A constant is a fixed piece of data that exists only on the diagram. Use a constant instead of a control when you know that a certain piece of data should always be the same regardless of other parts of your code.
You can use the following types of constants in graphical programming:
Universal constant—Represents commonly used values that are always the same, such as pi (π), the speed of light, or the character that represents pressing the Enter key.
User-defined constant—Accepts user input. You define the values as you develop the code.