> For the complete documentation index, see [llms.txt](https://docs.b2ihealthcare.com/snowray/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.b2ihealthcare.com/snowray/reference/resources/codesystems.md).
# Code Systems
Code Systems contain all the relevant concepts that can be utilized to create [Value Sets](/snowray/reference/resources/valuesets.md).
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Can't find a resource? Visit the Resources [Features ](/snowray/reference/resources.md#features)section to find out more.
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Besides supporting national and international [Terminology Standards](/snowray/reference/resources/codesystems/terminology-standards.md), such as SNOMED CT, ICD-10, or LOINC, Snowray also supports the creation and maintenance of [Custom Code Systems](/snowray/reference/resources/codesystems/custom-code-systems.md).
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Below you can read about the features that apply to all Code Systems, while visiting a Code System subpage will reveal functionalities that are specific to the selected Code System.
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## Browsing
Users have the option to access Code Systems either from the [Dashboard](/snowray/reference/dashboard.md) or the [Resources Page](/snowray/reference/resources.md#resources-page). When starting out from the Dashboard, clicking the resource card will automatically take users to the ***Overview*** tab of the Code System. In case of approaching from the Resources page, pressing the resource title will result in the same, while double-clicking the row will open the ***Content*** tab. Once on the ***Content*** tab, users have access to the Code System hierarchy and browsing of the terminology itself can immediately begin.
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You can browse different versions of a Code System, if you click on the version tag indicated in the top-right corner of the resource's page and select an earlier version from the dropdown.
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## Searching
Clicking the small triangles next to the parent concepts enables users to search for [concepts](#concepts) by expanding the tree. Besides this aforementioned manual approach, another option offers to use the filter search for lexical matches.
Search results can be examined in a list or a tree view.
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By default, matching results are displayed in a flat list.
To switch between the views, click on the icon, and select the corresponding option from the menu.
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In addition to the filter search, Snowray also provides an advanced search option for certain Code Systems ([SNOMED CT](/snowray/reference/resources/codesystems/terminology-standards/snomed-ct/search.md) and Custom Code Systems).
## Concepts
When browsing a Code System, selecting a [concept](#concepts) navigates users to the concept details. On the concept's ***Overview*** tab descriptions, properties, and metadata are revealed. Some of the content is displayed in blue color, which indicates that it is a link to another concept. Clicking on those links navigates users to the linked concept's detailed overview.
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Concepts are read-only components and can be browsed only within a Code System.
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The concept's ***History*** tab displays the changes made to the selected [concept](#concepts). Each change is represented on a timeline and has an individual node. In their title, the nodes display the name of the user who did the modification and the elapsed time since the change, while the action that modified the concept can be found in the details part.
## Quick Link
Snowray's quick link feature enables users to take a look at specific concepts of a Code System without interrupting their browsing or searching flow.
When hovering over concepts in the terminology tree, the icon representing the *Open in new tab* option will appear.
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If you press , you will be taken to a new browser tab with the selected concept opened in the given Code System's ***Content*** tab.
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## Language selector
The icon displayed in the terminology tree header enables changing the display language in case of terminologies with multiple translations.
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The icon is displayed only when language selection is applicable to a given terminology.
Currently, the feature is supported for SNOMED CT National Extensions and the Unified Medical Language System (UMLS).
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To see the available languages, click on the icon. The alternatives will be displayed in a dropdown.
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SNOMED CT Canada Extension with French language selected
Switching to a translation will change the terminology content to be displayed in the selected language within the terminology tree.
Additionally, when selected in the hierarchy, concepts will be displayed in the preferred language in the concept ***Overview*** tab header as well.
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When selecting a translation other than the default language, the icon will turn blue, indicating that you are browsing content in another language.
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If a translation is not available for a given term, it will be displayed in the default language.
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The language selector is accessible from the terminology tree, therefore, users can also change the display language of the terminology tree content when referenced in other resources, i.e. when serving as domains for Value Sets and Concept Maps.
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