INT 21 - DOS 3.2+ internal - SET DEVICE DRIVER LOOKAHEAD FLAG
AH = 64h
AL = flag
00h (default) call device driver function 5 (non-dest read)
before INT 21/AH=01h,08h,0Ah
nonzero don't call driver function 5
Return: nothing
Notes:  called by DOS 3.3+ PRINT.COM
does not use any of the DOS-internal stacks and is thus fully
reentrant
SeeAlso: AH=08h,AH=0Ah,AX=5D06h

See also: 2101

2164 - DOS 3.2+ internal - SET DEVICE DRIVER LOOKAHEAD FLAG