Editing ATASCII (section)

===Inverse video===
ATASCII only has 128 unique graphic characters, with the upper 128 graphic characters (index 128 to 255) being [[inverse video]] variants of the lower 128 graphic characters (index 0 to 127). If the high-order bit is set on a character (i.e., if the byte value of the character is between 128 and 255), the character is generally rendered as the inverse video variant of its counterpart between 0 and 127, using a bitwise negation of the character's glyph. This is done by the [[ANTIC]] chip.

Due to this behavior, there is asymmetry in the selection of block-drawing characters. In normal video, there are lower triangles but no upper triangles, a left half block but no right half block, and a lower half block but no upper half block; these ostensibly missing characters can be displayed by using inverse video.