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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

#81

Post by knome »

donatj wrote: post #56

So please do excuse my ignorance, but is there a "logic" related reason other than hardware cost limitations ala "8 was cheaper than 10 for the same number of memory addresses" that bytes are 8 bits instead of 10? Genuinely curious, as a high-level dev of twenty years, I don't know why 8 was selected. To my naive eye, It seems like moving to 10 bits per byte would be both logical and make learning the trade just a li…

likely mostly as a concession to ASCII in the end. you used a typewriter to write into and receive terminal output from machines back in the day. terminals would use ASCII. there were machines with all sorts of smallest-addressable-sizes, but eight bit bytes align nicely with ASCII. makes strings easier. making strings easier makes programming easier. easier programming makes a machine more popular. once machines started standardizing on eight bit bytes, others followed. when they went to add more data, they kept the byte since code was written for bytes, and made their new registeres two bytes. then two of those. then two of those. so we're sitting at 64 bit registers on the backs of all that that came before.

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

#82

Post by bbkane »

hexo wrote: post #45

Why? Pls no. We've been told (in school!) that byte is byte. Its only sometimes 8bits long (ok, most of the time these days). Do not destroy the last bits of fun. Is network order little endian too?

I think there's plenty of fun left in the standard if they remove this :)

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

#83

Post by morio »

donatj wrote: post #56

So please do excuse my ignorance, but is there a "logic" related reason other than hardware cost limitations ala "8 was cheaper than 10 for the same number of memory addresses" that bytes are 8 bits instead of 10? Genuinely curious, as a high-level dev of twenty years, I don't know why 8 was selected. To my naive eye, It seems like moving to 10 bits per byte would be both logical and make learning the trade just a li…

One example from the software side: A common thing to do in data processing is to obtain bit offsets (compression, video decoding etc.). If a byte would be 10 bits you would need mod%10 operations everywhere which is slow and/or complex. In contrast mod%(2^N) is one logic processor instruction.

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

#84

Post by NL807 »

jsheard wrote: post #80
favorited wrote: post #53

Previously, in JF's "Can we acknowledge that every real computer works this way?" series: "Signed Integers are Two’s Complement" https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p09... >

Maybe specifying that floats are always IEEE floats should be next? Though that would obsolete this Linux kernel classic so maybe not. https://github.com/torvalds/linux/blob/master/include/math-e...

Love it

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

#85

Post by skissane »

forrestthewoods wrote: post #28
JamesStuff wrote: post #2

Not sure about that, seems pretty controversial to me. Are we forgetting about the UNIVACs?

Do UNIVACs care about modern C++ compilers? Do modern C++ compilers care about UNIVACs? Given that Wikipedia says UNIVAC was discontinued in 1986 I’m pretty sure the answer is no and no!

The UNIVAC 1108 (and descendants) mainframe architecture was not discontinued in 1986. The company that owned it (Sperry) merged with Burroughs in that year to form Unisys. The platform still exists, but now runs as a software emulator under x86-64. The OS is still maintained and had a new release just last year. Around the time of the merger the old school name “UNIVAC” was retired in a rebranding, but the platform survived.

Its OS, OS 2200, does have a C compiler. Not sure if there ever was a C++ compiler, if there once was it is no longer around. But that C compiler is not being kept up to date with the latest standards, it only officially supports C89/C90 - this is a deeply legacy system, most application software is written in COBOL and the OS itself itself is mainly written in assembler and a proprietary Pascal-like language called “PLUS”. They might add some features from newer standards if particularly valuable, but formal compliance with C99/C11/C17/C23/etc is not a goal.

The OS does contain components written in C++, most notably the HotSpot JVM. However, from what I understand, the JVM actually runs in x86-64 Linux processes on the host system, outside of the emulated mainframe environment, but the mainframe emulator is integrated with those Linux processes so they can access mainframe files/data/apps.

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

#86

Post by II2II »

dathinab wrote: post #19
JamesStuff wrote: post #2

Not sure about that, seems pretty controversial to me. Are we forgetting about the UNIVACs?

idk. by today most software already assumes 8 bit == byte in subtle ways all over the place to a point you kinda have to use a fully custom or at least fully self reviewed and patched stack of C libraries so delegating such by now very very edge cases to non standard C seems fine, i.e. seems to IMHO not change much at all in practice and C/C++ compilers are anyway full of non standard extensions and it's not that CHA…

> most software already assumes 8 bit == byte in subtle ways all over the place

Which is the real reason why 8-bits should be adopted as the standard byte size.

I didn't even realize that the byte was defined as anything other than 8-bits until recently. I have known, for decades, that there were non-8-bit character encodings (including ASCII) and word sizes were all over the map (including some where word size % 8 != 0). Enough thought about that last point should have helped me realize that there were machines where the byte was not 8-bits, yet the rarity of encountering such systems left me with the incorrect notion that a byte was defined as 8-bits.

Now if someone with enough background to figure it out doesn't figure it out, how can someone without that background figure it out? Someone who has only experienced systems with 8-bit bytes. Someone who has only read books that make the explicit assumption of 8-bit bytes (which virtually every book does). Anything they write has the potential of breaking on systems with a different byte size. The idea of writing portable code because the compiler itself is "standards compliant" breaks down. You probably should modify the standard to ensure the code remains portable by either forcing the compiler for non-8-bit systems to handle the exceptions, or simply admitting that compiler does not portable code for non-8-bit systems.

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

#87

Post by epcoa »

tbrownaw wrote: post #79
mathgenius wrote: post #26

Earlier quoted context omitted.

Ternary computers have 8 tits to a byte.

Should be either 9 or 27 I'd think.

Why can’t it be 8?, the fact that it’s a trit doesn’t put any constraint on the byte (tryte ? size). You could actually make it 5 or 6 trits (~9.5 bits) for similar information density. The Setun used 6 trit addressable units.

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

#88

Post by WalterBright »

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 programmed the Intel Intellivision cpu which had a 10 bit "decl". A wacky machine. It wasn't powerful enough for C.

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

#89

Post by Taniwha »

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've worked on a machine with 9-bit bytes (and 81-bit instructions) and others with 6-bit ones - nether has a C compiler

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

#90

Post by WalterBright »

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.

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