Amateur     Extra   7 Query tools (since 2003-2004)

Dean Gibson's Amateur Radio Tools

The Story of Zero

Once upon a time, CW radio operators wrote zeros with a slash, to distinguish them from the uppercase letter "oh" (especially in callsigns). Other digits (e.g., seven) were sometimes also written this way. This was a fine convention for many years.

However, time marches on, and along came the computer. Early computer designers (e.g., IBM) also understood this problem, and sometimes also rendered a zero with a slash, or a dot in the center (e.g., the original IBM EGA and VGA cards). Other variations were to make the uppercase "oh" glyph wider than the "zero" glyph, or to make all the digits slightly taller, etc. So far, so good.

However, time continues to march on, and along came those who thought that just because they could write a BASIC program or layout a printed circuit board, that they were "computer experts" and could ignore what others had learned over the years (there's a word for this; it's called "experience"). In particular, they didn't see the need for that ugly slash or dot, so they produced junk (in more ways than one) that fit their narrow vision of the world. Many of these new computer world "experts" designed fonts that not only had indistinguishable "zero" and uppercase "oh" glyphs, they also had indistinguishable "one" and lowercase "ell" glyphs (there's also a word for this; it's the opposite of "smart").

Now back to our story: Radio operators, particularly CW radio operators, are an obstinate bunch. So when their favorite slashed zero glyph was not present in the local ASCII font on their PCs, they went looking for it.

Under DOS, they found it as the non-ASCII character Alt-237, rendered as "Φ". This was particularly ugly, since it was a Greek letter (officially, "Greek uppercase letter phi") rather than a slashed ASCII zero, but the radio operators didn't care. Under Windows, they found it as the non-ASCII character Alt-216, rendered as "Ø". This wasn't a good match either, since it was a Latin letter (officially, "Latin uppercase letter O with stroke") rather than a slashed ASCII zero, and was typically rendered as a wider glyph than the zero ("0") glyph (digit glyphs are usually a uniform width in order to make columnar display of numbers readable), but the radio operators still didn't care.

Now comes the bad news. It's one thing for radio operators to use a non-ASCII character that renders as slashed "oh" glyph in place of a zero glyph in the privacy of their own homes, but it's another thing to attempt to use it in communications with the US government, as several radio operators have found out, to their detriment: If you file a vanity callsign application with the FCC and use any character other than ASCII zero in place of zero, your choice of that callsign will be summarily rejected.

It's also a bad idea on web pages to replace an ASCII zero with another (non-ASCII) character that renders as a slashed glyph, as this can interfere with screen reader software (which only sees the underlying non-ASCII character and not the glyph) that is often used by those who are visually impaired. It also interferes with the "cut-and-paste" of any callsign with such a character, into any FCC application or callsign lookup page (the callsign won't be found).

For this reason, these web pages specify the "Monaco" font for displaying callsigns. If you have the "Monaco" font installed, you will see slashed zero (not slashed "oh") glyphs in callsigns, and the underlying character will be an ASCII zero (thusly: 0). The "Monaco" font is available for download here.

Moral: If you want a fixed-pitch font that renders an ASCII zero character as a slashed zero glyph, try "Monaco". If you also want a font without a slashed zero glyph, but would like different glyphs for "zero", uppercase "oh", "one", and lowercase "ell", try "Tahoma". In any case, use ASCII zero for zero and don't mess with Mother ASCII.