Microsoft chief Steve Ballmer to retire

Microsoft chief executive Steve Ballmer is to retire from the technology giant within the next 12 months.

Shares in Microsoft, which was criticised for its slow response to the booming market for mobile devices, leapt 9% on the news.

Mr Ballmer said in a statement: "There is never a perfect time for this type of transition, but now is the right time."

Watch a clip of Mr Ballmer delivering a presentation in 2000, the year he succeeded Microsoft founder Bill Gates.