> For the complete documentation index, see [llms.txt](https://docs.os.uk/os-downloads/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.os.uk/os-downloads/products/addresses-and-names-portfolio/os-emergency-services-gazetteer/os-esg-technical-specification/code-lists.md).

# Code lists

A code list is a controlled set of allowable labels or codes represented as an alphanumeric attribute. The pages in this section show the code lists used within the OS Emergency Services Gazetteer (OS ESG). Some of the code lists only apply to attributes of the feature type and both structured data types, whereas others will only apply to attributes of either the feature type or one of the two structured data types.

## Index

The pages in this section display the code lists in alphabetical order, with one code list provided per page:

* [AddressbasePostalCode](/os-downloads/products/addresses-and-names-portfolio/os-emergency-services-gazetteer/os-esg-technical-specification/code-lists/addressbasepostalcode.md)
* [BLPUStateCode](/os-downloads/products/addresses-and-names-portfolio/os-emergency-services-gazetteer/os-esg-technical-specification/code-lists/blpustatecode.md)
* [ChangeTypeCode](/os-downloads/products/addresses-and-names-portfolio/os-emergency-services-gazetteer/os-esg-technical-specification/code-lists/changetypecode.md)
* [ClassificationCode](/os-downloads/products/addresses-and-names-portfolio/os-emergency-services-gazetteer/os-esg-technical-specification/code-lists/classificationcode.md)
* [CountryCode](/os-downloads/products/addresses-and-names-portfolio/os-emergency-services-gazetteer/os-esg-technical-specification/code-lists/countrycode.md)
* [FileTypeCode](/os-downloads/products/addresses-and-names-portfolio/os-emergency-services-gazetteer/os-esg-technical-specification/code-lists/filetypecode.md)
* [LanguageCode](/os-downloads/products/addresses-and-names-portfolio/os-emergency-services-gazetteer/os-esg-technical-specification/code-lists/languagecode.md)
* [LogicalStatusCode](/os-downloads/products/addresses-and-names-portfolio/os-emergency-services-gazetteer/os-esg-technical-specification/code-lists/logicalstatuscode.md)
* [OfficialFlagCode](/os-downloads/products/addresses-and-names-portfolio/os-emergency-services-gazetteer/os-esg-technical-specification/code-lists/officialflagcode.md)
* [RPCCode](/os-downloads/products/addresses-and-names-portfolio/os-emergency-services-gazetteer/os-esg-technical-specification/code-lists/rpccode.md)
* [USRNMatchIndicatorCode](/os-downloads/products/addresses-and-names-portfolio/os-emergency-services-gazetteer/os-esg-technical-specification/code-lists/usrnmatchindicatorcode.md)

{% hint style="info" %}
Please note, not all of the code lists listed will be populated within the OS ESG product.
{% endhint %}


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.os.uk/os-downloads/products/addresses-and-names-portfolio/os-emergency-services-gazetteer/os-esg-technical-specification/code-lists.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.