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C++ proposal: There are exactly 8 bits in a byte

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Re: C++ proposal: There are exactly 8 bits in a byte

#161

Post by boulos »

The current proposal says:

> A byte is 8 bits, which is at least large enough to contain the ordinary literal encoding of any element of the basic character set literal character set and the eight-bit code units of the Unicode UTF-8 encoding form and is composed of a contiguous sequence of bits, the number of which is bits in a byte.

But instead of the "and is composed" ending, it feels like you'd change the intro to say that "A byte is 8 contiguous bits, which is".

We can also remove the "at least", since that was there to imply a requirement on the number of bits being large enough for UTF-8.

Personally, I'd make a "A byte is 8 contiguous bits." a standalone sentence. Then explain as follow up that "A byte is large enough to contain...".

Re: C++ proposal: There are exactly 8 bits in a byte

#162

Post by kstrauser »

Animats wrote: post #54
Quekid5 wrote: post #5

JF Bastien is a legend for this, haha. I would be amazed if there's any even remotely relevant code that deals meaningfully with CHAR_BIT != 8 these days. (... and yes, it's about time.)

Here's a bit of 40 year old code I wrote which originally ran on 36-bit PDP-10 machines, but will work on non-36 bit machines.[1] It's a self-contained piece of code to check passwords for being obvious. This will detect any word in the UNIX dictionary, and most English words, using something that's vaguely like a Bloom filter. This is so old it predates ANSI C; it's in K&R C. It used to show up on various academic s…

Huh, that’s clever!

Re: C++ proposal: There are exactly 8 bits in a byte

#163

Post by __turbobrew__ »

oefrha wrote: post #101
nialv7 wrote: post #57

Earlier quoted context omitted.

well they managed to get two's complement requirement into C++20. there is always hope.

Well then someone somewhere with some mainframe got so angry they decided to write a manifesto to condemn kids these days and announced a fork of Qt because Qt committed the cardinal sin of adopting C++20. So don’t say “a problem literally nobody has”, someone always has a use case; although at some point it’s okay to make a decision to ignore them. https://lscs-software.com/LsCs-Manifesto.html https://news.ycombinat…

This person is unhinged.

> It's a desktop on a Linux distro meant to create devices to better/save lives.

If you are creating life critical medical devices you should not be using linux.

Re: C++ proposal: There are exactly 8 bits in a byte

#164

Post by Maxatar »

elromulous wrote: post #124
poincaredisk wrote: post #110

Earlier quoted context omitted.

A bit is either a 0 or 1. A byte is the smallest addressable piece of memory in your architecture.

Technically the smallest addressable piece of memory is a word.

I don't think the term word has any consistent meaning. Certainly x86 doesn't use the term word to mean smallest addressable unit of memory. The x86 documentation defines a word as 16 bits, but x86 is byte addressable.

ARM is similar, ARM processors define a word as 32-bits, even on 64-bit ARM processors, but they are also byte addressable.

As best as I can tell, it seems like a word is whatever the size of the arithmetic or general purpose register is at the time that the processor was introduced, and even if later a new processor is introduced with larger registers, for backwards compatibility the size of a word remains the same.

Re: C++ proposal: There are exactly 8 bits in a byte

#165

Post by nonameiguess »

gerdesj wrote: post #100
WalterBright wrote: post #90

D made a great leap forward with the following: 1. bytes are 8 bits 2. shorts are 16 bits 3. ints are 32 bits 4. longs are 64 bits 5. arithmetic is 2's complement 6. IEEE floating point and a big chunk of wasted time trying to abstract these away and getting it wrong anyway was saved. Millions of people cried out in relief! Oh, and Unicode was the character set. Not EBCDIC, RADIX-50, etc.

"1. bytes are 8 bits" How big is a bit?

How philosophical do you want to get? Technically, voltage is a continuous signal, but we sample only at clock cycle intervals, and if the sample at some cycle is below a threshold, we call that 0. Above, we call it 1. Our ability to measure whether a signal is above or below a threshold is uncertain, though, so for values where the actual difference is less than our ability to measure, we have to conclude that a bit can actually take three values: 0, 1, and we can't tell but we have no choice but to pick one.

The latter value is clearly less common than 0 and 1, but how much less? I don't know, but we have to conclude that the true size of a bit is probably something more like 1.00000000000000001 bits rather than 1 bit.

Re: C++ proposal: There are exactly 8 bits in a byte

#166

Post by Isamu »

pjdesno wrote: post #15

During an internship in 1986 I wrote C code for a machine with 10-bit bytes, the BBN C/70. It was a horrible experience, and the existence of the machine in the first place was due to a cosmic accident of the negative kind.

I wrote code on a DECSYSTEM-20, the C compiler was not officially supported. It had a 36-bit word and a 7-bit byte. Yep, when you packed bytes into a word there were bits left over.

And I was tasked with reading a tape with binary data in 8-bit format. Hilarity ensued.

Re: C++ proposal: There are exactly 8 bits in a byte

#168

Post by jaysonvantuyl »

kstrauser wrote: post #157
tetron wrote: post #76

Earlier quoted context omitted.

There's only one right answer: Nybble - 4 bits Byte - 8 bits Snyack - 16 bits Lyunch - 32 bits Dynner - 64 bits

In the spirit of redefining the kilobyte, we should define byte as having a nice, metric 10 bits. An 8 bit thing is obviously a bibyte. Then power of 2 multiples of them can include kibibibytes, mebibibytes, gibibibytes, and so on for clarity.

ಠ_ಠ

Re: C++ proposal: There are exactly 8 bits in a byte

#169

Post by bastawhiz »

Nevermark wrote: post #128
harry8 wrote: post #25

Is C++ capable of deprecating or simplifying anything? Honest question, haven't followed closely. rand() is broken,I;m told unfixable and last I heard still wasn't deprecated. Is this proposal a test? "Can we even drop support for a solution to a problem literally nobody has?"

I think you are right. Absolutely. Don’t break perfection!! Just accumulate more perfection. What we need is a new C++ symbol that reliably references eight bit bytes, without breaking compatibility, or wasting annnnnny opportunity to expand the kitchen sink once again. I propose “unsigned byte8” and (2’s complement) “signed byte8”. And “byte8” with undefined sign behavior because we can always use some more spice. “…

> For the damn accountants who care about the cost of bytes.

Finally! A language that can calculate my S3 bill

Re: C++ proposal: There are exactly 8 bits in a byte

#170

Post by Spivak »

cogman10 wrote: post #109
spongebobstoes wrote: post #66

Earlier quoted context omitted.

One thought is that it's always a whole number of bits (3) to bit-address within a byte. It's 3.5 bits to bit address a 10 bit byte. Sorta just works out nicer in general to have powers of 2 when working on base 2.

This is basically the reason. Another part of it is the fact that it's a lot easier to represent stuff with hex if the bytes line up. I can represent "255" with "0xFF" which fits nice and neat in 1 byte. However, now if a byte is 10bits that hex no longer really works. You have 1024 values to represent. The max value would be 0x3FF which just looks funky. Coming up with an alphanumeric system to represent 2^10 cleanl…

We probably wouldn't have chosen hex in a theoretical world where bytes were 10 bits, right? It would probably be two groups of 5 like 02:21 == 85 (like an ip address) or five groups of two 0x01111 == 85. It just has to be one of its divisors.
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