APIs and code documentation in DITA XML are linked using specific elements and techniques to ensure that developers can easily access and understand how to use APIs and related code. This linkage is essential for providing comprehensive and structured documentation for software development. Here’s how APIs and code documentation are linked in DITA XML:

1. API Documentation: APIs are documented using DITA elements like <reference> and <codeblock>. The <reference> element provides information about the API, its purpose, parameters, and usage. It can include details on the API’s functions, methods, and classes. Code examples can be included using the <codeblock> element to illustrate how to use the API in practice. These code examples are often syntax-highlighted for clarity.

2. Linking to Code Documentation: DITA XML allows you to create links between API documentation and code documentation. You can use the <xref> element to link from API descriptions to code examples, and vice versa. For instance, within the API documentation, you can provide links to relevant code samples that demonstrate how to implement the API. In code documentation, you can link back to the API reference, providing developers with a seamless transition between understanding the API and applying it in their code.

3. Code Versioning: Managing versions of code documentation is vital. In DITA XML, versioning can be handled using conditional processing attributes such as @product, @audience, or @platform. This allows you to provide code documentation for different versions of your software or for specific user groups. Developers can then access the version of code documentation that matches their needs or the version of the API they are using.

<!-- Example of linking API documentation to code documentation in DITA XML -->
<reference id="api-reference">
  <title>The API Title</title>
  <shortdesc>Brief description of the API.</shortdesc>
  <xref href="code-sample.dita" scope="external">See example code</xref>
</reference>

<!-- Example of code documentation linked to the API reference -->
<codeblock id="code-sample">
  <title>Code Example</title>
  <codeph><ph conref="api-reference.dita"/></codeph>
  <text><![CDATA[
    // Your code example here
  ]]></text>
</codeblock>

By implementing these techniques, DITA XML ensures that API documentation and code documentation are effectively linked, providing developers with the resources they need to work with your APIs and write code that interacts with them.