On 8 mar, 23:09, Ioannis Vranos <ivra...@nospam.no.spamfreemail.gr>

wrote:

Is there any mentioning in the standard of the number of bits

of the various built in types, apart from char/signed

char/unsigned char types? Or only about the minimum value

ranges of them?

No. But for integral types, the standard does impose a pure

binary representation, so the minimum value ranges do impose a

minimum number of bits. For floating point types, the standard

imposes minimum ranges and precision, which also imposes a

minimum amount of information present---if a "bit" is a binary

digit, this also imposes a certain minimum number of bits.

There's also a requirement that sizeof be an integral type, and

that you can examine all of the bits of an object (regardless of

its type) using unsigned char. Independently of the requirement

that CHAR_BIT be at least 8, this would forbid the usual PDP-10

organization of 36 bit words, with 5 7 bit bytes per word (and

one unused bit). It doesn't require that all bits participate

in the value representation, however---on a Unisys MCP, for

example, you can see all 48 bits of an int accessing it as an

array of [6] unsigned char, but only 40 participate in the value

representation, and only 39 can be accessed using unsigned int

with shift and masking operations.

--

James Kanze (GABI Software) email:ja*********@gmail.com

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