The GSI C/A/T (Computer Assisted Typesetter) is a phototypesetter developed by Graphic Systems in 1972. This phototypesetter, along with troff software for UNIX, revolutionized the typesetting and document printing industry. Phototypesetting is most often used with offset printing technology.
The GSI C/A/T phototypesetter was marketed by Singer Corporation in 1974 and later the company was purchased by Wang Laboratories in 1978.
Graphic Systems designed a simple computer front-end to print basic text as display type. Full scale page composition computing was designed at Bell Laboratories as part of the UNIX project.
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The C/A/T phototypesetter has the following features:
C/A/T optics consist of a rotating wheel to which are attached film strips of master font characters. There are four such replaceable font film strip sections on the periphery of the wheel. A xenon strobe inside the wheel is programmed to flash the characters from the font films through magnification optics to a fiber-optic bundle. The programmable location of the fiber-optic bundle determines the horizontal position of the character image on a scroll of photographic paper or film.
C/A/T is a highly addressable phototypesetter with full optics control from computer generated data. This precise control of optics and image position makes the interface to computer programs reasonably simple. Data is normally transmitted to the C/A/T by paper tape. Some companies created electronic replacements for the paper tape interface to accommodate direct connection to computer systems. C/A/T has no page layout and pagination capability. It is only a high resolution printer that puts high-resolution character images onto a photographic media. Page layout is determined by the typesetting software used to generate the paper tape.
Bell Labs purchased a C/A/T phototypesetter in 1973 for their engineers who were developing the UNIX operating system. The C/A/T phototypesetter became the defacto standard for UNIX based typesetting. The early typesetting programs on general purpose computers were displacing special purpose photocomposition systems.
Noteworthy typesetting software created for the C/A/T include troff (1973), which was developed by Joe F. Ossanna at Bell Labs. Brian Kernighan later developed the ditroff (typesetter independent troff) program which supports the C/A/T and other publishing systems. C/A/T was the workhorse of UNIX printing through the 1980s for those shops that could not afford hot lead typography equipment or expensive and proprietary document typesetting systems. High resolution laser printing, now common in desktop publishing, was not yet available.
Graphic Systems did not have the marketing capability to satisfy the growing demand of the phototypesetting business. Singer Manufacturing Company around 1975 acquired the rights to market the hardware, including placing the Singer C/A/T logo on the products. Singer continued to support C/A/T systems until 1979. Graphic Systems was bought by Wang Laboratories in 1978. The phototypesetter was then known as the Wang Graphic Systems C/A/T with continued support through the 1980s.
Advances in the electronic typesetting programs like ditroff by Brian Kernighan (1979), TeX by Donald E. Knuth (1979), and LaTeX by Leslie Lamport (1981–1983) finally allowed the C/A/T phototypesetter to become obsolete. The C/A/T phototypesetter continued to be prevalent in many UNIX based documentation shops until high quality laser printers became prevalent in the marketplace.
Others had noticed the sudden growth in the typesetting equipment market. One was Singer Corp. which set up a national sales force for typesetting and graphic arts equipment, including the phototypesetting machines made by another Massachusetts company, Graphic Systems Inc. These machines had a brief but spectacular run in the 1970s until someone at Singer asked what they were doing in the typesetting equipment business (which they knew nothing about), so little GSI was left to its own devices with no marketing organization. Singer had been responsible for providing the type font masters and the machines were getting a reputation for poor base line regularity. This may have been a hardware problem because strobe timing errors showed up as base line errors on the GSI machines, while on the Mergenthaler VIP such errors showed up between the characters, and unless fairly serious, escaped notice. GSI began producing excellent font masters and the machines continued to find a market. They built a minicomputer into the machine (a Nova), making it capable of setting justified, hyphenated type from a pure text input using a particularly convenient coding system that owed nothing to old Linotype practices. It allowed stored formats, or in-line codes. These machines held four fonts at a time, but had more characters per font than the VIP, so that the asterisks and other common characters were included. They used a rotating turret of lenses and a second "doubler lens" to offer a range of sizes from 5 to 72 points. The GSI machines were particularly popular with the in-house typesetting departments that began to grow in most larger companies.
— Clark E. Coffee, Old Phototypesetter Tales[2]