BBN CORPORATION EXHIBIT 11.1 COMPUTATION OF NET INCOME (LOSS) PER SHARE (000's except per-share data) Three Months Ended ------------------------------------------- March 31, 1996 March 31, 1995 -------------------- -------------------- Fully Fully Primary Diluted Primary Diluted --------- --------- --------- --------- Weighted average shares outstanding 17,802 17,802 17,192 17,192 Incremental shares from use of treasury stock method for stock options (a) (a) 926 1,071 --------- --------- --------- --------- Shares used in per-share calculations 17,802 17,802 18,118 18,263 ========= ========= ========= ========= Net income (loss) $(29,141) $(29,141) $ 74,467 $ 74,467 ========= ========= ========= ========= Net income (loss) per share $ (1.64) $ (1.64) $ 4.11 $ 4.08 ========= ========= ========= ========= Nine Months Ended ------------------------------------------- March 31, 1996 March 31, 1995 -------------------- -------------------- Fully Fully Primary Diluted Primary Diluted --------- --------- --------- --------- Weighted average shares outstanding 17,670 17,670 16,873 16,873 Incremental shares from use of treasury stock method for stock options (a) (a) 991 1,221 --------- --------- --------- --------- Shares used in per-share calculations 17,670 17,670 17,864 18,094 ========= ========= ========= ========= Net income (loss) $(45,682) $(45,682) $(70,734) $(70,734) ========= ========= ========= ========= Net income (loss) per share $ (2.59) $ (2.59) $ 3.96 $ 3.91 ========= ========= ========= ========= (a) Incremental shares were not used as their effect would be antidilutive.