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#Typesy iso code

In that case, the C++ compiler would need to addĮxtra instructions when compiling code using char* pointers. The 36-bit word, the second could be a bit-offset within that word. Another validĪpproach would be to define a “byte” as 9 bits, and simulate a char* by two words of memory: the first could point to One way to abide by all the above rules is for a PDP-10 C++ compiler to define a “byte” as 36 bits. Possible for a pointer to point 8 bits to the right of where some other pointer points. That means a pointer can point only at things on a 36-bit boundary: it is not The PDP-10 has 36-bit words with no hardware facility to addressĪnything within one of those words. Let’s work an example to illustrate these rules. Include the header, then the actual number of bits per byte will be given by the CHAR_BIT macro.

The C++ language gives you a way to find out how many bits are in a byte in your particular implementation:.

Will never cause a change to a different byte.

The C++ language guarantees there are no bits that are part of two distinct bytes.

If you grind your way through memory via a char*, you will be able to see every bit. This means every bit in memory is part of aīyte.

The C++ language guarantees there are no bits between two bytes.

The C++ language guarantees that a char* ( char pointers) can address individual bytes.

Each of these things that the C++ language calls a byte has at least 8 bits, but might have more than 8 bits.

The C++ language gives the programmer the impression that memory is laid out as a sequence of something C++ calls.

Would you please go over the rules about bytes, chars, and characters one more time? As in 8 times 8.Īnd yes, you’re right, combining with the above would mean that a char on that implementation would

I have heard of one implementation of C++ that has 64-bit “bytes.” You read that right: a byte on that But surely not 16-bit bytes or 32-bit bytes, right?

Okay, I could imagine a machine with 9-bit bytes. But there are implementations of C++ that The C++ language guarantees a byte must always have at least 8 bits. Yep, that’s right: a C++ byte might have more than 8 bits. 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?!? Take a deep breathĪnd repeat after me: “character and char might be different.” There, doesn’t that feel better? No? Well keep reading I’m really sorry if that hurts, but believe me, it’s better to get all the pain over with at once. Yes that’s right: the thing commonly referred to as a “character” might be different from the thing C++ calls a Are you saying that a “character” and a char might be different?!? Whoa, but what about machines or compilers that support multibyte characters. One, one, one,Įxactly one byte, always one byte. What are the units of sizeof?įor example, if sizeof(Fred) is 8, the distance between two Fred objects in an array of Freds will be exactly 8Īs another example, this means sizeof(char) is one byte. The pain will go away by sometime next week. Look, I know this is going to hurt your head, so please, please just read the next few FAQs in sequence and hopefully Never, never, never.Įven if you think of a “character” as a multi-byte thingy, char is not. Built-in / Intrinsic / Primitive Data Types Can sizeof(char) be 2 on some machines? For example, what about double-byte characters?