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BIOS int 0x10 ah=0xa (print char in cursor position in teletype mode) can be used also in graphics mode.
In: AL=char, BH=page(only in text mode), BL=char color(only in graphics mode). I tried it in VGA 320x200x8 mode and it prints on black background. How can I change background color? I tried to pass bgcolor in BH (somewhere I saw this variant) - the same black. I tried to use ah=0xb bh=0x00 bl=bgcolor - the same black. Any other variants? I can steal font from VGA memory before I switch to graphics mode and do it by hand, but may be this can be solved easier? And what about transparent bgcolor?
It's my misprint: int 0x10 ah=0xe - write char in teletype mode and int 0x10 ah=0x9 - write char. Ralf Int List says about foreground color in BL but what about background? P.S: I hate Ralf Int List - there are too many notes about concrete PC model.
Wikipedia only lists functions that are supported by the IBM 5150 BIOS. Mode 0x13 was added with IBM's VGA, and printing text with a background color in mode 0x13 may have come later.
On the three machines I tried both AH=0x09 and AH=0x0A used BH as the background color. What are you using that doesn't support this extension?