Calculators have been used in mathematics in the fourth grade of primary school. Calculator is generally composed of arithmetic unit, controller, memory, keyboard, display, power supply and some optional peripheral devices and electronic accessories, and is composed of manual or mechanical equipment. The arithmetic unit and controller of low-level calculator realize simple serial operation through digital logic circuit, and its random access memory has only one or two units for accumulation storage.

Modern development:

Early calculators were purely manual, such as abacus and calculation. An abacus is usually made of sliding beads. In the west, abacus had been used for centuries before the popularity of Indian Arabic numerals, and it was still widely used in accounting and business in modern China. Then came the mechanical calculator.

/kloc-At the beginning of the 0/7th century, the computing tools in western countries developed greatly. British mathematician Napier invented "Napier Arithmetic", and British priest Orchard invented the cylindrical logarithmic ruler, which can not only do addition, subtraction, multiplication, division and square root operations.