After graduating at the top of his mathematics class in 1958, Leslie Green joined the University of Toronto’s recently-created Computer Centre as one of Canada’s first computer programmers. He later worked for a cross-disciplinary consulting firm and helped the City of Toronto to forecast traffic flows and computerize traffic lights. After advising Ontario ministries on computer policy, he joined the Food and Agricultural Organization in Rome, Italy, where he employed mathematics to reveal causes of delays of the World Food Program’s aid shipments to those in need. He then led the statistics service at the Organization for Economic Cooperation and Development (OECD) to make OECD’s data electronically accessible to organizations worldwide. After creating a method for teachers to design educational software for their students, he taught it to hundreds of educators in Ontario, Europe and Africa.