21FA INT 21 - DOS v2.11-2.13 - OEM FUNCTION
21FA INT 21 - DoubleDOS - TURN OFF TASK SWITCHING
21FA INT 21 - VIRUS - "Cinderella 2" - INSTALLATION CHECK
21FA--DX5945 INT 21 U - PC Tools v7+ VDEFEND, VSAFE, VWATCH - API
21FAFF INT 21 U - IBM PC-DOS - KEYBGK - SELECT KEYBOARD LAYOUT