The company, part of the Raspberry Pi Foundation, a UK charity that promotes computing among young people, priced its share offering at pound2.80 each, for a total value of pound541.6 million ($690 million).

Soon after trading began, the share price soared 40 percent to pound3.92.

"The reaction that we have received is a reflection of the world-class team that we have assembled and the strength of the loyal community with whom we have grown," Raspberry Pi chief executive Eben Upton said after the share float.

Founded in 2012, the company based in England's university city Cambridge has sold tens of millions of its credit-card-size computers.

The device, whose latest edition sells for around pound110 in Britain, is used mainly to teach coding to children and promote computing in developing countries.