COMPUTER ASSOCIATES <CA> STARTS BPI <BPII> BID Computer Associates International Inc said it has started its previously-announced 1.92 dlr per share tender offer for all shares of BPI Systems Inc. In a newspaper advertisement, the company said the offer, which has been approved by the BPI board and is to be followed by a merger at the same price, is conditioned on receipt of at least 1,813,742 shares. The offer and withdrawal rights expire May 15 unless extended. In addition to shares sought in the tender, shareholders of BPI owning 1,951,720 shares or 34.6 pct have agreed to sell their shares to Computer Associates for the tender price.