(a)an order passed on or before or after the 1st day of June, 1988, by the Assessing Officer shall-include an order passed by the Deputy Commissioner in exercise of the powers or in performance of the functions of an Assessing Officer conferred on or assigned to him under orders or directions issued by the Board or by the Chief Commissioner or Director-General or Commissioner authorised by the Board in this behalf under section !20 of the Income-tax Act read with section 7 of this Act;