像_NAME符号的含义，__NAME，_NAME_，__name__ [英] Meaning of notations like _NAME, __NAME, _NAME_, __NAME__
问题描述
我在无数的C / C ++头文件和源文件看到了这一点。结果
除了个人preference，什么是这些不同的符号的含义？
I've seen this in countless C/C++ header and source files.
Apart from personal preference, what's the meaning of each of these different notations?
-
_NAME -
__名称 -
_NAME _ -
__ __名称 -
NAME_t
_NAME__NAME_NAME___NAME__NAME_t
坦率地说，我唯一COM prehend是 _NAME ，这是一个类（至少在C＃这是）的私有成员。
Quite honestly, the only one I comprehend is _NAME, which is a private member of a class (at least in C# it is).
有人能解释其中的区别呢？结果
并且，如果有任何其他明显的记号作为这样，请提及它们（甚至在其他类似的语言）。
Can someone explain the difference among them?
And if there are any other noticeable notations as such, please mention them (even in other similar languages).
谢谢！
推荐答案
与开头的名称_ 或 __ 通常是保留的标识符，你不应该定义/创建与该公约开头的标识符。 （_用大写以下）
Names that begin with _ or __ are typically for reserved identifiers, and you should not define/create identifiers that begin with that convention. (_ with Upper Case following)
从C99标准7.1.3 - 保留标识符
From C99 standard, 7.1.3 - "Reserved Identifiers"
- 所有鉴定连接器与下划线和大写字母或其他开头
下划线，始终保留用于任何用途。
— All identifiers that begin with an underscore and either an uppercase letter or another underscore are always reserved for any use.
- 所有鉴定连接器以下划线开头总是保留用作鉴定连接器
在这两个普通和标记的名称空间连接的文件范围。
— All identifiers that begin with an underscore are always reserved for use as identifiers with file scope in both the ordinary and tag name spaces.
从C ++ 03标准（修订C ++ 98），一节17.4.3.1.2 - 全局名称
From C++03 Standard (amendment to C++98), section 17.4.3.1.2 - "Global Names"
- 包含一个双下划线（_ _）或以下划线后跟一个大写开头的每个名称
字母（2.11）是保留用于任何用途的实现。
— Each name that contains a double underscore (_ _) or begins with an underscore followed by an upper- case letter (2.11) is reserved to the implementation for any use.
- 每个以下划线开头的名称被保留到实现用作该名称
全局命名空间
— Each name that begins with an underscore is reserved to the implementation for use as a name in the global namespace
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