Symbol Font Considered Harmful

Subject: Symbol Font Considered Harmful
From: "Andrew Warren" <awarren -at- synaptics -dot- com>
To: <techwr-l -at- lists -dot- techwr-l -dot- com>
Date: Thu, 2 Nov 2006 18:17:19 -0800

I have a point, but I need about three paragraphs of setup before I can
make it. Fortunately, the rest of this post is so long that by the time
you're done, you'll hardly remember that you had to wade through this

If you work in the electronics industry, you probably know what a
resistor is: It's an electronic component, usually less than a
quarter-inch long and often much smaller, that costs less than a penny
and is found in most electrical circuits.

Resistors are specified by two unrelated parameters: resistance measured
in ohms (symbolized by the greek letter omega) and power rating measured
in watts (symbolized by the letter W), so a typical resistor spec would
be something like "4.7 kiloohms, 1/8-watt" or "4.7k[omega] 1/8W".

Nearly all resistors have a maximum power-handling capacity of half a
watt or less, although there do exist special high-power resistors that
are an inch or two long and surrounded by finned metal heatsinks. These
resistors can handle a lot of power -- 25 W or even 50 W -- but they're
not very common, since there aren't a lot of applications for resistors
that large. In very specialized applications -- dynamic braking of big
electric generators, for example -- there's occasionally a need for a
kilowatt (kW) resistor. A couple of companies make them; they're over a
foot long and very expensive. No one makes megawatt (MW) resistors.


If kilowatt resistors are so rare, and megawatt resistors don't even
exist, how come a Google search for <"kW resistor" OR "MW resistor">
returns 10,000 hits?

Well, partly it's because "MW resistor" also picks up the small-m
version, which stands for "milliwatt resistor", but mostly it's because
people put "ohm" symbols in their documents by inserting the omega
character from the Symbol font.

The "omega" in the Symbol font is mapped to the same character code as
the "W" in other fonts. Google ignores font information in its text
searches, so when it indexes a page, it sees a "W" wherever there's a
Symbol-font "omega".

That's not such a big deal, but look at the other disasters this causes:

If you're viewing the document in a web browser that's been
configured to use your favorite fonts rather than the fonts
specified by the document, the omega symbols become Ws.

If you don't use your own fonts, the omegas will probably look
fine in your browser... But as soon as you cut-and-paste from
the browser window to another application, like Frame or Word,
the omegas become Ws.

If you send the document through an email system that strips
HTML, the omegas become Ws.

If you send it to a printer that doesn't have the Symbol font,
the omegas become Ws.

If you view it on a computer that doesn't have the Symbol font,
the omegas become Ws.

In most of these cases, the font information is permanently lost once
the document's omega symbols become Ws. They never switch back, even if
the document is subsequently viewed in a system which CAN display HTML
or the Symbol font.

The W-instead-of-omega problem isn't limited to web pages; I see it ALL
THE TIME in published datasheets, application notes, user's manuals,
trade journal articles, etc.

Fortunately, the error is easy to spot, since the erroneous "W" usually
makes no sense, and the intended meaning can generally be deduced from
the context.


There's another error commonly caused by use of the Symbol font, and

The Greek letter "mu" is often used in engineering and scientific
writing to represent the prefix "micro-" (one millionth). In the old
days, before we all had access to fancy computer typefaces, typewritten
documents would use the lowercase "u" instead of "mu", since the two
letters look very similar.

"Lowercase 'u' means 'mu' means 'micro-'" was a universally-understood
convention (among engineers and scientists, anyway): usec =
microseconds, uF = microfarads, uA = microamps... Even uP =
microprocessor. No one was ever confused by this, and all was well
until some pedantic dumbass noticed that he could make his unit names
"correct" by using the Symbol-font "mu" instead of the lowercase "u"
that we'd all been happy with for decades.

The result, of course, is the same as for "omega", with one small but
fatal difference. "Omega" maps to the "W" character, which almost
always looks like an error, but "mu" maps to the "m" character, which is
the symbol for the prefix "milli-" (one thousandth).

Since "m-for-milli" can be reasonably used almost anywhere that
"mu-for-micro" can, it NEVER looks like an error!

You thought NASA's metric-vs-English mistakes were boneheaded? In those
cases, numbers were off by a factor of 4.45, but when the mu-to-m error
occurs, everything gets multiplied by 1000! Microseconds become
milliseconds, microamps become milliamps, micrometers become
millimeters... And there's NO WAY TO TELL that the error happened unless
there's a LOT of context that happens to look self-contradictory.

Since it's so hard to identify the mu-to-m error, it's difficult to know
how prevalent it is, but I'd guess that it happens at least as
frequently as the omega-to-W error that I see everywhere.

There are actually a few places where a mu-to-m error would be obvious,
and I often see it there... Like, for instance, in the US Navy's NRaD
Writing and Editorial Guidelines:

It contains a list of abbreviations that includes both micro- and milli-
units. It's obvious that a mu-to-m error has occurred, since the list
shows "m" for both sets of units.

I no longer approve documents that use the Symbol font for any purpose.
I now insist that "micro-" be either spelled out or represented by the
lowercase "u", and "ohm" either gets spelled out or omitted ("4.7k
resistor" or "4k7 resistor" are both well-understood in my industry to
mean "4.7 kiloohm resistor").

Every once in a while, someone actually needs a real "micro" or "ohm"
symbol in his document. In those cases, I'm okay -- barely -- with the
use of Unicode "micro" (U+00B5, ALT-0181) and "ohm" (U+2126, ALT-8486)
or "omega" (U+03A9, ALT-0937) characters from whatever regular font he's

Of course, when those Unicode characters get stripped by an ASCII-only
email system or the document's converted to a font that doesn't contain
those Unicode glyphs, the symbols will still disappear or be converted
to an ampersand or a copyright symbol or a little black box with a
question mark in it or something... But at least they won't masquerade
as reasonable-but-totally-wrong characters that are going to cost my
company a ton of money or injure someone.


=== Andrew Warren - awarren -at- synaptics -dot- com
=== Synaptics, Inc - Santa Clara, CA

WebWorks ePublisher Pro for Word features support for every major Help
format plus PDF, HTML and more. Flexible, precise, and efficient content
delivery. Try it today!

Easily create HTML or Microsoft Word content and convert to any popular Help file format or printed documentation. Learn more at

You are currently subscribed to TECHWR-L as archive -at- infoinfocus -dot- com -dot-

To unsubscribe send a blank email to
techwr-l-unsubscribe -at- lists -dot- techwr-l -dot- com
or visit

To subscribe, send a blank email to techwr-l-join -at- lists -dot- techwr-l -dot- com

Send administrative questions to admin -at- techwr-l -dot- com -dot- Visit for more resources and info.


Previous by Author: RE: dangers of spellcheck
Next by Author: RE: Symbol Font Considered Harmful
Previous by Thread: Adobe Acrobat 8 Released
Next by Thread: Question on Working With a New Documentation Supervisor - Please Help

What this post helpful? Share it with friends and colleagues:

Sponsored Ads