Electronica B3-21 is the first Soviet programmable microcalculator with reverse Polish notation designed to provide calculations for complex engineering and scientific projects in the realm of physics, automation, electrical engineering and electronics. It was extensively used for education purposes, in healthcare institutions and space industry. The device’s calculation capacities were overwhelming: it can be viewed as a veritable portable mini PC.
The calculator was developed in early 1977 and hit the market at the beginning of 1978. The initial sale price was RUB 350. Later on, it was reduced to RUB 190, and then to RUB 80.
The first B3-21 models featured red LED displays, which were later replaced by the easily recognisable green vacuum fluorescent displays.
The calculator had two operating registers (X or R0, and Y or R1), seven memory registers (R2—R8) and six registers of circular bidirectional stack memory (C1—C6).
The calculator can perform four arithmetic operations, calculate trigonometric, logarithmic, exponential, power and other functions, retrieve constant π (with a dedicated key available), record information into memory registers, replace data in the circular stack memory, change number signs, exchange information between two operating registers, and clear the operating and display registers (up to 30 functions and operations).
To enhance the programming capacities and facilitate software control and debugging, the microcalculator features a special memory unit capable of storing 60 programme steps.
Unlike Electronica B3-19M, B3-21 has two prefix keys — F and P. F is the prefix key for operations marked with black, whereas P is used for operations highlighted in red. Prefix keys are also used to record numbers or extract them from the registers (P is for recording, F is for extraction).
The fifth issue of the Radio Magazine describes how the calculator can be used to assess the students’ performance. It suffices to feed relevant programmes and subprogrammes into the calculator, and the calculator becomes a convenient assessment tool.
For power supply the microcalculator can use both four AA batteries and a line adapter.
Size — 185×100×44 mm. Weight — 390 g or less.
