The Dow and other major indexes closed at record highs on Tuesday. Microsoft joins an elite club of one...

The company is testing new versions of each product with OLED screens, according to people with knowledge of the matter. The technology — short for organic light-emitting diode — delivers richer colors and deeper contrasts than current LCD displays. The iPad mini will likely be the first of the three to gain the upgrade, with an OLED-equipped model arriving as early as next year, said the people, who asked not to be identified because the products haven’t been announced...

Microsoft's 2% gain today has given it a market value greater than $4 trillion for the first time on record. Apple also crossed the $4 trillion mark earlier in Tuesday's session, though most of those gains slipped away and the stock closed below the milestone. Microsoft and Apple are following Nvidia, which became the world's first $4 trillion company in July and today closed with a market cap near $4.9 trillion...

The sky-high valuations highlight the investor frenzy around artificial intelligence. Earlier in the day, OpenAI said it has reorganized its ownership structure and converted its business into a public benefit corporation after two crucial regulators, the Delaware and California attorneys general, said they would not oppose the plan...