cd18d7a2_logue_Format___Stellarium_Wiki_Star_Data_Record_Type_0_Description
[Name] component_ids [Offset] 3 [Type] unsigned char [Size] 1 [Description] 
This is an index to an array of catalogue number suffixes. The list is read from the stars_hip_component_ids.cat file. The value of this field turns out to be the line number in the file - 1
Star Catalogue Format - Stellarium Wiki