C++ FAQ Celebrating Twenty-One Years of the C++ FAQ!!!
(Click here for a personal note from Marshall Cline.)
Section 26:
26.1 Can sizeof(char) be 2 on some machines? For example, what about double-byte characters?
26.2 What are the units of sizeof?
26.3 Whoa, but what about machines or compilers that support multibyte characters. Are you saying that a "character" and a char might be different?!?
26.4 But, but, but what about machines where a char has more than 8 bits? Surely you're not saying a C++ byte might have more than 8 bits, are you?!?
26.5 Okay, I could imagine a machine with 9-bit bytes. But surely not 16-bit bytes or 32-bit bytes, right?
26.6 I'm sooooo confused. Would you please go over the rules about bytes, chars, and characters one more time?
26.7 What is a "POD type"?
26.8 When initializing non-static data members of built-in / intrinsic / primitive types, should I use the "initialization list" or assignment?
26.9 When initializing static data members of built-in / intrinsic / primitive types, should I worry about the "static initialization order fiasco"?
26.10 Can I define an operator overload that works with built-in / intrinsic / primitive types?
26.11 When I delete an array of some built-in / intrinsic / primitive type, why can't I just say delete a instead of delete[] a?
26.12 How can I tell if an integer is a power of two without looping?
26.13 What should be returned from a function?
[26.2] What are the units of sizeof?

Bytes.

For example, if sizeof(Fred) is 8, the distance between two Fred objects in an array of Freds will be exactly 8 bytes.

As another example, this means sizeof(char) is one byte. That's right: one byte. One, one, one, exactly one byte, always one byte. Never two bytes. No exceptions.