# What are Variables?

Variables are named spaces in memory for storing data. You can think of a variable as a container for a value.

Create all the variables you need, and then associate variables with switches, lamps, data displays, and other objects on the screen.

To communicate with external devices connected to the display unit, create a variable and map a device address.

Variables can be categorized in two different ways according to their settings.

- Internal Variables and External variables: Not associated with or associated with device addresses.
- Local Variables and Global Variables: Cannot be used or can be used globally in the project.

Local variables can only be used as internal variables.

Global variables can be used as both internal and external variables.

## Internal Variables and External Variables

Internal variables are not associated with a device and are used only for internal display unit operations.

External variables are associated with a device address.

## Local Variables and Global Variables

Local variables are internal variables accessible within a screen, content, or its scripts where the local variable is set up. Local variables are listed in the corresponding screen or content.

Global variables are internal and external variables that are accessible throughout a project. Global variables are listed under [All Variables] in the [Project Explorer].

For information about conditions and behavior of local variables, refer to the following.

Local Variables