of memory from $400-$5FF and is a 32 character wide screen with 16 lines. The ROM character generator only holds 64 characters, so no lowercase characters are provided. "Lowercase" characters are rendered as uppercase with inverted color. On most CoCo generations it is green on very dark green. Semigraphics is a mode where alphanumerics and low resolution graphics can be mixed together. The 8th bit of a character determines if it is alphanumeric or treated as a 2×2 pixel grid. When the 8th bit is set, the next three bits determine the color and last 4 bits specify which quadrants of the character box are either the selected color or black. This allows a 64×32 graphics mode with 9 colors, the only mode where it is possible to display all 9 colors simultaneously. There are two colorsets. The default has black characters on a green background. The alternate has black characters on an orange background. The colorset selection does not affect semigraphics characters. The border is always black. The 6847 is capable of a Semigraphics 6 display mode, where two bits select a color and 6 bits determine which 1/6 of the character box is lit. Only 4 colors are possible, but the colorset bit of the VDG selects two groups of 4 colors. Only two colors are available in graphics blocks when using Semigraphics 6 on the CoCo. The default alphanumeric display for the CoCo is Semigraphics 4. Additional Semigraphics modes By setting the SAM such that it believes it is displaying a full graphics mode, but leaving the VDG in Alphanumeric/Semigraphics 4 mode, it is possible to subdivide the character box into smaller pieces. This creates the "virtual" modes Semigraphics 8, 12, and 24. In these modes it was possible to mix bits and pieces of different text characters as well as Semigraphics 4 characters. These modes were an interesting curiosity but not widely used, as the Semigraphics 24-screen consumed 6144 bytes of memory. These modes were not implemented on the CoCo 3. A programmer's reference manual for the CoCo states that due to a fire at Tandy's research lab, the papers relating to the semigraphics modes were shuffled, and so some of the semigraphics modes were never documented. CoCo enthusiasts created experimental programs to try to reverse engineer the modes, and were able to reconstruct the missing documentation. Bitmap modes Bitmap display modes are divided into two