| 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.
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