noun
adder; adding machine
Refers to a device that performs addition, either a mechanical adding machine or an electronic adder circuit.
この加算器は二進数の足し算ができる。
This adder can perform binary addition.
昔の事務所には加算器が置いてあった。
Old offices used to have adding machines.
計算機 is a general term for a calculator or computing machine, while 加算器 specifically refers to a device that adds.
Compound of 加算 (addition) and 器 (device). The alternate form 加算機 uses 機 (machine) instead.