INT 2F - DOS 3.3, DOS 5.0 APPEND - HOOK INT 21 AX = B703h ES:DI -> INT 21 handler APPEND should chain to Return: ES:DI -> APPEND's INT 21 handler Note: each invocation of this function toggles a flag which APPEND uses to determine whether to chain to the user handler or the original INT 21 SeeAlso: AX=B700h,AX=B706h