Setun (Russian: Се́тунь) was a balanced ternary computer developed in 1958 at Moscow State University. The device was built under the lead of Sergei Sobolev and Nikolay Brusentsov. It was the only modern ternary computer, using three-valued ternary logic instead of two-valued binary logic prevalent in computers before and after Setun's conception. The computer was built to fulfill the needs of the Moscow State University and was manufactured at the Kazan Mathematical plant. Fifty computers were built and production was then halted in 1965. In the period between 1965 and 1970, a regular binary computer was then used at Moscow State University to replace it. Although this replacement binary computer performed equally well, it was 2.5 times the cost of the Setun. In 1970, a new ternary computer, the Setun-70, was designed. The computer was named after the Setun River, which ends near Moscow University.
DSSP (Dialog System for Structured Programming) is a programming language designed for Setun. It was created by students in the laboratory of Nikolay Brusentsov at the Computer Science department of the Moscow State University in 1980. The 32-bit version was created in 1989.
DSSP is similar to the Forth programming language; both are examples of stack-based languages. It may be seen as an early fork from Forth, yet with roots extending to the ternary logic computers like Setun.
Relying on the principle of "one word of text - one word of machine code", DSSP stays very close to the actual machine in structure. It uses Reverse Polish Notation, which is a stack-oriented form of calculating.
The first document in English regarding this obscure language distinguishes DSSP from Forth in the following manner: "DSSP was not invented. It was found. That is why DSSP has not versions, but only extensions. Forth is created by practice. DSSP is created by theory. It is not a word."
See also 
- Klimenko, Stanislav V.: Computer science in Russia: A personal view. IEEE Annals of the history of computing, v 21, n 3, 1999
- Malinovski, B. N.: Istorija vychislitel’noj tekhniki v licakh. Kiev, 1995, (in Russian)
- Žogolev, Y. A.: The order code and an interpretative system for the Setun computer. USSR Comp. Math. And Math. Physics (3), 1962, Oxford, Pergamon Press, p 563-578 (in English)
- G. Trogemann, A. Y. Nitussov, W. Ernst (Hg.), Computing in Russia: The History of Computer Devices and Information Technology revealed. Vieweg Verlag, July 2001 (in English)
- Hunger, Francis: SETUN. An Inquiry into the Soviet Ternary Computer. Institut für Buchkunst Leipzig, 2008, ISBN 3-932865-48-0 (Englisch, German)
- Development of ternary computers at Moscow State University
- Nikolai Brusentsov's Setun entry
- Pioneers of Soviet Computing
- Serija EBM Setun (in Russian)
- Сайт материалов по троичной информатике(in Russian)
- Online simulation of Setun ternary computer
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