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Retidy, removing align=left from headings and empty paragraphs

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James Gregory 2013-12-30 15:37:13 +11:00
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
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<center>
<table border="1">
<tr>
<td><a href="33-02.html">Previous</a></td>
<td>
<a href="33-02.html">Previous</a>
</td>
<td><a href="index.html">Table of Contents</a></td>
<td>
<a href="index.html">Table of Contents</a>
</td>
<td><a href="33-04.html">Next</a></td>
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<a href="33-04.html">Next</a>
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<p><br /></p>
<h4 align="left" id="Heading9">Setting the DAC</h4>
<h4 id="Heading9">Setting the DAC</h4>
<p>Like the palette RAM, the DAC registers can be set either directly or through the BIOS. Again, the BIOS should be used whenever possible, but there are a few complications here. My experience is that varying degrees of flicker and screen bounce occur on many VGAs when a large block of DAC registers is set through the BIOS. That&rsquo;s not a problem when the DAC is loaded just once and then left that way, as is the case in Listing 33.1, which we&rsquo;ll get to shortly, but it can be a serious problem when the color set is changed rapidly (&ldquo;cycled&rdquo;) to produce on-screen effects such as rippling colors. My (limited) experience is that it&rsquo;s necessary to program the DAC directly in order to cycle colors cleanly, although input from readers who have worked extensively with VGA color is welcome.</p>
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<p>This chapter has gotten about as big as a chapter really ought to be; the VGA color saga will continue in the next few. Quickly, then, Listing 33.1 is a simple example of setting the DAC that gives you a taste of the spectacular effects that color translation makes possible. There&rsquo;s nothing particularly complex about Listing 33.1; it just selects 256-color mode, fills the screen with one-pixel-wide concentric diamonds drawn with sequential attributes, and sets the DAC to produce a smooth gradient of each of the three primary colors and of a mix of red and blue. Run the program; I suspect you&rsquo;ll be surprised at the stunning display this short program produces. Clever color manipulation is perhaps the easiest way to produce truly eye-catching effects on the PC.</p>
<p><br /></p>
<center>
<table border="1">
<tr>
<td><a href="33-02.html">Previous</a></td>
<td>
<a href="33-02.html">Previous</a>
</td>
<td><a href="index.html">Table of Contents</a></td>
<td>
<a href="index.html">Table of Contents</a>
</td>
<td><a href="33-04.html">Next</a></td>
<td>
<a href="33-04.html">Next</a>
</td>
</tr>
</table>
</center>