Former Microsoft programmer Dr Charles Simonyi has signed up for a holiday on the International Space Station.

The 51 year-old programmer, who was instrumental in the creation of Microsoft's Word and Excel packages, has handed over $20m for the trip and has begun training at the Yuri Gagarin Cosmonaut Training Centre in Star City ready for launching in September.

"Like with any long-term plan, I had to make reservations," said Dr Simonyi, who is currently head of development firm Intentional Software.

"I have always dreamed of the wonder of spaceflight, and the exploration of space has always inspired me. I consider my future flight to be a small part of an important trend to make space accessible to more people, not just to experts. "

The Hungarian-born programmer will be the fifth space tourist since the International Space Station opened in 1998.

American businessman Dennis Tito, scientist Gregory Olsen and South African Mark Shuttleworth have already been up, and Japanese businessman Daisuke Enomoto will become the fourth later this year.

"Dr Simonyi is a true visionary and one of the leading technology entrepreneurs in the world," said Eric Anderson, president of Space Ad ventures, which organises the trips into orbit.

"He was a major contributor to the dawn of the computer age by creating software applications that are now used by millions of people every day.

"He is also a seasoned pilot and very knowledgeable about aerospace technology and aviation. It has been an honour to work with Dr Simonyi and we look forward to his initiation of training and eventual launch."

Dr Simonyi already has a pilot's licence and has said he is looking forward to using his software skills on the trip.