0xA000 is also the address of the memory location that holds the contents of the display in so-called "mode 13h" in the old IBM VGA displays.

Mode 13h was an extremely popular graphics mode, used by many PC games in the early 90s (probably also late 80s). It gave a resolution of 320x200 pixels with 8-bit colour palette.

After entering mode 13h, the way to plot a pixel is to poke the corresponding 8-bit memory address, where the 0th pixel (display top left) is 0xA000.