Int 2F/AX=48C1h/BL=00h

AX = 48C1h
BL = 00h

Return:
AX = 0000h if installed
BX = VSTACK resident segment

Program: VSTACK is a resident backscroll utility included as part of the PCED package by Cove Software

Note: Chains if BL <> 00h on entry

See Also: AX=48C0h - AX=48C2h