Hosaka Mamoru: born in 1920, graduated from University of Tokyo in 1942, served as technical officer in the Japanese Navy during the War. 1946-1959: research engineer in Japanese National Railways. 1959-1981: Professor of University of Tokyo and also Tokyo Institute of Technology. 1981-1997: Professor of Tokyo Denki University, and a member of the Board of Directors. 1977-1978: President of IPSJ.

He had interest in computer in 1951, when he learned that digital computer had been invented in USA. While he was at MIT in 1952-1953, he gathered information on digital computers and met Professor N. Wiener.

After returning to Japan, though there was no computer in Japan. he whose main task was not in computer field, organized a spontaneous group in the Railway Technical Research Institute of Japan National Railways (JNR) to study computer technology and its probable application in future railway business, In 1955, after his group was authorized, he proposed to the headquarter sections of the JNR on real time control systems such as freight car dispatch and seat reservation of trains. He also succeeded in persuading the top executives of the Institute to import Bendix-G15 computer to enhance group members' ability. These efforts resulted in successful construction of a prototype seat reservation system MARS-1. Ohno Yutaka, one of members of his study group, contributed to its development.

Jan.1960, MARS-1, the first on-line real-time seat reservation system for railway train, began services for four business express trains between Tokyo and Osaka, 3600 seats each day and for 15 days ahead. Since it proved very reliable and useful, JNR trusted computers and decided to expand MARS-1 to cover various trains of JNR as well as to integrate all tasks of seat reservation business.

Hosaka analyzed the requirements for future reservation system and concluded that mere expansion of the MARS-1 could not meet large scale integrated operations and proposed a task sharing multi-computer system: a main computer around which a communication computer, a table search computer, a seat file computer are connected. The main computer controls the sub-computers to make flow of tasks optimally to obtain maximum throughput from the system. JNR, accepting his proposal, ordered its construction to Hitachi Ltd. This became the first on-line real time large scale computer system in Japan. Though, afterward, the method adopted became usual practice in computer technology, in 1960 it was seemed quite strange to computer experts in Japan, who only knew single task operation.

With collaboration of the many person of JNR and Hitachi, its construction was completed and JNR began to use the system, which was named MARS-101, from Feb. 1964. The system has evolved since then according to increasing demands to the system and along with to advancing computer technology. It has been widely known by general peoples as "Green Windows of JR".

Hosaka's works after MARS system, were the first computer graphics system in Japan and researches on CAD whose results were applied especially in car industry in Japan. He also consulted for construction of the on-line computer system of Tokyo Stock Exchange. For his achievements of researches, he received several prizes including one by the Japan National Academy. His five research papers were awarded by three academic societies in Japan.

He died on Oct. 26, 2016.