I was reading a post related to the operating system of American Space Shuttles, then wondered what might Soviets have used. I found a CIA document and several forums saying that Prolog was used in the Buran. I have experience in object oriented and a decent understanding of logic programming languages but I can't find a reason why they might have chosen such a complicated way of developing a system.
According to Wikipedia the use of prolog is just a mistake in the CIA report:
Researchers at Keldysh developed two languages: PROL2 (used for real-time programming of onboard systems) and DIPOL (used for the ground-based test systems), as well as the development and debugging environment SAPO PROLOGUE
A declassified May 1990 CIA report citing open-source intelligence material states that the software for the Buran spacecraft was written in "the French-developed programming language known as Prolog", possibly due to confusion with the name PROLOGUE.