computationally intensive. So the group took among the algorithms for the frequent operations, equivalent to breaking curves into vectors and drawing outlines, and rewrote them in much less versatile fixed-point arithmetic. Now solely when fixed-point arithmetic can be too imprecise does the interpreter name the floating-point routine.

“So with no lack of generality,” says Edward Taft, Adobe senior pc scientist, “we had been dealing with 99 % of the instances 5 instances quicker than we had been earlier than.”

To enhance the opposite 1 %, Belleville despatched one in every of his engineers over from Apple—Jerome Coonen, a acknowledged knowledgeable in floating level. He optimized the algorithms so, Taft says, “whereas previously an algorithm required six multiplies, 4 divides, and three sq. roots, now it solely required three multiplies, 4 divides, and a few approximation of a sq. root.”

“We got here from the varsity of thought that software program is delicate. So if in case you have issues, you simply have one other launch. However Apple was telling us, ‘Hey, we all the time ship our system in ROM, why can’t you?’” —Douglas Brotz

All through the design of PostScript, pace was recurrently traded off to make sure that any picture would print. The group reasoned that in the event that they in-built all this performance, they might finally enhance the efficiency; but when they unnoticed capabilities, they may by no means have the ability to add them again in.

Nevertheless, says Putman, typically they’d doubts. In order that they designed a model of PostScript that spat out data as quick because the laser moved throughout the web page. The expense of the body buffer was eradicated—together with the power to print pages too difficult for the software program to course of in time.

Adobe known as this implementation Subscript, however dropped it after six months. As Taft says, “Should you’re attempting to advertise an ordinary, there’s nothing worse than issuing a subset of the usual. It implies that all the functions are going to be focused to the bottom frequent denominator.”

Debugging all through the venture was strenuous as a result of the Adobe group was “petrified of placing all this code out on ROMs,” Brotz says. “We got here from the varsity of thought that software program is delicate. So if in case you have issues, you simply have one other launch. However Apple was telling us, ‘Hey, we all the time ship our system in ROM, why can’t you?’”

In January of 1985 the Apple LaserWriter was launched, just about bug-free. In 1984, Adobe signed licensing agreements with QMS Inc., Linotype, and Dataproducts Corp. Right now, even Hewlett-Packard Co., whose PCL web page description language was one in every of PostScript’s earliest opponents, is among the many 23 corporations providing PostScript interpreters for his or her printers.

Low-cost pays off

Though the Adobe group made some key technical breakthroughs, three different parts had been essential to make PostScript a runaway success not simply in low-volume skilled publishing however within the high-volume workplace surroundings.

As famous earlier, one was an inexpensive laser printer. When Adobe was based, the most cost effective price round $10,000. It additionally weighed as a lot as a desk, in order that it needed to be serviced on web site and bought by a distributor, not on a cash-and-carry foundation. Then Canon Inc., of Tokyo, Japan, launched the Canon LBP-CX desktop laser printer, which, furthermore, printed superbly. “If it had been poor xerography,” says Paxton, “it wouldn’t have mattered how good our expertise was.”

Additionally on the horizon was a bit-map-based private pc—the Apple Macintosh. All earlier low-cost private computer systems had used character graphics, for which daisy-wheel printers made extra sense.

“The projections had been that the RAM costs had been going to drop, however you needed to have a really sturdy abdomen to have the ability to go as much as the wall and pray that the door was going to open.”—William Paxton

The third piece of luck was the decline within the worth of reminiscence chips. “We began this growth on an uneconomic foundation,” Warnock says. “The LaserWriter’s first controller wanted forty-eight 256K DRAM chips, which as much as December of 1984 price about $30 every. That meant Apple would have needed to promote that machine for about $10,000—however its pc price $2400.”

However, with Belleville’s and Jobs’s sturdy help, the Adobe group wager that the reminiscence course of would drop. “Certain,” says Paxton, “the projections had been that the RAM costs had been going to drop, however you needed to have a really sturdy abdomen to have the ability to go as much as the wall and pray that the door was going to open.”

Warnock feedback, “Most corporations will solely take care of present-day expertise and identified prices. The brilliance of Steve Jobs is that he’ll say, ‘There shall be this chip popping out at that worth level at the moment, and I’ll design my product to make use of it.’” And certainly, when the LaserWriter was introduced in January of 1985, 256K RAMs price about $4 every and the printer may very well be priced at $6995.

Right now, some 40 corporations have introduced their tools is appropriate with PostScript and that their interpreters run quicker and price lower than Adobe’s model. They can not supply the identical font library, however they are saying they’ve fonts and font algorithms nearly as good as Adobe’s. At this writing, nevertheless, none of those corporations had apparently shipped a PostScript clone to a buyer, they usually reportedly have discovered it tougher to copy Adobe’s work than they’d anticipated.

Once they do lastly ship, and if they will interpret 80 or 90 % of PostScript applications, Adobe is resigned to dealing with “good old school American competitors,” says Geschke. The corporate has no patents to defend, solely copyrights and commerce secrets and techniques, so if different corporations can reproduce Adobe’s expertise, it has no authorized recourse. “Essentially the most we will do is to proceed to enhance our expertise,” Geschke says.

What’s NeXT?

Adobe’s newest technical breakthrough, demonstrated in San Francisco in January, is a model of PostScript that controls photos on a pc display screen in addition to on a printed web page. Known as Show PostScript, this product is the primary to offer device-independent graphics for pc screens.

Show PostScript, like the unique PostScript printer protocol, had a nudge from Jobs. His new firm, NeXT Inc., Palo Alto, Calif., labored with Adobe to develop it, and will probably be the graphics normal for all NeXT’s computer systems. Digital Gear has already licensed Show PostScript for its DEC Home windows workstation structure. If different main corporations observe, Adobe may very well be properly on the best way to setting its second normal.

To probe additional

All the pieces a programmer or consumer would possibly need to know concerning the PostScript language is supplied in “PostScript Language Tutorial and Cookbook“ and “PostScript Language Reference Guide,” each written by Adobe Programs Inc. and printed by Addison Wesley Publishing Co. (New York, 1985). As well as, Adobe periodically publishes a publication, “Colophon,” with programming ideas and information about PostScript merchandise.

Interpress, the web page description language from Xerox Corp.’s Palo Alto Analysis Heart (PARC) that preceded PostScript within the laboratory however adopted it within the market, is described within the June 1986 concern of IEEE’s journal, Laptop (pp. 72-77). For extra data on Xerox PARC, see “Contained in the PARC: the ‘data architects,’” Spectrum, October 1985, p. 62.

“Window on PostScript” in MacWeek, Feb. 2, 1988, pp. 28-29, comprises a dialogue of opponents’ makes an attempt to clone the language.

Replace April 2022: Whereas most dwelling and workplace printers depend on different web page description languages today, PostScript stays the selection of graphics artists and industrial printers for its capability to precisely produce complicated photos. And the ever present Transportable Doc Format (PDF) is predicated on PostScript.

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