Reviving the Hershey fonts

At the 2015 edition of TypeCon in Denver, Adobe's Frank Grießhammer presented his work reviving the famous Hershey fonts from the Mid-Century era of computing. The original fonts were tailor-made for early vector-based output devices but, although they have retained a loyal following (often as a historical curiosity), they have never before been produced as an installable digital font.

Grießhammer started his talk by acknowledging his growing reputation for obscure topics—in 2013, he presented a tool for rapid generation of the Unicode box-drawing characters—but argued that the Hershey fonts were overdue for proper recognition. He first became interested in the fonts and their peculiar history in 2014, when he was surprised to find a well-designed commercial font that used only straight line segments for its outlines. The references indicated that this choice was inspired by the Hershey fonts, which led Grießhammer to dig into the topic further.

The fonts are named for their creator, Allen V. Hershey (1910–2004), a physicist working at the US Naval Weapons Laboratory in the 1960s. At that time, the laboratory used one of the era's most advanced computers, the IBM Naval Ordnance Research Calculator (NORC), a vacuum-tube and magnetic-tape based machine. NORC's output was provided by the General Dynamics S-C 4020, which could either plot on a CRT display or directly onto microfilm. It was groundbreaking for the time, since the S-C 4020 could plot diagrams and charts directly, rather than simply outputting tables that had to be hand-drawn by draftsmen after the fact.

By default, the S-C 4020 would output text by projecting light through a set of letter stencils, but Hershey evidently saw untapped potential in the S-C 4020's plotting capabilities. Using the plotting functions, he designed a set of high-quality Latin fonts (both upright and italics), followed by Greek, a full set of mathematical and technical symbols, blackletter and Lombardic letterforms, and an extensive set of Japanese glyphs—around 2,300 characters in total. Befitting the S-C 4020's plotting capabilities, the letters were formed entirely by straight line segments.

The format used to store the coordinates of the curves is, to say the least, unusual. Each coordinate point is stored as pair of ASCII letters, where the numeric value of each letter is found by taking its offset from the letter R. That is, "S" has a value of +1, while "L" has a value of -6. The points are plotted with the origin in the center of the drawing area, with x increasing to the right and y increasing downward.

Typographically, Hershey's designs were commendable; he drew his characters based on historical samples, implemented his own ligatures, and even created multiple optical sizes. Hershey then proceeded to develop four separate styles that each used different numbers of strokes (named "simplex," "duplex," "complex," and "triplex").

The project probably makes Hershey the inventor of "desktop publishing" if not "digital type" itself, Grießhammer said, but Hershey himself is all but forgotten. There is scant information about him online, Grießhammer said; he has still not even been able to locate a photograph (although, he added, Hershey may be one of the unnamed individuals seen in group shots of the NORC room, which can be found online).

Hershey's vector font set has lived on as a subject for computing enthusiasts, however. The source files are in the public domain (a copy of the surviving documents is available from the Ghostscript project, for example) and there are a number of software projects online that can read their peculiar format and reproduce the shapes. At his GitHub page, Grießhammer has links to several of them, such as Kamal Mostafa's libhersheyfont. Inkscape users may also be familiar with the Hershey Text extension, which can generate SVG paths based on a subset of the Hershey fonts. In that form, the paths are suitable for use with various plotters, laser-cutters, or CNC mills; the extension was developed by Evil Mad Scientist Laboratories for use with such devices.

Nevertheless, there has never been an implementation of the designs in PostScript, TrueType, or OpenType format, so they cannot be used to render text in standard widgets or elements. Consequently, Grießhammer set out to create his own. He wrote a script to convert the original vector instructions into Bézier paths in UFO format, then had to associate the resulting shapes with the correct Unicode codepoints—Hershey's work having predated Unicode by decades.

The result is not quite ready for release, he said. Hershey's designs are zero-width paths, which makes sense for drawing with a CRT, but is not how modern outline fonts work. To be usable in TrueType or OpenType form, each line segment needs to be traced in outline form to make a thin rectangle. That can be done, he reported, but he is still working out what outlining options create the most useful final product. The UFO files, though, can be used to create either TrueType or OpenType fonts.

When finished, Grießhammer said, he plans to release the project under an open source license at github.com/adobe-fonts/hershey. He hopes that it will not only be useful, but will also bring some more attention to Hershey himself and his contribution to modern digital publishing.