C language-struct (struct) bit field (:) Detailed explanation

struct (struct) bit field (:) Detailed explanation

This address: http://blog.csdn.net/caroline_wendy/article/details/26722511

structures (structs) can use bit fields (:), saving space, for example, with the following code,

In struct A, the first variable x occupies 1 characters, y occupies 2 characters, and Z occupies 33 characters (out of bounds);

However, sizeof () will take the initiative to make up, such as X+y occupies a total of 4 bytes, Z occupies 8 bytes, so the structure occupies 12 bytes;

When the addition operation is used, it is initialized to 0;

Code:

/* * test.cpp * *  Created on:2014.05.23 *      author:spike *//*eclipse CDT, gcc 4.8.1*/#include <iostream> #inc Lude <stdio.h>using namespace std;struct a {int x:1;int y:2;int z:33;}; int main () {a d;cout << &d << std::endl;d.z = d.x + d.y;printf ("%d%d%d%d\n", D.x, D.y, d.z, sizeof (d)); r Eturn 0;}

Output:

0X22FED40 0 0 12

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C language-struct (struct) bit field (:) Explain in detail