Professor Ikeno Nobuichi was born in Shizuoka on 18 September 1924. He graduated from Hamamatsu Technical College in 1944. After he worked at a governmental research laboratory and served in the army, he obtained a bachelor's degree in physics from University of Tokyo in 1949. He joined Electro-Technical Laboratory in the ministry of transportation and communication, which was later reorganized and renamed as Electrical Communication Laboratories of Nippon Telegraph and Telephone Public Corporation. Throughout this period he worked in basic research as a researcher, manager and head of Ikeno Research Laboratory. He moved to University of Electro-Communications in 1979 as a professor in computer science. He died in 1988.
His research works are broad, deep and pioneering, ranging from theory (networks, information-communication, coding, switching and automata theory) to practical systems (design and implementation of electronic switching systems, computers and system software). He developed a new design theory of distributed constant circuits, by which he obtained a doctor's degree from Kyushu University. He won two awards from academic societies for his works on semi-electronic switching systems using parametrons in 1959 and on constant-weight codes in 1971. He wrote an award-winning book entitled Modern Cryptology Theory, coauthored with late K. Koyama in 1986.
As a computer scientist Ikeno was renowned for his creativity and brightness, in particular, to solve theoretical problems. He published many seminal papers in the early days of computer science. His small universal Turing machine, invented in 1958, initiated a sort of competition for minimizing the state-symbol product. Basic properties on the number of crossing points in switching networks, shown by him in 1959, are some of the earliest results in graph algorithms. His ingenious sorting algorithm, published in 1960, is in fact the same as the famous merge-insertion sort discovered independently by L. Ford and S. Johnson. His AUTO CODE system implemented on the MUSASINO-1B computer was one of the first compilers in Japan.
Besides his professional works, he wrote numerous informative, expository articles
in popular magazines on various subjects like microcomputers and puzzles. Indeed he was a celebrity in the society of mathematical puzzles. He was very well liked and respected by the people around him, because of his pleasant and generous personality.