The text mode video screen in the PC is memory-mapped to physical address
0xb0000 on monochrome adapters and 0xb8000 on color adapters.
(Our PCs all have color adapters, and most likely any machine you find will
too. I merely include the monochrome adapter information for completeness).
You can access a specific physical address in the PC by merely assigning
it to a pointer, and then treating the pointer as a reference to an
array. Assigning a numeric value to a pointer is just a matter of using
a typecast:
char *vidmem = (char *) 0xb8000;
The text mode is 80 columns by 25 rows, with 2 bytes per character
that appears on the screen. The first byte is the ASCII value of
the character itself, and the second is the attribute byte. 0x07 is
white on black, and works fine. You may want to experiment with
other colors.
