What's the value of characters in execution character set?

Question

Quote from C++03 2.2 Character sets:

"The basic execution character set and the basic execution wide-character set shall each contain all the members of the basic source character set..The values of the members of the execution character sets are implementation-defined, and any additional members are locale-specific."

According to this, 'A', which belongs to the execution character set, its value is implementation-defined. So it's not 65(ASCII code of 'A' in decimal), what?!

// Not always 65?
printf ("%d", 'A');

Or I've a misunderstanding as to the value of a character in execution character set?

Answer 1

Of course it can be ASCII's 65, if the execution character set is ASCII or a superset (such as UTF-8).

It doesn't say "it can't be ASCII", it says that it is something called "the execution character set".

Answer 2

So, the standard allows that the "execution character set" is other things than ASCII or ASCII derivatives. One example would be the EBCDIC character set that IBM used for a long time (there's probably still machines about using EBCDIC, but I suspect anything built in the last 10-15 years wouldn't be using that). The encoding of characters in EBCDIC is completely different from ASCII.

So, expecting, in code, that the value of 'A' is any particular value is not portable. There are also a whole heap of other "common assumptions" that will fail - that there are no "holes" between A-Z, and that 'A'-'a' == 32 are both false in EBCDIC. At least the characters A-Z are in the correct order! ;)