signed

Is enum type signed or unsigned? Is the Signedness of enums differ in C/C99/ANSI C/C++/C++x/GNU C/ GNU C99? Thanks An enum is guaranteed to be represented by an integer, but the actual type (and its signedness) is implementation-dependent. You can force an enumeration to be represented by a signed type by giving one of the enumerators a negative value: enum SignedEnum { a = -1 }; In C++0x, the underlying type of an enumeration can be explicitly specified: enum ShortEnum : short { a }; (C++0x also adds support for scoped enumerations) For completeness, I'll add that in The C Programming

Let's say I have this number i = -6884376 . How do I refer to it as to an unsigned variable? Something like (unsigned long)i in C. Assuming : You have 2's-complement representations in mind; and, By (unsigned long) you mean unsigned 32-bit integer, then you just need to add 2**32 (or 1 << 32) to the negative value. For example, apply this to -1: >>> -1 -1 >>> _ + 2**32 4294967295L >>> bin(_) '0b11111111111111111111111111111111' Assumption #1 means you want -1 to be viewed as a solid string of 1 bits, and assumption #2 means you want 32 of them. Nobody but you can say what your hidden

I have a function that I would like to be able to return special values for failure and uninitialized (it returns a pointer on success). Currently it returns NULL for failure, and -1 for uninitialized, and this seems to work... but I could be cheating the system. IIRC, addresses are always positive, are they not? (although since the compiler is allowing me to set an address to -1, this seems strange). [update] Another idea I had (in the event that -1 was risky) is to malloc a char @ the global scope, and use that address as a sentinel. No, addresses aren't always positive - on x86_64, pointers

Does C treat hexadecimal constants (e.g. 0x23FE) and signed or unsigned int? The number itself is always interpreted as a non-negative number. Hexadecimal constants don't have a sign or any inherent way to express a negative number. The type of the constant is the first one of these which can represent their value: int unsigned int long int unsigned long int long long int unsigned long long int It treats them as int literals(basically, as signed int!). To write an unsigned literal just add u at the end: 0x23FEu According to cppreference , the type of the hexadecimal literal is the first type