# Parameters

Although not mandatory it is common for an operation mode to have parameters.

{% hint style="info" %}
Operation mode parameters are defined as FileGlobal variables in TestStand.
{% endhint %}

![Operation Mode Parameter](/files/81zZeEcn3wsJje27hxWl)

The `FileGlobals.LTT.OM` structure is an array of containers. Each container represents the parameters for a single operation mode sequence. **The container must be named exactly like the operation mode sequence itself**. Within each operation mode parameter container you can add as many variables as needed. **Only variables of type *****string*****, *****bool***** and *****numeric***** are supported**.

For each operation mode parameter variable you set a **name**, a **default value** and a **description** (as variable comment). When the testplan is loaded in GUI you can see a list of all operation modes with their parameters in [F10 dialog](/ltt/documentation/ltt-gui-manual/lttgui/dialogs/f10testparameterconfiguration.md). There you can modify individual parameters, even during the testplan is running. The default parameter values entered in TestStand remain untouched. If you run without GUI you work with the default parameters. You need to change the values in TestStand if they do not fit your current need.

![Operation Mode Parameter Compare](/files/aGfdZloMMEJp0bZidSSS)


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