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<h1 class="code">RANDOM</h1>
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<p style="text-align: right;"><a href="../ExampleTopics/RandomEx.htm" target="" title="" alt="" class="MCXref_0" xrefformat="{paratext}">RANDOM Examples</a>
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<p class="PlainText">Syntax: <span class="keyword_in_text">RANDOM</span> <![CDATA[ ]]><i>Variable</i></p>
<h2>Function</h2>
<p class="PlainText">Generate a pseudo-random number.
</p>
<ul>
<li value="1"><b><i>Variable</i></b> is a variable (usually a word) whose bits will be
scrambled to produce a random number. <i>Variable</i> acts as <span class="keyword_in_text">RANDOM</span>'s
input and its result output. Each pass through <span class="keyword_in_text">RANDOM</span> stores the next
number, in the pseudo-random sequence, in <i>Variable</i>.</li>
</ul>
<h2>Explanation</h2>
<p class="PlainText"><span class="keyword_in_text">RANDOM</span> generates pseudo-random numbers ranging from 0 to 65535. They're
called "pseudo-random" because they appear random, but are generated by a logic
operation that uses the initial value in <i>Variable</i> to "tap" into a sequence
of 65535 essentially random numbers. If the same initial value, called the "seed",
is always used, then the same sequence of numbers is generated. The following
example demonstrates this:</p>
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</p><pre class="BScode" xml:space="preserve">
SYMBOL result = W1
Main:
result = 11000 ' set initial "seed" value
RANDOM result ' generate random number
DEBUG result ' show the result on screen
GOTO Main
</pre>
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</p><pre class="BScode" xml:space="preserve">
result VAR Word
Main:
result = 11000 ' set initial "seed" value
RANDOM result ' generate random number
DEBUG DEC ? result ' show the result on screen
GOTO Main
</pre>
<p class="PlainText">In this example, the same number would appear on the screen over and over again.
This is because the same seed value was used each time; specifically, the first
line of the loop sets result to 11000. The <span class="keyword_in_text">RANDOM</span> command really needs
a different seed value each time. Moving the "Result =" line out of the loop will
solve this problem, as in:</p>
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<img src="../../graphics/bs1_inline.gif" border="0">
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</p><pre class="BScode" xml:space="preserve">
SYMBOL result = W1
Setup:
result = 11000 ' set initial "seed" value
Main:
RANDOM result ' generate random number
DEBUG result ' show the result on screen
GOTO Main
END
</pre>
<p>
<img src="../../graphics/bs2all_inline.gif" border="0">
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</p><pre class="BScode" xml:space="preserve">
result VAR Word
Setup:
result = 11000 ' set initial "seed" value
Main:
RANDOM result ' generate random number
DEBUG DEC ? result ' show the result on screen
GOTO Main
END
</pre>
<p class="PlainText">Here, result is only initialized once, before the loop. Each time through the
loop, the previous value of result, generated by <span class="keyword_in_text">RANDOM</span>, is used as the
next seed value. This generates a more desirable set of pseudo-random numbers.</p>
<p class="PlainText">In applications requiring more apparent randomness, it's necessary to "seed"
<span class="keyword_in_text">RANDOM</span> with a more random value every time. For instance, in the
example program, <span class="keyword_in_text">RANDOM</span> is executed continuously
(using the previous resulting number as the next seed value) while the program
waits for the user to press a button. Since the user can't control the timing of
button presses very accurately, the results approach true randomness. </p>
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<p style="text-align: right;">Copyright © <span class="ContactInfoCompanyName">Parallax Inc.</span></p>
<p style="text-align: right;"><span class="SystemShortDate">8/8/2012</span>
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