Int 2F Fn 5500  U - DOS 5+ - Command.com Interface                         [l]

   AX = 5500h

Return: AX = 0000h if an instance of COMMAND.COM is already running
   DS:SI -> entry point table

Notes: used to access the shareable portion of COMMAND.COM, which may have
     been moved into the HMA; only the primary COMMAND.COM retains this
     portion
   procedures called from a dispatcher in COMMAND's resident portion;
     most assume that the segment address of the resident portion is on
     the stack and are thus not of general use

See Also: AX=5501h