Microsoft如何说WinAPI中单词的大小为16位? [英] How can Microsoft say the size of a word in WinAPI is 16 bits?

问题描述

我刚刚开始学习WinAPI.在MSDN中，对WORD数据类型提供了以下说明.

I've just started learning the WinAPI. In the MSDN, the following explanation is provided for the WORD data type.

WORD
一个16位无符号整数.范围是0到65535(十进制).
此类型在WinDef.h中声明如下:
typedef unsigned short WORD;

WORD
A 16-bit unsigned integer. The range is 0 through 65535 decimal.
This type is declared in WinDef.h as follows:
typedef unsigned short WORD;

足够简单，并且它与我一直在学习中使用的其他资源相匹配，但是怎么可以确定地说它是16位呢? Wikipedia上的 C数据类型页指定

Simple enough, and it matches with the other resources I've been using for learning, but how can it can definitively said that it is 16 bits? The C data types page on Wikipedia specifies

short/short int/有符号的short/有符号的short int
短符号整数 类型.
能够至少包含[−32767，+32767]范围；因此， 它的大小至少为 16位.

short / short int / signed short / signed short int
Short signed integer type.
Capable of containing at least the [−32767, +32767] range; thus, it is at least 16 bits in size.

因此，根据C标准，short的大小可能为32位.但是谁决定要使用什么位大小呢?我找到了实用说明在这里.具体来说，该行:

So the size of a short could very well be 32 bits according to the C Standard. But who decides what bit sizes are going to be used anyway? I found a practical explanation here. Specifically, the line:

...这取决于两个处理器(更具体地说，是ISA，指令 设置架构，例如x86和x86-64)和编译器，包括 编程模型.

...it depends on both processors (more specifically, ISA, instruction set architecture, e.g., x86 and x86-64) and compilers including programming model.

那么这就是ISA，我想这是有道理的.这是我迷路的地方.看一下Wikipedia上的 Windows页面，我在侧栏中看到了这一点:

So it's the ISA then, which makes sense I suppose. This is where I get lost. Taking a look at the Windows page on Wikipedia, I see this in the side bar:

平台 ARM，IA-32，Itanium，x86-64，DEC Alpha，MIPS，PowerPC

Platforms ARM, IA-32, Itanium, x86-64, DEC Alpha, MIPS, PowerPC

我真的不知道这些是什么，但是我认为这些是处理器，每个处理器都有一个ISA.也许Windows支持这些平台，因为它们都保证对unsigned short使用16位吗?这听起来不太正确，但是我对这方面的知识还不够了解，无法进一步研究.

I don't really know what these are but I think these are processors, each which would have an ISA. Maybe Windows supports these platforms because all of them are guaranteed to use 16 bits for an unsigned short? This doesn't sound quite right, but I don't really know enough about this stuff to research any further.

回到我的问题:当C标准本身不保证short始终为16位时，Windows API如何能够typedef unsigned short WORD;然后说WORD是16位无符号整数?

Back to my question: How is it that the Windows API can typedef unsigned short WORD; and then say WORD is a 16-bit unsigned integer when the C Standard itself does not guarantee that a short is always 16 bits?

推荐答案

简单地说，WORD始终为16位.

Simply put, a WORD is always 16 bits.

由于WORD始终为16位，但unsigned short并非为16位，因此WORD并不总是unsigned short.

As a WORD is always 16 bits, but an unsigned short is not, a WORD is not always an unsigned short.

对于Windows SDK支持的每个平台，Windows头文件均包含#ifdef样式宏，这些宏可以检测编译器及其平台，并将Windows SDK定义的类型(WORD，DWORD等)关联到适当大小的平台类型.

For every platform that the Windows SDK supports, the windows header file contains #ifdef style macros that can detect the compiler and its platform, and associate the Windows SDK defined types (WORD, DWORD, etc) to the appropriately sized platform types.

这就是为什么Windows SDK实际上使用内部定义的类型(例如WORD)而不是使用语言类型:以便它们可以确保其定义始终正确的原因.

This is WHY the Windows SDK actually uses internally defined types, such as WORD, rather than using language types: so that they can ensure that their definitions are always correct.

Microsoft工具链附带的Windows SDK可能很懒，因为Microsoft c ++工具链始终使用16位无符号短裤.

The Windows SDK that ships with Microsoft toolchains, is possibly lazy, as Microsoft c++ toolchains always use 16bit unsigned shorts.

我不希望将Visual Studio C ++附带的windows.h放入GCC，clang等中，因为许多细节，包括使用Platform SDK分发的.iib文件导入dll的机制，都无法正常工作. Microsoft特定的实现.

I would not expect the windows.h that ships with Visual Studio C++ to work correctly if dropped into GCC, clang etc. as so many details, including the mechanism of importing dll's using .iib files that the Platform SDK distribute, is a Microsoft specific implementation.

另一种解释是:

Microsoft说WORD是16位.如果某人"想要调用Windows API，则他们必须传递一个16位值，其中API将字段定义为WORD. 微软还可能说，为了使用其Windows SDK中存在的Windows头文件来构建有效的Windows程序，用户必须选择具有16位short的编译器.

Microsoft says a WORD is 16 bits. If "someone" wants to call a windows API, they must pass a 16 bit value where the API defines the field as a WORD. Microsoft also possibly says, in order to build a valid windows program, using the windows header files present in their Windows SDK, the user MUST choose a compiler that has a 16bit short.

c ++规范没有说编译器必须将short s实现为16位-微软表示您选择构建Windows可执行文件的编译器必须.

The c++ spec does not say that compilers must implement shorts as 16 bits - Microsoft says the compiler you choose to build windows executables must.

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