Int 21  - European MS-dos 4.0 - "aexec" - Execute Program In Background    [!]

   AH = 80h
   CX = mode
       0000h place child in zombie mode on exit to preserve exit code
       0001h discard child process and exit code on termination
   DS:DX -> ASCIZ full program name
   ES:BX -> parameter block (as for AX=4B00h)

Return: CF clear if successful
       AX = Command Subgroup ID (CSID)
   CF set on error
       AX = error code (see AH=59h)
Program: European MS-DOS 4.0 was written for Siemens in Germany and then used
     by several other European OEMs; its release falls between mainstream
     versions 3.2 and 3.3
Desc:  asynchronously execute a program, creating a new process for it

Notes: this function is called by the DETACH command
   there is a system-wide limit of 32 processes
   the CSID is used to identify all processes that have been spawned by
     a given process, whether directly or indirectly
   programs to be run in the background must use the new executable format
     (see AH=4Bh)
   background processes may only perform asynchronous (background) EXECs,
     either this function or AX=4B04h
   background processes may execute INT 11, INT 12, INT 21, INT 2A, and
     INT 2F at any time; they may execute INT 10 and INT 16 only while
     they have opened a popup screen via INT 2F/AX=1401h; no other
     interrupts may be executed from the background
   background processes may not use drive B: or overlay their code
     segments
   see AX=8700h for an installation check
   the "NE" new executable format made its first appearance in European
     MS-DOS 4.0

See Also: AH=4Bh,AH=87h,INT 2F/AX=1400h"POPUP"