SAN FRANCISCO – Boosted by upbeat investor reaction to its strong earnings report this week, Apple Inc. on Thursday became the second-largest company on the S&P 500 Index in terms of market capitalization, surpassing software giant Microsoft Corp.

According to Standard & Poor’s index services unit, Apple reached a market cap of $241.5 billion to pass that of Microsoft’s $239.5 billion market capitalization.

Apple trails only Exxon Mobil and its market cap of more than $300 billion.