编写注释的第一步是确定注释的约定，例如您要注释的内容和注释的格式。如果您正在使用存在文档编译工具的语言进行编程，例如 Java 的 Javadoc，C ++的 Doxygen 或 Go！的 godoc，请遵循工具的约定。这些约定都不是完美的，但是这些工具可提供足够的好处来弥补这一缺点。如果在没有现有约定可遵循的环境中进行编程，请尝试从其他类似的语言或项目中采用这些约定；这将使其他开发人员更容易理解和遵守您的约定。
约定有两个目的。首先，它们确保一致性，这使得注释更易于阅读和理解。其次，它们有助于确保您实际编写评论。如果您不清楚要发表的评论以及发表评论的方式，那么很容易最终根本不发表评论。
大多数注释属于以下类别之一：
接口：在模块声明（例如类，数据结构，函数或方法）之前的注释块。注释描述模块的接口。对于一个类，注释描述了该类提供的整体抽象。对于方法或函数，注释描述其整体行为，其参数和返回值（如果有），其生成的任何副作用或异常，以及调用者在调用该方法之前必须满足的任何其他要求。
- 数据结构成员：数据结构中字段声明旁边的注释，例如类的实例变量或静态变量。
- 实现注释：方法或函数代码内部的注释，它描述代码在内部的工作方式。
- 跨模块注释：描述跨模块边界的依赖项的注释。
最重要的注释是前两个类别中的注释。每个类都应有一个接口注释，每个类变量应有一个注释，每个方法都应有一个接口注释。有时，变量或方法的声明是如此明显，以至于在注释中没有添加任何有用的东西（getter 和 setter 有时都属于此类），但这很少见。评论所有内容要比花精力担心是否需要评论要容易得多。实施注释通常是不必要的（请参阅下面的 13.6. 实现注释：什么以及为什么... ）。跨模块注释是最罕见的，而且编写起来很成问题，但是当需要它们时，它们就很重要。 13.7. 跨模块设计决策 将更详细地讨论它们。
The first step in writing comments is to decide on conventions for commenting, such as what you will comment and the format you will use for comments. If you are programming in a language for which there exists a document compilation tool, such as Javadoc for Java, Doxygen for C++, or godoc for Go!, follow the conventions of the tools. None of these conventions is perfect, but the tools provide enough benefits to make up for that. If you are programming in an environment where there are no existing conventions to follow, try to adopt the conventions from some other language or project that is similar; this will make it easier for other developers to understand and adhere to your conventions.
Conventions serve two purposes. First, they ensure consistency, which makes comments easier to read and understand. Second, they help to ensure that you actually write comments. If you don’t have a clear idea what you are going to comment and how, it’s easy to end up writing no comments at all.
Most comments fall into one of the following categories:
Interface: a comment block that immediately precedes the declaration of a module such as a class, data structure, function, or method. The comment describe’s the module’s interface. For a class, the comment describes the overall abstraction provided by the class. For a method or function, the comment describes its overall behavior, its arguments and return value, if any, any side effects or exceptions that it generates, and any other requirements the caller must satisfy before invoking the method.
Data structure member: a comment next to the declaration of a field in a data structure, such as an instance variable or static variable for a class.
Implementation comment: a comment inside the code of a method or function, which describes how the code works internally.
Cross-module comment: a comment describing dependencies that cross module boundaries.
The most important comments are those in the first two categories. Every class should have an interface comment, every class variable should have a comment, and every method should have an interface comment. Occasionally, the declaration for a variable or method is so obvious that there is nothing useful to add in a comment (getters and setters sometimes fall in this category), but this is rare; it is easier to comment everything rather than spend energy worrying about whether a comment is needed. Implementation comments are often unnecessary (see Section 13.6 below). Cross-module comments are the most rare of all and they are problematic to write, but when they are needed they are quite important; Section 13.7 discusses them in more detail.