Int 21 Fn 00  - DOS 1+ - Terminate Program                                 [D]

   AH = 00h
   CS = PSP segment

Notes: Microsoft recommends using INT 21/AH=4Ch for DOS 2+
   execution continues at the address stored in INT 22 after DOS performs
     whatever cleanup it needs to do
   if the PSP is its own parent, the process's memory is not freed; if
     INT 22 additionally points into the terminating program, the
     process is effectively NOT terminated
   not supported by MS Windows 3.0 DOSX.EXE DOS extender

See Also: AH=26h,AH=31h,AH=4Ch,INT 20,INT 22