Sinclair QL - Displaying Bitmaps & Text

Direct video memory

Video memory starts at 0x20000

In Mode 4 (512×256 4 colour) the memory is laid out in byte pairs (or words)

Red byte        | Green byte
0 0 0 0 0 0 0 0 | 0 0 0 0 0 0 0 0

Those 16 bits set a series of 8 contiguous horizontal pixels. The values of the Red and Green byte are AND-ed to get the final colour:

Red | Green | Result
1   | 0     | Red
0   | 1     | Green
1   | 1     | White
0   | 0     | Black

Example 1:

0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1

…would draw an 8 pixel horizontal line in Red.

Example 2:

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

…would draw an 8 pixel horizontal line in White.