CAT (phototypesetter)

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 before 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.

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. The wheel's periphery has four such replaceable font film strip sections. 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 made 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. C/A/T became the de facto standard for UNIX based typesetting. The early typesetting programs on general purpose computers displaced special purpose photocomposition systems.

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