Is there an actual 4-bit integer data type in C++11

Question

I require a 4 bit integer in a design for less memory use. In any version of c++ ,c++11 ,c++14 any can be used for the design.

No there isn't such type. But you can always use `uint8_t` and bit masking and shifting. — πάντα ῥεῖ, Jun 12 '17 at 07:07
The smallest integer type in C++ is `char` which is usually 8 bits. Are you targeting a memory-constrained embedded system? Otherwise it's more work to try these kind of micro-optimizations (it will also make the code harder to read, understand and maintain). It might also be a bit of premature optimization. Please try to elaborate on *why* you want to use "less memory" in a way that will probably use more CPU cycles instead. — Some programmer dude, Jun 12 '17 at 07:08
If you are genuinely interested in this topic, check out: CppCon 2016: Chandler Carruth “High Performance Code 201: Hybrid Data Structures" — keith, Jun 12 '17 at 08:06

score 7 · Answer 1 · answered Jun 12 '17 at 07:07

7

There is no native 4bit datatype. But you could use an 8bit one to hold two 4bit values in the high/low nibble.

answered Jun 12 '17 at 07:07

Jesper Juhl

nibble is also used only in the struct. Is there any direct way to use the 4 bit int – Aman Gupta Jun 12 '17 at 07:25
3

@AmanGupta _" Is there any direct way to use the 4 bit int"_ No. – πάντα ῥεῖ Jun 12 '17 at 07:43

score 4 · Answer 2 · answered Jun 12 '17 at 07:08

4

no, but you can use:

struct A {
   unsigned int value1 : 4;
   unsigned int value2 : 4;
};

answered Jun 12 '17 at 07:08

kain64b

1

But the struct also use memory space ,so how much the total space is used in this case. – Aman Gupta Jun 12 '17 at 07:13
2

@emlai That's unfortunately [not true](http://coliru.stacked-crooked.com/a/a5037c96e3494cf8). – πάντα ῥεῖ Jun 12 '17 at 07:20
3

It would be true if you used `uint8_t` or `char` instead (assuming 8-bit char) – krzaq Jun 12 '17 at 07:21
Note that `sizeof(char)` always returns 1, so nothing can be smaller than a char - even is char is not 8 bits wide. – Richard Critten Jun 12 '17 at 07:34

2 Answers2