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From: poynton%vector@Sun.COM (Charles Poynton)
Newsgroups: comp.sys.next,sci.electronics,rec.ham-radio
Subject: Unit nomenclature (Was Disk transfer speed)
Summary: k=1000, K=1024, b=bit, B=Byte to avoid confusion; m isn't mega.
Message-ID: <76349@sun.uucp>
Date: 6 Nov 88 06:16:09 GMT
References: <938@ccnysci.UUCP> <8810250344.AA02429@esplanade.csri.toronto.edu> <7255@dasys1.UUCP>
Sender: news@sun.uucp
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I propose some nomenclature which might reduce the incidence of confusion
about data rates which has surrounded the recent SCSI discussions on
comp.sys.next.

First, international standards.

Upper case "M" is the symbol for mega, a multiplier of 1000000.  Little-m
is the symbol for milli, 1/1000, and care should be taken not to confuse
it with mega.

Lower-case "k" is the internationally-standardized symbol for kilo, a
multiplier of 1000.  Its being lower case is the exception:  all other
multipliers greater than unity have upper-case symbols, and ALL
multipliers less than unity have lower-case symbols.  [The Greek symbol
micro is for a multiplier of 1/1000000; but the letter "u" can be
substituted without confusion.]

Lower-case "s" is the symbol for second:  upper case unit symbols are
reserved for units named after individuals, such as "S" for Mr Siemen,
"Hz" for Mr Hertz, or "B" for the unit bel [sic], named after Mr Bell.
The full name of a unit itself is NOT capitalized whether derived from a
proper name or not.

Proper form places a space between the numeric value and the multiplier,
no space between the multiplier and the base unit, and no hyphens
anywhere.

Now, my proposals.

I suggest adopting upper-case K for 1024.  This does not conflict with any
international symbols.  The use of this upper-case letter is somewhat
mnemonic, in that the 1 K is a little larger than 1 k.  [The unit symbol K
is for kelvin, the unit of absolute temperature, but this is a unit and
not a multiplier symbol so there's no conflict.]

I suggest using lower-case "b" for bit, and upper-case "B" for Byte.
Neither conflicts with any metric symbols.  I use "w" for "word", whose
width is context-dependent.  [Lower case distinguishes it from the weber,
symbol Wb.]

For those who measure data communications rates, all but the most esoteric
uses of the unit "baud" should more properly use bits per second, symbol
"b/s".  All conventional data communications rates are related to 1000
[and not to 1024], for example, 9.6 kb/s.

Big-M is problematic.  My custom is to use M for both 1000000 and
1024*1024, and let context determine the interpretation.  Little-m, milli,
should certainly not be confused with either of these.  Rates are nearly
always referenced to decimal mulipliers (for example, SCSI 4.8 MB/s, audio
44.1 Mw/s).  Multiples of 1024 are generally restricted to describing
capacity.


Charles Poynton
poynton@sun.com