Associate Professor Stefan Andreev investigated calculator with MOC integral systems in Bulgaria (1969). Before that, calculator used transistors. Prof. Jordan Kasabov presented Bulgarian calculator ELKA 42 in the Osaka Exhibition (1970), that wined gold medal. After that, Bulgaria produced and exported 50 000 pocet calculators to Switzerland.

He headed project "Physics and technology of thin films suitable for contemporary microelectronics" funded by BAS (2008)