The Field Catalog 
The field cataog is a table of type LVC_T_FCAT that contains information on the fields to be displayed. For example, the ALV uses this table to identify the type of a field.
You can use fields of this catalog to determine the number format and column properties of the list to be output.
Note
In certain exceptional cases it is not necessary to transfer the field catalog (see also: Generating the Field Catalog Automatically).
Structure
The field catalog contains more than 60 fields, some of which are only used internally. Those fields that are relevant to application developers are described in Fields of the Field Catalog.
Integration
Generally, you are recommended to fill the fields of the field catalog before the list is displayed for the first time and pass them in method set_table_for_first_display. To adjust a field catalog generated by the ALV to your special requirements before list output, you use function module LVC_FIELDCATALOG_MERGE.
Methods get_frontend_fieldcatalog and set_frontend_fieldcatalog allow you to change the field catalog after list output.
Note
Report BCALV_GRID_03 in development class SLIS uses this function module to hide columns before the list is displayed.