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For example, there are graphing calculators which focus on graph-centered math like trigonometry and statistics. Also, modern calculators are more portable than most computers, though some PDAs are comparable in size to handheld calculators.
OverviewIn the past, mechanical clerical aids such as abaci, comptometers, Napier's bones, books of mathematical tables, slide rules, or mechanical adding machines were used for numeric work. . This semi-manual process of calculation was tedious and error-prone. Modern calculators are electrically powered and come in countless shapes and sizes varying from cheap, give-away, credit-card sized models to more sturdy adding machine-like models with built-in printers.
Electronic calculatorsIn the past, some calculators were as large as today's computers. The first mechanical calculators were mechanical desktop devices which were replaced by electromechanical desktop calculators, and then by electronic devices using first thermionic valves, then transistors, then hard-wired integrated circuit logic. Today, most calculators are handheld microelectronic devices.
Basic configurationThe complexity of calculators varies with the intended purpose. A simple modern calculator might consist of the following parts:
A power source, such as a battery or a solar panel or both;
A display, usually made from LED lights or liquid crystal (LCD), capable of showing a number of digits (typically 8 or 10);
Electronic circuitry;
A keypad containing:
The ten digits, 0 through 9;
The decimal point;
The equals sign, to prompt for the answer;
The four arithmetic functions (namely, addition, subtraction, multiplication and division);
A Cancel (or clear) button, to clear the current calculation;
On and off buttons;
Other basic functions, such as square root and percentage (%).;
Since the late-1980s, simple calculators have been installed in other small devices, such as mobile phones, pagers or wrist watches.
Scientific and financial calculatorsMore complex scientific calculators support trigonometric, statistical and other mathematical functions. The most advanced modern calculators can display graphics, and include features of computer algebra systems. They are also programmable; calculator applications include algebraic equation solvers, financial models and even games. Most calculators of this type can print numbers up to ten digits or decimal places in full on the screen. Scientific notation is used to notate numbers up to a limit chosen by the calculator designer, such as 9.999999999*1099. If a larger number or a mathematical expression yielding a larger number than this is entered (a common example comes from typing "100!", read as "100 factorial") then the calculator might simply display "error".
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