Is CHAR_BIT ever > 8?

Question

The ISO C Standard requires CHAR_BIT to be at least 8.

With POSIX mandating CHAR_BIT be equal to 8, and (almost?) all networking and communication standards using octets, is there any contemporary C implementation where CHAR_BIT > 8?

(Note: I'm not interested in historic computer architectures using 18 or 36 bit words. It's genuinely a question about C as it is used today on current hardware; think systems with a C99 or later implementation).

Related to http://stackoverflow.com/questions/2098149/what-platforms-have-something-other-than-8-bit-char — Klas Lindbäck, Aug 19 '15 at 09:58
the wide characters, used in several language alphabets is usually 16 bits — user3629249, Aug 20 '15 at 12:45
Yes. Old Cray machines had the equivalent of `CHAR_BIT == 32` (so `sizeof(int) == 1 == sizeof(short) == sizeof(char)`. Modern DSP systems can have `CHAR_BIT == 16`. — Jonathan Leffler, Jul 13 '16 at 07:03
The TI compiler for the TMS320C54x (commonly known as the C54x) defines `CHAR_BIT` as 16. See Table 7.1 in the User's Guide: http://www.ti.com.cn/cn/lit/ug/spru103g/spru103g.pdf — Michael Burr, Jul 13 '16 at 07:20
It would be interesting to see if there are non-DSP implementations where `CHAR_BIT > 8`. — a3f, Jul 13 '16 at 19:38
The XAP processor created by Cambridge Consultants and powering a few billion Bluetooth headsets around the world have CHAR_BIT == 16 — Chris St John, Jul 15 '16 at 16:29
@ChrisStJohn You should post an answer with a link to the official documentation specifying CHAR_BIT. — 2501, Jul 17 '16 at 08:04
Possibly also related to: [this SO post](http://stackoverflow.com/questions/19708810/fixed-char-bit-on-various-systems). — user3078414, Jul 18 '16 at 19:12
Also see [Exotic architectures the standards committees care about](https://stackoverflow.com/q/6971886/1708801) — Shafik Yaghmour, Jun 11 '17 at 06:51
Related: [Are there machines, where sizeof(char) != 1, or at least CHAR_BIT > 8?](https://stackoverflow.com/q/2215445/12149471) — Andreas Wenzel, Jun 01 '23 at 07:05

score 31 · Accepted Answer · edited Jul 13 '16 at 10:11

31

TMS320C28x DSP from Texas Instruments has a byte with 16 bits.

Documentation for the compiler specifies CHAR_BIT as 16 on page 101.

This appears to be a modern processor (currently being sold), compilers supporting C99 and C++03.

edited Jul 13 '16 at 10:11

Jens

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answered Jul 13 '16 at 07:29

2501

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Two outstanding answers making it hard to select a bounty winner. So I rolled a dice... one of you gets the "accept" score, the other the bounty. – Jens Jul 18 '16 at 21:21

score 26 · Answer 2 · answered Jul 13 '16 at 19:35

26

Another example is Analog Devices' SHARC processor family. Its C implementation, CrossCore Embedded Studio, has CHAR_BIT == 32 and claims to provide freestanding C99 and C++11 conformance.

answered Jul 13 '16 at 19:35

a3f

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Curious, is a `char` a signed char or an unsigned one there? – chux - Reinstate Monica Dec 14 '19 at 18:25
@chux-ReinstateMonica signed. Search for `"plain" char` in the document. – a3f Dec 15 '19 at 03:04
[Compiler Manual for SHARC Processors](http://www.analog.com/media/en/dsp-documentation/software-manuals/cces-SharcCompiler-manual.pdf) has "A "plain" char has the same range and value as a signed char." . Thanks. – chux - Reinstate Monica Dec 15 '19 at 03:33

score 8 · Answer 3 · answered Apr 22 '17 at 17:39

Analog Devices' SHARC DSP was already mentioned (CHAR_BIT==32). Let me add that recent SHARC+ cores (I use ADSP-SC589 and CCES toolchain) can run apps written in two modes: CHAR_BIT == 8 or CHAR_BIT == 32. You can even mix'n'match the two modes together in one app. Although I would not recommend this for development in general, I find it useful when porting code.

Is CHAR_BIT ever > 8?

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