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 <P>It&#146;s worth pointing out again that the bit mask operates on the data in the latches, not on the data in display memory. This makes the bit mask a flexible resource that with a little imagination can be used for some interesting purposes. For example, you could fill the latches with a solid background color (by writing the color somewhere in display memory, then reading that location to load the latches), and then use the Bit Mask register (or write mode 3, as we&#146;ll see later) as a mask through which to draw a foreground color stencilled into the background color <I>without</I> reading display memory first. This only works for writing whole bytes at a time (clipped bytes require the use of the bit mask; unfortunately, we&#146;re already using it for stencilling in this case), but it completely eliminates reading display memory and does foreground-plus-background drawing in one blurry-fast pass.</P>
-<TABLE WIDTH="100%"><TD VALIGN="TOP" WIDTH="5%" ALIGN="LEFT"><IMG SRC="images/25-01i.jpg"><TD VALIGN="TOP" ALIGN="LEFT" WIDTH="95%"><SMALL><I>This last-described example is a good illustration of how I&#146;d suggest you approach the VGA: As a rich collection of hardware resources that can profitably be combined in some non-obvious ways. Don&#146;t let yourself be limited by the obvious applications for the latches, bit mask, write modes, read modes, map mask, ALUs, and set/reset circuitry. Instead, try to imagine how they could work together to perform whatever task you happen to need done at any given time. I&#146;ve made my code as much as four times faster by doing this, as the discussion of Mode X in Chapters 47&#150;49 demonstrates.</I></SMALL>
+<TABLE WIDTH="100%"><TD VALIGN="TOP" WIDTH="5%" ALIGN="LEFT"><IMG SRC="images/i.jpg"><TD VALIGN="TOP" ALIGN="LEFT" WIDTH="95%"><SMALL><I>This last-described example is a good illustration of how I&#146;d suggest you approach the VGA: As a rich collection of hardware resources that can profitably be combined in some non-obvious ways. Don&#146;t let yourself be limited by the obvious applications for the latches, bit mask, write modes, read modes, map mask, ALUs, and set/reset circuitry. Instead, try to imagine how they could work together to perform whatever task you happen to need done at any given time. I&#146;ve made my code as much as four times faster by doing this, as the discussion of Mode X in Chapters 47&#150;49 demonstrates.</I></SMALL>
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 <P>The example code in Listing 25.1 is designed to illustrate the use of the Data Rotate and Bit Mask registers, and is not as fast or as complete as it might be. The case where text <I>is</I> byte-aligned could be detected and performed much faster, without the use of the Bit Mask or Data Rotate registers and with only one display memory access per font byte (to write the font byte), rather than four (to read display memory and write the font byte to each of the two bytes the character spans). Likewise, non-aligned text drawing could be streamlined to one display memory access per byte by having the CPU rotate and combine the font data directly, rather than setting up the VGA&#146;s hardware to do it. (Listing 25.1 was designed to illustrate VGA data rotation and bit masking rather than the fastest way to draw text. We&#146;ll see faster text-drawing code soon.) One excellent rule of thumb is to minimize display memory accesses of all types, especially reads, which tend to be considerably slower than writes. Also, in Listing 25.1 it would be faster to use a table lookup to calculate the bit masks for the two halves of each character rather than the shifts used in the example.</P>
 <P>For another (and more complex) example of drawing bit-mapped text on the VGA, see John Cockerham&#146;s article, &#147;Pixel Alignment of EGA Fonts,&#148; <I>PC Tech Journal</I>, January, 1987. Parenthetically, I&#146;d like to pass along John&#146;s comment about the VGA: &#147;When programming the VGA, <I>everything</I> is complex.&#148;</P>