Path: news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: "A diagram of C23 basic types"
Date: Thu, 26 Jun 2025 17:10:48 -0700
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scott@slp53.sl.home (Scott Lurndal) writes:
[...]
> But not all decimal floating point implementations used "hex floating point".
>
> Burroughs medium systems had BCD floating point - one of the advantages
> was that it could exactly represent any floating point number that
> could be specified with a 100 digit mantissa and a 2 digit exponent.

BCD uses 4 bits to represent values from 0 to 9.  That's about 83%
efficent relative to pure binary.  (And it still can't represent 1/3.)

Another option (I think IBM has implemented this) is to use 10 bits
to represent values from 0 to 999, taking advantage of the nice
coincidence that 2**10 is barely bigger than 10**3.  That's more
than 99.6% efficient relative to pure binary.  Of course it's still
more complicated to implement.

[...]

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */