Int 2F Fn 1902  U - DOS 4.x Only Shellb.com - Command.com Interface        [l]

   AX = 1902h
   ES:DI -> ASCIZ full filename of current batch file, with at least the
        final filename element uppercased
   DS:DX -> buffer for results

Return: AL = 00h  failed, either
         (a) final filename element quoted at ES:DI does not match
             identity of shell batch file quoted as parameter of most
             recent call of SHELLB command, or
         (b) no more Program Start Commands available.
   AL= FFh  success, then:
       memory at DS:[DX+1] onwards filled as:
       DX+1:   BYTE    count of bytes of PSC
       DX+2: N BYTEs   Program Start Command text
           BYTE    0Dh terminator
Explanation: COMMAND.COM executes the result of this call in preference to
   reading a command from a batch file. Thus the batch file does not
   advance in execution for so long as SHELLB provides PSCs from its
   workspace. The PSCs are planted in SHELLB workspace by SHELLC, the user
   menu interface. The final PSC of a sequence is finished with a
   GOTO COMMON, which causes a loop back in the batch file which called
   SHELLC so as to execute SHELLC again. The check on batch file name
   permits PSCs to CALL nested batch files while PSCs are still stacked
   up for subsequent execution.