New Delhi, Sept. 1 -- Apple is entering a new leadership era. John Ternus has become chief executive officer of Apple effective September 1, succeeding Tim Cook after a 15-year run at the helm of the technology giant.

Cook is not leaving Apple. He moves into the newly configured role of executive chairman of the board, where he will continue to be involved in certain areas of the company, including engagement with policymakers around the world. Ternus also joins Apple's board of directors effective September 1.

The transition was first announced by Apple on April 20 and was unanimously approved by its board following what the company described as a long-term succession planning process.

For Apple, the change is significant not simply b...