Int 2F Fn AE00  U - DOS 3.3+ Internal - Installable Command - Installatio  [l]

   AX = AE00h
   DX = FFFFh
   CH = FFh
   CL = length of command line tail (4DOS v4.0)
   DS:BX -> command line buffer (see below)
   DS:SI -> command name buffer (see below)
   DI = 0000h (4DOS v4.0)

Return: AL = FFh if this command is a TSR extension to COMMAND.COM
   AL = 00h if the command should be executed as usual

Notes: This call provides a mechanism for TSRs to install permanent
     extensions to the command repertoire of COMMAND.COM.  It appears
     that COMMAND.COM makes this call before executing the current
     command line, and does not execute it itself if the return is FFh.
   APPEND hooks this call, to allow subsequent APPEND commands to
     execute without re-running APPEND

Format of command line buffer:
Offset Size    Description
 00h   BYTE    max length of command line, as in INT 21/AH=0Ah
 01h   BYTE    count of bytes to follow, excluding terminating 0Dh
      N BYTEs  command line text, terminated by 0Dh

Format of command name buffer:
Offset Size    Description
 00h   BYTE    length of command name
 01h  N BYTEs  uppercased command name (blank-padded to 11 chars by 4DOS v4)