User talk:Copyeditor42

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Hex exponent notation

Hi. I have a question regarding an old edit of yours ([1]) where you added information about a hex exponent notation using a "p" letter to denote "*2^". Can you provide additional information where this notation is used or by whom it was proposed? I am aware of a very similar notation using an uppercase "B" for exactly the same purpose, and have also seen implementations (in calculators) using a lowercase "b", but never a "p" (although this would avoid any possible ambiguity with the base of the mantissa). Can you provide a source for this and/or narrow this down in time?
Thanks --Matthiaspaul (talk) 23:58, 29 August 2015 (UTC)[reply]

The "p" notation is required by IEEE standard 754-2008 for floating-point systems. It's also required by the Single Unix Specification (IEEE standard 1003.1, aka. POSIX) for the %a specifier in the printf family of functions.

It's been in printf for ages -- at least 20 years for the GNU printf, which may have been the first to introduce the notation (if it was not the 1985 version of IEEE 754).

See the POSIX man-page http://pubs.opengroup.org/onlinepubs/9699919799/functions/printf.html for the %a specifier.

I have never seen any other hex exponential notation on machines within the last 35 years; and 'b' or 'B' would certainly be ambiguous within the significand.

Copyeditor42 (talk) 10:28, 2 September 2015 (UTC)[reply]