What is the COMP-X used for?

What is the COMP-X used for? We use Micro focus mainframe express for our development work in  COBOL, recently I came across a copybook which had datatype of variables  defined as COMP-X. Please see below code for reference.     10  FCD-STATUS-KEY-1 PIC X.                         10  FCD-STATUS-KEY-2 PIC X.                         10  FCD-BINARY       REDEFINES FCD-STATUS-KEY-2 As far as I know, I dont think regular COBOL which runs on mainframe uses  I would be grateful if someone can explain what is COMP-X datatype and if COBOL for OS/390 uses this? “; ; ; ;