You must already have created the internal data types in the class to which you want to refer when you create the attributes. For further information, refer to Creating Internal Types in Classes.

1. Start the Class Editor in change mode.
2. Choose Attributes.
3. To create an attribute, enter the following:
   
   - Attribute
   A unique name that identifies the attribute. Remember to observe the naming conventions in ABAP Objects.
   
   - Type
   You can specify an attribute as a constant, an instance attribute, or a static attribute (that is shared by all instances of the class).
   
   - Visibility
   Defines the visibility of attributes to users of the class. If an attribute is public, it is assigned to the public section of the class and can be addressed by any user. Remember that public attributes form part of the external point of contact to the class, and as such stand in the way of full encapsulation.
   Protected attributes are visible in and can be addressed by all subclasses of the class.
   Private attributes are only visible in and can only be addressed by the defining class. In particular, they are not visible in the subclasses of the class.
   
   - Modeled
   If this option is set, the system does not enter the component in the class pool and the component cannot be addressed at runtime.
   
   - Read Only
   If this option is set, users cannot change this attribute.
   
   - Typing method
   ABAP keyword to specify the type reference. You can use TYPE, LIKE or
   Type Ref To (for class references).
   
   - Reference type
   This may be any elementary ABAP type (including generic types) or an object type (classes and interfaces).
   
   - Description
   Short description of the component
   
   - Initial value
   If the attribute is a constant, you must specify an initial value.
   
4. Repeat steps 1 to 3 for each attribute.
   
   Example:
   
   
5. Save your entries.