Yoshiteru Ishii was born on March 16th in 1928. He joined NEC Corporation in 1951 after he graduated from University of Tokyo. His major was Electronics Engineering. Since NEC started computer business and contributed greatly for NEC's success of computer business in the world.

First, he worked as a NEC side project leader of joint development of SENAC-1 (NEC name: NEAC-1102) with Oizumi and his associates of Tohoku University and delivered it to Tohoku University in 1958. As there was almost no information about computer in those days, specifications were decided after repeated discussions with participants from Tohoku University. It was the first large scale parametron computer in Japan.

Ishii paid attention to the possibility of high speed of transistor and promoted transistorized computer. The first development of small size transistorized computer NEAC-2202 was completed in 1959. NEAC-2202 was very early transistorized TSS system computer which enabled simultaneously common use of central processor unit with 7 input/output systems by time sharing method. By this invention titled as "Automatic Computing System" he received the Science and Technology Agency Award of National Commendation for Invention in 1968.

Since he assumed product planning manager in 1964, he performed major roles on the NEC's data processing business at both fields of product planning and product development. At the joint conference of four electronics institutes held in around 1978 he participated as a panelist in the panel discussion titled as "Can LSI be used for computer". There he stated the benefits of using LSI for computer as well as the method to overcome its difficulties.

Ishii performed very important roles at product planning, developments and business promotions by being involved in the general management of operations and developments of general purpose computer NEAC 2200 series, ACOS series, SBC and personal computers. Through his promotions, for example, NEC announced the sales of ACOS system 250 February in 1979. It was just one week after IBM announced new computer 4331 and 4341 in USA. NEC's announcement attracted remarkable attentions of computer industry as it responded earliest in the world to the new IBM series and drove NEC's data processing business to its outstanding success thereafter. NEC announced sales of 16bit personal computer PC-9800 in 1982 and took No.1 share of personal computer business in Japan. He succeeded to make the business contracts in 1984 to supply and provide technical know-how of very large scale computer ACOS1000 and its successor models to both companies, Honneywell in United States and Bull in France and thus succeeded in establishing the sales structure of NEC's very large scale computer at world three major markets of Unites States of America, Europe and Japan.

Ishii resigned the Senior Executive Vice President of NEC in charge of NEC's data processing business in 1991 and joined Anritsu Corporation as Chairman of the Board. He then assumed Director and Counselor of Anritsu Corporation in 1999.

He received IPSJ Contribution Award from Information Processing Society of Japan (IPSJ) in 1994 and was elected as the Honorary Member in 1995.

He died on June 8, 2018.