S. 263: Commissioner-Revision of orders prejudicial to revenue-Carry forward and set off of accumulated loss and unabsorbed depreciation-Amalgamation-Demerger-There was no error per se in the order of assessment, and the direction under the order of revision amounted to a mere roving enquiry and the same was set aside.[S.2(19AA), 2(IB), 72A(2), 72A(4)]