A calculator is a device that is used for performing numerical calculations. The first calculator was the abacus, which was constructed as a wooden frame with beads sliding on wires. Calculations were made by moving these beads up and down the wires. The abacus was very much in use long before the adoption of the written Arabic numerals, and it is still used by some merchants in China and elsewhere in Asia.

Though the calculator is a handheld microelectronic device, in the past, they were as large as the computer of today. The first few computers were mechanical desktop devices that were replaced by electromechanical desktop calculators and then by electronic calculators. Nowadays, students in developed countries are allowed to use calculators for schoolwork. However, there is still a debate going on about if it is right to introduce calculators to children, as they may then lose their capacity of calculating mentally without the use of a calculator.

The modern-day calculator is designed not only for calculations, but also to perform specific operations. The complexity of the computer varies with the purpose of the calculator. There are also calculators that help calculate the monthly installments of loans, mortgages, and auto loans. They are called loan calculators, mortgage calculators, and auto loan calculators, respectively.

The simple calculator used for simple calculations has four main parts. There is a power source, which may be either a battery or a solar panel; a display from LED lights; electronic circuitry; and a keypad comprising of the ten digits, the four arithmetic functions, the equal sign, the decimal point, on and off buttons, a cancel button and some other basic functions. There are more complex scientific calculators that are useful for engineering and accounting. They help in trigonometric, statistical, and mathematical functions that make the work easier for the scientist and engineer. The most advanced calculators can even display graphics, are programmable and include computer algebra systems features.