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Calculators
A calculator is a device for performing
numerical calculations. It should not be confused with
a calculating machine. Nowadays many people have a calculator
with them as part of their mobile phone and/or personal
digital assistant. Engineers and accountants make use
of calculators for problems where a computation is not
complex enough to demand the use of a general-purpose
computer. Students use calculators for schoolwork. Also,
some wrist watches contain a calculator (although this
was more a fad of the 1980s).
Today calculators are electronic, and
are made by numerous manufacturers, 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. Only a very few companies develop and
make modern professional engineering and finance calculators;
the most well-known are Casio, Hewlett-Packard (HP) and
Texas Instruments (TI). Such calculators are good examples
of embedded systems.
In the past, mechanical and clerical
aids such as abaci, comptometers, Napier's bones, books
of mathematical tables, slide rules, adding machines,
were used for serious numeric work, and the word "calculator"
denoted a person (most often female) who did such work
for a living using such aids as well as pen and paper.
This semi-manual process of calculation was tedious and
error-prone.
Electronic calculators
Today most calculators are handheld
microelectronic devices, but in the past some calculators
were as large as today's computers. The first mechanical
calculators were mechanical desktop devices, which were
soon replaced by electromechanical desktop calculators,
and then by electronic devices using first thermionic
valves, then transistors, then hard-wired integrated circuit
logic.
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.
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