Range of values in C Int and Long 32 - 64 bits

Question

I'm confused with range of values of Int variable in C.

I know that a 32bits unsigned int have a range of: 0 to 65,535. So long has 0 to 4,294,967,295

This is fine in 32bits machine. But now in 64bits machines all thing keep the same? Or maybe my int capacity is different?

I understand this questions as newbie, but I'm really confused. This method signature is not helping too. :)

unsigned long long int atomicAdd(unsigned long long int* address, unsigned long long int val); 

Answer 1

In C and C++ you have these least requirements (i.e actual implementations can have larger magnitudes)

signed char: -2^07+1 to +2^07-1 short:       -2^15+1 to +2^15-1 int:         -2^15+1 to +2^15-1 long:        -2^31+1 to +2^31-1 long long:   -2^63+1 to +2^63-1 

Now, on particular implementations, you have a variety of bit ranges. The wikipedia article describes this nicely.

Answer 2

No, int in C is not defined to be 32 bits. int and long are not defined to be any specific size at all. The only thing the language guarantees is that sizeof(char)<=sizeof(short)<=sizeof(long).

Theoretically a compiler could make short, char, and long all the same number of bits. I know of some that actually did that for all those types save char.

This is why C now defines types like uint16_t and uint32_t. If you need a specific size, you are supposed to use one of those.