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+
   this function sets the program's return code (ERRORLEVEL) to 00h
   execution continues at the address stored in INT 22 after DOS performs
     whatever cleanup it needs to do (restoring the INT 22,INT 23,INT 24
     vectors from the PSP assumed to be located at offset 0000h in the
     segment indicated by the stack copy of CS, etc.)
   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