A **calculator** is a small special-purpose device for performing numerical calculations. It shouldn't be confused with a calculating machine.
Nowadays many people always have a calculator with them as part of their mobile phone and/or personal digital assistant.
Engineers and accountants often make use of calculators, where a computation is not complex enough to demand the use of a general-purpose computer.
Children often use calculators for school work. Also, some wrist watcheses contain a calculator (although this was more a fad of the 1980s).

TI-85 graphing calculator

Today calculators are electronic, but in the past mechanical and clerical aids such as slide rules, abaci, comptometers, books of mathematical tables and Napier's bones were used, and a "calculator" was a person (most often female) who made calculations using pen(cil) and paper.

A pocket calculator is a small battery-powered or solar powered electronic digital computer made possible by integrated circuit and semiconductor technology. Typically they are limited to an 8 – 10 digit single-number display and a few basic functions of arithmetic, but some modern ones have more of the features of a general-purpose computer. Pocket calculators rendered the slide rule obsolete.

Calculators vary in their capabilities. Some are limited to only basic arithmetic; others support trigonometric and other mathematical functions. The most advanced modern calculators are programmable, can display graphics, and include features of computer algebra systems.

The first pocket-sized model, the 901B (measuring 5.2" x 3.0" x 1.5" / 131mm x 77mm x 37mm), came out in the fall of 1971 from Bowmar, with four functions and an eight-digit red LED display, for $240, while in August 1972 the four function *Sinclair Executive* became the first slimline pocket calculator (5.4" x 2.2" x 0.35" 2.5oz / 138mm x 56mm x 9mm 70g) retailing for around $150 (£7979).

The first with *scientific* functions was the 1972 HP-35 from Hewlett Packard (HP); it, along with all later HP engineering calculators, used Reverse Polish Notation (RPN).

Most common among early scientific calculators was the TI-30 from Texas Instruments (TI). The first *programmable* hand-held calculator was the HP-65, in 1974; it had a capacity of 100 instructions, and could store and retrieve programs with a built-in magnetic card reader. In 1979, HP released the first *alpha-numeric*, programmable, expandable calculator, the HP-41C. It could be expanded with RAM (memory) and ROM (software) modules, as well as peripherals like bar code wands, floppy disk drives, paper-roll printers, and miscellaneous communication interfaces (RS-232, HP-IL, HP-IB).

Monroe manual digital calculator

The two leading manufacturers, HP and TI, released steadily more feature-laden calculators during the 1980s and 90s. At the turn of the millennium, the line between a graphing calculator and a PDA/ handheld computer was not always clear (forgetting the keyboard for the sake of the argument), as some advanced calculators such as the TI-89 and HP-49 could differentiate and integrate functions, run word processing and PIM software, and connect by wire or IR to other calculators/computers.

In March 2002, HP announced that the company would no longer produce calculators, which was hard to fathom for some fans of the company's products; the HP-48 series in particular had an extremely loyal customer base. Nevertheless, HP continued producing calculators, but the latest models as of 2003 reportedly didn't have the mechanical quality HP's earlier calculators were famous for (instead featuring the more "youthful" look and feel of contemporary competing designs).

The business calculator HP-12C is still produced. It was introduced in 1981 and is built until today with nearly no changes. For 2003 several new models were announced, including an improved version of the HP-12C, the "HP-12C platinum edition".

The word "calculator" is occasionally used as a pejorative term to describe an inadequately capable general-purpose computer, as discussed in the Jargon file.

- On slide rules and mechanical calculators
- On TI's US Patent No. 3,819,921
- The Museum of HP Calculators
- Museum of Soviet Calculators
- HP Calculators' Wiki
- Vintage Calculators
- GraphCalc, an Open Source graphing calculator program that runs on a computer