Microsoft CEO Steve Ballmer is expected to retire within the next year, according to the software company.

NEW YORK - Microsoft CEO Steve Ballmer, who succeeded founder Bill Gates as CEO, will retire within the next 12 months.

The world's biggest software company did not name a successor.

Microsoft Corp.'s stock shot up 9 percent in premarket trading following the news.

Ballmer, 57, first met Microsoft founder Bill Gates in 1973 while they were living down a dormitory hall from each other at Harvard University. He joined Microsoft in 1980 to bring some business discipline and salesmanship to a company that had just landed a contract to supply an operating system for a personal computer that IBM would release in 1981.

Ballmer did the job so well that he would become Gates' sounding board and succeed him as CEO in 2000.