C - Basics Program输出是什么？ [英] C - Basics Program what is the output?

问题描述

What is the size of  the following structure?
typedef  struct
{
   int ctrl1;
   char flag;
   char flag2;
   int ctrl2;
   int ctrl3;
} MYREG;


a)14
b)20
c)24
d)16

推荐答案

取决于许多因素，主要是您使用的编译器。

如果使用旧的16位编译器，则int为2个字节。

如果使用更现代的编译器，则int可以是4或8个字节（我还没有看到使用128位整数的C编译器）。



另外，它将取决于你的编译器选项 - 有些将默认打包结构，其他人不会。如果它们打包它，它可能取决于目标处理器和编译器效率 - 一些组合将两个字符压缩为连续的字节，并且接下来的两个字节中的下一个int，其他将要求每个int以4字节开始边界。



所以，编译它，并尝试它。你为你的配置想出一个明确的答案并不困难。

Depends on a number of factors, primarily which compiler you use.
If you use an old 16 bit compiler, then an int is 2 bytes.
If you use a more modern compiler, then an int can be 4 or 8 bytes (I''ve yet to see a C compiler that used 128 bit integers).

In addition, it will depend on your compiler options - some will "pack" the structure by default, others won''t. If they do pack it, it may depend on the target processor and the compiler efficiency - some combinations will compact the two characters to successive bytes, and the following int into the next two bytes, others will require each int to start on a 4 byte boundary.

So, Compile it, and try it. It isn''t difficult for you to come up with a definitive answer for your configuration.

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