The first modest trials of replacing several mechanical computing elements in conventional desk top calculators by electrical components have already been attempted in Japan round about 1939 by H. Yamashita. The principle of program control, however, was not applied until the American automatic computer developments became known after the end of World War II. The application of the theory of switching to relay networks has been brought to a high standard at an early stage in Japan. Therefore, it was but a natural approach to utilize in practice the results obtained by the theoretical investigations for the design of computers. We started with the construction of relay computers. Here, the large-scale relay computer ETL Mark II installed at the Electrotechnical Laboratory (ETL) of the Ministry of International Trade and Industry, belongs to the most significant developments. This computer the design principles of which are described in the first part of this contribution is, since it has been completed in November 1955, actively used for the solution of various kinds of mathematical and scientific problems such as logical mathematics, atomic power reactor calculations, numerical weather forecasting, etc.
The second phase of development in the digital computer field in Japan started with the invention of the parametron by Eiichi Goto in 1954. It is characterized to a large extent by original contributions of Japanese scientists, which also found vigorous resonance in other countries. In the passed years the Japanese industry has developed a relatively large variety of medium-speed parametron computers and put them on the market. In the second and third part of this contribution the principle of the parametron and some memory systems suited for parametron computers are discussed.
Apart from the parametron, attention has also been paid to the development of highly efficient transistor circuits. The design of the ETL Mark IV computer with junction type transistors as dynamic flip-flops is a characteristic in this respect. In the fourth part there is shortly described the operation of the electronic basic circuits. Additionally, the most significant descriptive data of the prototype ETL Mark IV are given.
Tohru Motooka of the Tokyo University has investigated computing and control circuits which merely consist of magnetic cores and resistances (diodes are eliminated). The magnetic circuitry developed by him and described in the fifth part appears to be suitable specially for digital circuits in control engineering.
The discovery of the tunneling effect in semi-conductor diodes by Leo Esaki and the development of the tunnel diode (accordingly designated “Esaki Diode”) is, as can already be seen now, having significant consequences with respect to the development of the next generation of computer switching circuits. Many symptoms indicate that the Esaki Diode will very soon hold a predominant position among the electronic elements. The Esaki Diode and some of its characteristic digital circuitry is the subject of the sixth part of this contribution.
In the final part VII a novel type of logical circuits is described aiming at the accomplishment of complex computer logic in one-step operation. The basic circuits, i. e. adder, shifting register, detector, and selective transmitter, comprise common transistors, diodes, and pulse transformers. By combining these circuits, logical networks of a great variety can be designed which are used in the construction of a high-speed parallel computer for performing arithmetic operations in the ten microseconds order of magnitude.