Create Datum dialog box

You can create a datum from scratch or modify an existing datum and save it as a new one. To modify a predefined datum, you must assign it a new code before you can save it.

Code
Specifies a unique code for the datum.
Description

Specifies a description of the datum

Ellipsoid

Select the ellipsoid on which this datum will be based. To edit the ellipsoid you select, you must use the Create Ellipsoid dialog box or the Create Coordinate System Wizard.

Source
Enter the data source from which the values for this datum were taken.