Color Text Mode
There 8 pages in the address space B8000h~ BFFFFh
It’s most popular that the monitor shows the page 0.
One page shows 80*25 characters, each character use 2 bytes
Character layout
| Byte |
Description |
| 0 |
the ASCII code |
| 1 |
the control code |
Control code
| Bit |
Description |
| 0 |
Front B |
| 1 |
Front G |
| 2 |
Front R |
| 3 |
Highlight |
| 4 |
Back B |
| 5 |
Back G |
| 6 |
Back R |
| 7 |
Blink |
Underline
The Underline is controlled by VGA register 14 and 15. The PC system use port 0x3d4 and 0x3d4 VGA registers
0x3d4 is the index regiser and 0x3d4 is the data register.
For instance, to write value to VGA registers 14
out 0x3d4, 14
out 0x3d5, value
| Reg |
Description |
| 14 |
Underline Position X |
| 15 |
Underline Position Y |
