AH = 0C AL = color value (XOR'ED with current pixel if bit 7=1) BH = page number, see VIDEO PAGES CX = column number (zero based) DX = row number (zero based) returns nothing - if bit 7 is 1, color specified is XOR'ed with current pixel - page number in BH ignored for 320x200 4 color graphics mode - this function is known to destroy AX and possibly SI and DI on on some PS/2 VGA systems