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184 lines
8.5 KiB
HTML
184 lines
8.5 KiB
HTML
14 years ago
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"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html>
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<head>
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<title>Arduino - Float </title>
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<link rel="shortcut icon" type="image/x-icon" href="http://arduino.cc/en/favicon.png">
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{ border:1px solid #cccccc; padding:4px; background-color:#f9f9f9; }
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a.varlink { text-decoration:none; }
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--></style><script type="text/javascript">
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<div class="title"><a href='http://arduino.cc/en'>Arduino</a></div>
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<p><a class='wikilink' href='http://arduino.cc/en/Main/Buy'>Buy</a>
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<a class='wikilink' href='http://arduino.cc/en/Main/Hardware'>Hardware</a>
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<a class='wikilink' href='FAQ.html'>FAQ</a>
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<p class='vspace'></p>
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</div>
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<div id="navbar_external">
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<a class="urllink" href="http://www.arduino.cc/blog/" rel="nofollow">Blog »</a><a class="urllink" href="http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl" rel="nofollow">Forum »</a><a class="urllink" href="http://www.arduino.cc/playground/" rel="nofollow">Playground »</a>
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<div id="pagetext">
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<div id='wikitext'>
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<p><strong>Reference</strong> <a class='wikilink' href='index.html'>Language</a> | <a class='wikilink' href='Libraries.html'>Libraries</a> | <a class='wikilink' href='Comparison.html'>Comparison</a> | <a class='wikilink' href='Changes.html'>Changes</a>
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</p>
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<p class='vspace'></p><h2>float</h2>
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<h4>Description </h4>
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<p>Datatype for floating-point numbers, a number that has a decimal point. Floating-point numbers are often used to approximate analog and continuous values because they have greater resolution than integers. Floating-point numbers can be as large as 3.4028235E+38 and as low as -3.4028235E+38. They are stored as 32 bits (4 bytes) of information.
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</p>
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<p class='vspace'></p><p>Floats have only 6-7 decimal digits of precision. That means the total number of digits, not the number to the right of the decimal point. Unlike other platforms, where you can get more precision by using a double (e.g. up to 15 digits), on the Arduino, double is the same size as float.
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</p>
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<p class='vspace'></p><p>Floating point numbers are not exact, and may yield strange results when compared. For example <code>6.0 / 3.0</code> may not equal <code>2.0</code>. You should instead check that the absolute value of the difference between the numbers is less than some small number.
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</p>
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<p class='vspace'></p><p>Floating point math is also much slower than integer math in performing calculations, so should be avoided if, for example, a loop has to run at top speed for a critical timing function. Programmers often go to some lengths to convert floating point calculations to integer math to increase speed.
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</p>
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<p class='vspace'></p><h4>Examples</h4>
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<pre> float myfloat;
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float sensorCalbrate = 1.117;
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</pre>
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<p class='vspace'></p><h4>Syntax</h4>
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<pre> float var = val;
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</pre>
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<p class='vspace'></p><ul><li>var - your float variable name
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</li><li>val - the value you assign to that variable
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</li></ul><p class='vspace'></p><h4>Example Code</h4>
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<pre>
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int x;
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int y;
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float z;
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x = 1;
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y = x / 2; // y now contains 0, ints can't hold fractions
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z = (float)x / 2.0; // z now contains .5 (you have to use 2.0, not 2)
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</pre>
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<p class='vspace'></p><h4>See Also</h4>
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<ul><li><a class='wikilink' href='Int.html'>int</a>
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</li><li><a class='wikilink' href='Double.html'>double</a>
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</li><li><a class='urllink' href='VariableDeclaration.html' rel='nofollow'>Variable Declaration</a>
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</li></ul><p class='vspace'></p><p><a class='wikilink' href='index.html'>Reference Home</a>
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</p>
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<p class='vspace'></p><p><em>Corrections, suggestions, and new documentation should be posted to the <a class='urllink' href='http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?board=swbugs' rel='nofollow'>Forum</a>.</em>
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</p>
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<p class='vspace'></p><p>The text of the Arduino reference is licensed under a
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<a class='urllink' href='http://creativecommons.org/licenses/by-sa/3.0/' rel='nofollow'>Creative Commons Attribution-ShareAlike 3.0 License</a>. Code samples in the reference are released into the public domain.
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