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0xb800 is the address of the framebuffer for text. Simply write characters to that address, using offset `((row * width) + col)` and they'll appear on screen.

In graphics mode it was, IIRC, 0xa000. I once wrote a pacman-type easter egg inside the point-of-sale system[1], because doing direct graphics straight to an address is so easy and simple.

[1] Was removed after pilot and before actual release.

In real mode addressing and graphic card in text mode, your video memory started at absolute address 0xb800:0x0000. It was an two-dimensional array, where you could poke and whatever you changed here, was reflected immediately on the display. Each element of the array was two bytes: character itself and color attributes.

I think it is also 0xb800 as it is a physical address; not ionly in real mode.

For physical linear address, it would be one digit (4-bits) longer (-> 0xb8000); when the segment:offset is combined, the result is 20-bit address.

Was not my point though.

Ok I think he’s referring to 0xB800, the VGA text buffer segment in real mode.

No not VGA, CGA actually