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From: brnstnd@kramden.acf.nyu.edu (Dan Bernstein)
Newsgroups: comp.lang.c
Subject: Re: Hexadecimal/octal constants
Message-ID: <1478:Mar2021:59:4991@kramden.acf.nyu.edu>
Date: 20 Mar 91 21:59:49 GMT
References: <RJOHNSON.91Mar20091144@olorin.shell.com>
Organization: IR
Lines: 26

In article <RJOHNSON.91Mar20091144@olorin.shell.com> rjohnson@shell.com (Roy Johnson) writes:
> Is it true on every platform that 0xf == 15?

Yes.

> Is it also true on every platform that for bitwise operations, C
> behaves as if it is on a two's complement machine, so that, e.g., the
> result of 0xf & 0x2 is 0x2,

Yes, the result of 0xf & 0x2 is 0x2. No, C does not ``behave as if it is
on a two's complement machine'' for bitwise operations: two's complement
has to do with the representation of negatives, and the bit operators
basically treat everything as unsigned. (Apparently ANSI implies that
any implementation must be one's-complement or two's-complement, but
this is beside the point.)

C does behave as if it is on a binary machine when it is working with
binary digits, even if it is on a base-10 machine or whatever else.

> even if the machine representation of
> 0xf is 1010 and 0x2 is 0101 [think hypothetical here 8^)]?

BEEP! :-) The machine representation is irrelevant. ``If the machine
represents 2 as 0101 and 5 as 1010, does 2 + 2 equal 5?''

---Dan