The ENIAC Type Arithmetic System was prototyped in 1950 by Joh Kenzo and others at Osaka University. The system was designed and prototyped in 1950 by Joh Kenzo, Makinouchi Saburo and Yasui Hiroshi of the Faculty of Engineering of Osaka University , based on references explaining the mechanism of the ENIAC's arithmetic unit. This was done with the aim of conducting follow-up experiments on the arithmetic unit of the first electronic computer, the ENIAC, which was announced in the United States in 1946. This was a 4 digit decimal arithmetic unit based on vacuum tubes. It could store 4 digits in memory (2 digits each on the left and right), add and subtract 2 digits + 2 digits, perform transfer in 200É sec, and display results or store them in memory.
After this, Joh Kenzo (together with Makinouchi Saburo and Yasui Hiroshi) began work to develop a true binary vacuum tube computer based on the EDSAC instruction set. This electronic computer used 1,500 vacuum tubes, 4,000 diodes, and solid delay line memory for 1,024 words. It had a clock speed of 1MHz (clock speed of the EDSAC was 500KHz). The instruction format was the single-address type, with 20 bits per word. Numerical words were normally 40 bits (long words comprised of two words), but 20 bit short words were also used. As memory elements, the machine used 32 glass solid delay line elements with a memory capacity of 32 words (developed by the Electrotechnical Laboratory). Due to issues like an inadequate budget and personnel, it took a long time to purchase parts, and fabricate and adjust the machine. At the final stage of adjusting the entire computer, the university decided to introduce a Japanese commercial computer, so overall finishing of the Osaka University vacuum tube computer was suspended.
This ENIAC Type Arithmetic System is regarded as the first vacuum tube arithmetic unit made in Japan. The actual ENIAC Type Arithmetic System and binary vacuum tube electronic computer are currently preserved in the Special Materials Room of the Faculty of Engineering of Osaka University.