INT 2F U - DOS 4.x only SHELLB.COM - COMMAND.COM INTERFACE                      
	AX = 1902h
	ES:DI -> ASCIZA NUL-terminated ASCII string.	The ASCIZ string "ABC" consists of the four bytes 41h, 42h, 43h, and 00h.  Unless otherwise specified, maximum lengths given in the interrupt list do not include the terminating NUL. 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
Desc:	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.
Note:	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.