Mr. Williams was long considered a leading candidate to replace Tim Cook as the company’s next chief executive.

Apple Inc. Chief Operating Officer Jeff Williams is retiring as the company’s longtime No. 2, marking a major changing of the guard at an already tumultuous time for the iPhone maker.Williams will step down as COO this month before retiring from the company later in the year,

When a company as huge and influential as Apple makes a change in its top leadership, the world pays attention, since a high-level leadership change could affect the future trajec