“关键字"与“关键字"之间有什么区别和“保留字"? [英] What is the difference between "keyword" and "reserved word"?

问题描述

关键字和保留字有什么区别?

例如，在建议书中在C ++中可以读取以下语句:

For example, in the proposal for concepts in C++ one can read the following statement:

该提案引入了五个新的关键字:概念，概念图，位置，公理和延迟检查.所有这些关键字也将是 保留字.

This proposal introduces five new keywords: concept, concept map, where, axiom, and late check. All of these keywords will also be reserved words.

推荐答案

关键字在一种语言中具有特殊含义，并且是语法的一部分.

Keywords have a special meaning in a language, and are part of the syntax.

保留的单词是不能被用作标识符(变量，函数等)的单词，因为它们是语言所保留的.

Reserved words are words that cannot be used as identifiers (variables, functions, etc.), because they are reserved by the language.

实际上，大多数关键字都是保留字，反之亦然.但是，由于它们是两种不同的情况，因此可能会发生以下情况:关键字不是保留字(例如，关键字仅在特殊上下文中才有意义，因此可以用作标识符)，或者保留字不是关键字(例如，因为它是保留供将来使用的.)

In practice most keywords are reserved words and vice versa. But because they're two different things it may happen that a keyword is not a reserved word (e.g. a keyword only has meaning in a special context, and can therefore be used as an identifier), or a reserved word is not a keyword (e.g. because it is reserved for future use).

更新:其他示例给出的一些例子说明了区别:

Update: Some examples as given by others that illustrate the distinction:

• 在Java中，goto是保留字，但不是关键字(因此，您完全不能使用它)
• Fortran没有没有保留字，所有关键字(如果有，那么等等)都可以用作标识符

• In Java, goto is a reserved word but not a keyword (as a consequence, you cannot use it at all)
• Fortran has no reserved words, all keywords (if, then, etc.) can be used as identifiers

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