21FB INT 21 - DOS v2.11-2.13 - OEM FUNCTION
21FB INT 21 - DoubleDOS - TURN ON TASK SWITCHING
21FB INT 21 - VIRUS - "Cinderella" - INSTALLATION CHECK
21FB0A INT 21 - VIRUS - "dBASE" - INSTALLATION CHECK
21FBA0 INT 21 - VIRUS - "Groove" - INSTALLATION CHECK
21FBFB INT 21 - VIRUS - "Dir.1367" - INSTALLATION CHECK