Raster CRT Typography – the glyphs drawn by DEC VT100 and VT220 terminals #Typography #DEC #VintageComputing #Fonts

Via mass:werk blog:

Recently, I engaged in a bit of analog media emulation, namely for the purpose of the reenactment of raster CRT graphics as seen on “glass terminals” like the iconic VT-series by the Digital Equipment Corporation (DEC). An endeavor, which raises a few questions, like, is there anything special to the media, what did the fonts really look like, and can we reconstruct them from specifications?

Thanks to a tiny wealth of technical information available on the web, at sites like vt100.net and bitsavers.org, determining the look of these fonts should be easy. E.g., we may reconstruct the glyphs from the terminals’ ROMs. This way, we should be able to determine their exact forms. There are even TrueType-fonts available, meant to recreate the typography of the VT220, “Glass TTY VT220,” including scanlines, and “DEC Terminal Modern” with modernized, smooth outlines:

VT220 TrueType fonts
Modern TrueType fonts recreating the glyphs of the VT220. Mind that the VT-terminals supported two resolution modes, one at 132 characters per line and one at 80 characters (char-matrix 9×10 and 10×10, respectively), the latter introducing an extra spacing of one pixel.

Having a closer look at the two fonts, there are some notable differences (the differences in spacing may be explained by the two characters per line modes of the VT-terminals), however, neither looks right. Comparing them to photos of the similar VT100, there are discernible differences, not only in the font weight, but also in the size and form of the contours and the overall “feel” of the font. However, the apparent confusion about the weight of the font isn’t especially helped by photos of the real thing either, as the impression conveyed by them differs widely by lens, exposure and camera settings used.

VT100 displaying Adventure / Colossal Cave.
VT100 displaying Adventure / Colossal Cave Photo: Wikipedia, Dave Fischer, 2008, Wikimedia Commons (edited, N.L.).

ROMs

Since ROMs are available, we may start there, since they are the closest, we may get, to the real thing, aren’t they? What could possibly go wrong?

VT100 and VT220 separated characters as in ROM

Now, this doesn’t look right either. Obviously, the glyphs will be rendered stretched vertically to about double height, but there’s more going on here. The characters just don’t look right. P.e., have a closer look at “p” and “q” or the offset in the dots of the downward right stroke of “k”, not to speak of the funny digits “6” and “9” of the VT100 or the distorted “2”! Moreover, at a closer look, the character matrix is just 8×10, while we expected at least 9×10 (and 10×10 for 80-cols mode) — as described in the specifications. Clearly, this is not what is displayed on the screen.

See the rest of the article including the author’s take on recreating the fonts.

Ed. note: hopefully such fonts can be used in PyPortal and other recreations of vintage electronics.

Are you a vintage terminal/computer fan? Let us know in the comments below.


Adafruit publishes a wide range of writing and video content, including interviews and reporting on the maker market and the wider technology world. Our standards page is intended as a guide to best practices that Adafruit uses, as well as an outline of the ethical standards Adafruit aspires to. While Adafruit is not an independent journalistic institution, Adafruit strives to be a fair, informative, and positive voice within the community – check it out here: adafruit.com/editorialstandards

Join Adafruit on Mastodon

Adafruit is on Mastodon, join in! adafruit.com/mastodon

Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, TinyGO, or even use the Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for CircuitPython, MakeCode, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.

Have an amazing project to share? The Electronics Show and Tell is every Wednesday at 7pm ET! To join, head over to YouTube and check out the show’s live chat – we’ll post the link there.

Join us every Wednesday night at 8pm ET for Ask an Engineer!

Join over 36,000+ makers on Adafruit’s Discord channels and be part of the community! http://adafru.it/discord

CircuitPython – The easiest way to program microcontrollers – CircuitPython.org


Maker Business — “Packaging” chips in the US

Wearables — Enclosures help fight body humidity in costumes

Electronics — Transformers: More than meets the eye!

Python for Microcontrollers — Python on Microcontrollers Newsletter: Silicon Labs introduces CircuitPython support, and more! #CircuitPython #Python #micropython @ThePSF @Raspberry_Pi

Adafruit IoT Monthly — Guardian Robot, Weather-wise Umbrella Stand, and more!

Microsoft MakeCode — MakeCode Thank You!

EYE on NPI — Maxim’s Himalaya uSLIC Step-Down Power Module #EyeOnNPI @maximintegrated @digikey

New Products – Adafruit Industries – Makers, hackers, artists, designers and engineers! — #NewProds 7/19/23 Feat. Adafruit Matrix Portal S3 CircuitPython Powered Internet Display!

Get the only spam-free daily newsletter about wearables, running a "maker business", electronic tips and more! Subscribe at AdafruitDaily.com !



No Comments

No comments yet.

Sorry, the comment form is closed at this time.