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1. Enter the calculation by typing it in from the keyboard.
2. Press a single button or key to see the final result.
2. Press a single button or key to see the final result.<ref name ="SC">SpeedCrunch [home page on the Internet]; 2010. Available from: http://speedcrunch.org (freeware)</ref><ref name ="MPC">MagicPlot Calculator [home page on the Internet]; 2010. Available from: http://magicplot.com/calc (freeware)</ref><ref name ="CLC">Command Line Calculator [home page on the Internet]; 2010. Available from: http://www.kotiposti.net/jjhalme/clcmain.htm (freeware)</ref><ref name="FC">Formula Calculator Pty Ltd [home page on the Internet]; 2009. Available from: http://www.FormulaCalculator.com</ref><ref name="MO">Moisey Oysgelt [JavaScript Formula Calculator page on the Internet]; 2000. Available from: http://www.alemoi.com/math</ref><ref name="HS">Haxial Software Pty Ltd [calculator products page on the Internet]; 2001. Available from: http://www.haxial.com/products/calculator</ref><ref name="ABA">abaCal - Online Formula Calcuator [calculator page on the Internet]; 2012. Available from: http://www.abacal.com</ref>
This is unlike button-operated [[calculators]], such as the [[Windows calculator]] or the [[Calculator (Mac OS)|Mac OS X calculator]], which require the user to perform one step for each operation, by pressing buttons to calculate all the intermediate values, before the final result is shown.<ref>Microsoft’s Windows Operating System Calculator Accessory; 2001. Available on a Windows PC at: Start/All Programs/Accessories/Calculator</ref><ref>MotionNET [calculator product page on the Internet]; 2006. Available from: http://www.motionnet.com/calculator</ref><ref>Flow Simulation Ltd [Virtual Calc98 page on the Internet]; 2008. Available from: http://www.calculator.org/jcalc98.html</ref>
In this context, a formula is also known as an [[Expression (programming)|expression]],<ref>Reference 3, paragraphs 1 and 2 use ''formula'' and ''expression'' interchangeably</ref> and so formula calculators may be called ''expression'' calculators.<ref>Hot-Shareware.com [1st-Calculator page on the Internet]; 2009. Available from: http://www.hot-shareware.com/home-education/1st-calculator</ref> Also in this context, calculation is known as ''evaluation'',<ref>Reference 3, paragraph 1</ref> and so they may be called formula ''evaluators'', rather than ''calculators''.<ref>The Code Project [Dynamic Formula Calculator/Evaluator in VB.NET page on the Internet]; 2009. Available from: http://www.codeproject.com/KB/vb/Dynamic_Formula_Evaluator.aspx</ref>
== How they work ==
The calculation can be typed or pasted into an edit box of:
• A software package that runs on a computer, for example as a dialog box.<ref name="CLC"/><ref name="FC"/><ref name="HS"/>
• An on-line formula calculator hosted on a web site.<ref name="MO"/><ref name="ABA" />
It can also be entered on the command line of a programming language.<ref name="Python"/>
Declarative solutions are easier to understand than imperative solutions,<ref name=" Reference 13"/><ref>Roy E. Furman. Declarative Programming - Strategies for Solving Software Problems, http://www.articlesalley.com, July 2006. Available from: http://www.articlesalley.com/article.detail.php/7013/178/Education/Internet/36/Declarative_Programming_-_Strategies_for_Solving_Software_Problems</ref> and so there has been a long-term trend from imperative to declarative methods.<ref>David A. Watt. Programming language concepts and paradigms, Prentice Hall, 1990 (citation 13 at http://citeseer.ist.psu.edu/context/14802/0)</ref><ref> Tatsuru Matsushita. Expressive Power of Declarative Programming Languages, PhD thesis, Department of Computer Science, University of York, October 1998 (citation 13 at http://citeseer.ist.psu.edu/context/14802/0)</ref> Formula calculators are part of this trend.
Many software tools for the general user, such as [[spreadsheets]], are declarative.<ref>Reference 15, paragraph 6</ref> Formula calculators are examples of such tools.
== Hybrid calculators ==
There are hybrid calculators that combine typed-in formula and button-operated calculation. For example:
• Calculations can be entered entirely from the keyboard, or operations can be applied to typed-in numbers or formulas using buttons, in the same calculator.<ref>Reference 1, Buttons and The Works calculators. Available from: http://www.FC-Scientific.com and http://www.FC-Max.net</ref><ref>FormulaCalculator for MacOSX. A free Calculator available from: http://formcalc-osx.com</ref>
• Formulas can be constructed using buttons, rather than being entered from the keyboard.<ref>Gold-Software Development [LeoCalculator page on the Internet]; 2006. Available from: http://www.batchconverter.com/LeoCalculator-download-24300.shtml</ref><ref name="ABA" />
• Formula copies of button-operated calculations can be created, saved and re-loaded for application to different numbers.<ref>FarsightSoft Inc [Farsight Calculator page on the Internet]; 2008. Available from: http://www.farsightsoft.com/farsightcalculator.html</ref><ref name="ABA" />
== See also ==
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