Bill Gates, the billionaire chairman of Microsoft, received an honorary knighthood today for his charitable work and his achievement in creating the world's most successful software company.

Mr Gates and his wife, Melinda, met the Queen and the Duke of Edinburgh at Buckingham Palace for the ceremony. Despite receiving the KBE, or Knight Commander of the Order of the British Empire, Mr Gates will not be known as 'Sir', a title reserved for British citizens.

Through the Bill and Melinda Gates Foundation, the couple have given away billions of dollars, most being spent on programmes to improve health in developing countries. Malaria and Aids have been a particular focus, as have childhood diseases. Recently the foundation donated $750m to the Global Alliance for Vaccines and Immunisation, which Mr Gates was instrumental in setting up.

Honorary knighthoods are awarded by the Queen, on the advice of the Foreign Office, to those who have made an important contribution to British interests. Microsoft directly employs almost 2,000 people in the UK, including 80 researchers at the Microsoft Research Cambridge, the company's first research laboratory outside the United States, which was set up in 1997.

Before his private audience with the Queen, Mr Gates met Prince Philip, who is chancellor of Cambridge University, and spoke about the facility.

During the brief ceremony, when the KBE insignia was handed to Mr Gates, the Queen talked about computers, which she does not use.

"It's not as natural for her as it is for young people," said Mr Gates, who is 50 in October.

"I am humbled and delighted. I'm particularly pleased that this honour helps recognise the real heroes our Foundation supports to improve health in poor countries. Their incredible work is helping ensure that one day all people - no matter where that are born - will have the same opportunity for a healthy life," Mr Gates said in a statement.

"This honour is particularly poignant given the deep connections that Microsoft enjoys with the United Kingdom. Over the past 20 years we have benefited greatly from strong business partnerships and the tremendous wealth of talent and creativity of our UK employees and researchers.

"These businesses and these employees have been an important part of the positive impact technology has had on economic growth and on the lives of people in the UK. I am proud of this special relationship and in the role we played in the development of the UK technology industry," he said.

Mr Gates is regularly placed at the top of the Forbes magazine rich list, and is worth an estimated $46bn (£24bn). The Bill and Melinda Gates Foundation has an endowment of about £19bn.