> For the complete documentation index, see [llms.txt](https://docs.videc.de/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.videc.de/acron-9.3/en/anlagenkonfiguration/prozessanbindung/provider/providerid/variablengruppe/extvar-id.md).

# External variable

### Identification

Make sure the name is unique, so as to ensure proper identification of the variable.

Note

The identifier of the external variable must conform to the syntax rules of the communication driver. For more information on the syntax of external variables refer to the Help of the current selected interface driver.

If the identification contains special characters, they are replaced by '\_' during automatic generation of process variables in their identification.

When using the " symbol, this external variable cannot be used for process data linkage of the process variables.

{% hint style="info" %}
Attention - DATA LOSS

If the variable's identifier is changed, all existing data are updated. This means any assignments will be lost if data from a plant backup are re-imported into the plant later. This relates to all data relating to the variable(s), such as comments, auto variables and reports.
{% endhint %}

### Name

The name of the variable helps to provide a clear overview in configuration; it is not a mandatory field.

### Description:

The description offers the facility to enter additional information on the external variable. This serves primarily as an aid to the project designer in enhancing user-friendliness when configuring the plant.

For some providers additional information is stored in this field by default, e.g. WinCC:

*Floating-point number 32-bit IEEE 754* or *Text tag 8-bit character set*


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