In calculator mode, the MK-87 can perform the four arithmetic operations, calculations with a constant, square rooting, percentage calculations and memory-related processes. It can also store up to 100 phone numbers. The memory mode enables the user to save 30 lines of any text with 60 symbols per line. Finally, the card index mode can store several tables with up to 20 columns. The user can protect the device’s memory with a special password, set by pressing the key symbol button.
The microcomputer could also erase all data with a special control command, search surnames, and sort phone contacts alphabetically. The device’s twelve-digit LCD scrolled horizontally.
The MK-87 ran on four STs-0,18 batteries and one FL-2016 battery; the clock was powered by a single STs-59battery.
Dimensions: 140×82×14 mm (closed), 140×175×9.5 mm (open)
Weight: up to 200 g
Sources: http://www.moscow-info.org/articles/2016/06/26/744147.phtml, http://electronika-5.ru/calc/index.php?page=base_item&mid=61.