I wrote:
"Your 4.7004 bits example is impossible. There can only ever be an
integral number of on/off states."
Euric replied:
Euric replied:
"I gave such an example? I don't recall giving such an example.
Of course there can only be an integral number of bits. That could be
specified in the definition of the bit. There can be 4.700 4 Mibit or
4.700 4 Mbit."
Indeed, you did -- in the paragraph you quoted from Rowlett in USMA 27962. When you quote sources, perhaps you should read what they say first. <g>
Indeed, you did -- in the paragraph you quoted from Rowlett in USMA 27962. When you quote sources, perhaps you should read what they say first. <g>
However, in what you say above, you have compounded the error, in that
you're now talking about a non-integer number of mebibits or megabits. You must
do the rounding up first. Thus, 26 possible character values require 5 bits for
their representation. As five bits can be used to represent a total of 32 unique
values, 6 values are simply unassigned in that case.
There is, of course, a 5-level code that uses all 32 possible values, of
which two are reserved for shift characters. That code is International
Telegraph Alphabet No. 2 (ITA-2), which is a variant of Baudot Code. Following a
shift character, 30 of the values have a new meaning (with 2 values still
reserved for the same shift characters (letters shift and figures shift). Thus,
in data transmission (which is the only purpose of ITA-2), you can, in
theory, represent 60 unique characters. (In practice, there are a some
values that mean the same in either shift mode.)
To respond to your "That could be specified in the definition of the bit,"
the answer is no, it couldn't. A bit is a bit is a bit. The fact that there can
only be an integral number is a simple mathematical fact and is implicit, not
specifiable, in the definition.
Bill Potts, CMS
Roseville, CA
http://metric1.org [SI Navigator]
