How can now write some text on the screen with some color?
For example, how to write "Hello!" with blue background and white foreground color?
I've saw the int 10,09 function, how can I use it in very simple way?

Thanks a lot!!

From the old kelvar example:

It worked!! Thanks!! But how to know the color number to put on bl?
I mean how to how the number of red, blue, yellow...,red on blue, white on red....
Thanks

there are 2 colors: foreground (in low order 4 bits) and background (in high order 4 bits). Each 4 bits escribe color like this:
0: red
1: green
2: blue
3: add light
so, for example 0001b is red, 0010b is green, 0011b is red + green etc. But i think it is easier to remember these 16 colors. and then just combine values in bl:

This can be also described this way: the four-bit values for colors are as following (the highest bit is the brightness bit, so to get the value of light red you add value of red to 8, getting 0Ch, etc.):

Normal:
0 black
1 blue
2 green
3 cyan
4 red
5 magenta
6 brown
7 light gray

Bright:
8 dark gray
9 light blue
A light green
B light cyan
C light red
D light magenta
E yellow
F white

The pair 6 and 0Eh of colors is a small exception, where bright color has a bit different hue that the normal one.

To get the attribute for a character (the byte that you pass to the function 9 of interrupt 10h, or write directly into screen memory), you put the color for a background into the high nibble, and color for the text into the low nibble of byte value.
For example 1Bh is the light cyan text on the blue background and 7Fh is white text on the light gray background.

But there are few more tricks about the attributes - first, the brightess bit in the nibble describing the color for the background may have different meaning (and it has by default) - it makes the character blink instead of making the backround color brigther. So depending of the current setting 9Fh may mean white text on the light blue background, or blinking white text on the normal blue background. You can toogle this setting with function 1003h of interrupt 10h. Pass BX=0 to that function to enable background brightening, or BX=1 to enable blinking.

And the last, a bit less well-known trick is that on the VGA you can enable highest bit of low nibble (the one describing text color) to choose one of the two character sets instead of brigthening the text color. This way you can use two different fonts at the same time in text mode. This one is a bit more tricky, you do it with 11xxh functions.

Also there is alternative way, by using ANSI escape sequences (control codes) with DOS (Int21h) functions. But it requires that ANSI driver (ansi.sys on MS-DOS, nansi.sys on FreeDOS) is loaded.

http://www.delmar.edu/Courses/CIS415L/ANSIsys.htm - here is list of DOS ANSI sequences.

Thanks, it's working... but how can I clean the screen paint it with blue, for example (I don't want the black background)?

Thanks!!

In DOS, you can write directly to video ram screen buffer.
It is *usually* located at segment B800.
Here follows 2D array that describes screen
array[1..y] of array [1..x] of word
where word (2 bytes) describes one character. first byte is character ASCII code and second is color. So clearing screen could be:

i just don't remember how to get "x" and "y", i think there is some BIOS procedure for it.

I isn't working... and I don't want to write directly to video ram buffer... Can't use interrupt to do it?

You can do it this way:


You can look up all the VGA functions in the Ralph Brown's Interrupt List.

Thanks Privalov!! It worked allright!!

Well, it's basically only in two places - segment B800 (for CGA and compatible adapters in text mode) or B000 (for MDA and compatible adapters). So, you simply need to detect MDA (for example, using BIOS equipment word), and use B000 instead of B800 if adapter is MDA.

Hey i have some code to help you out !
You can find it here http://board.flatassembler.net/topic.php?t=1806
Don't worry it's working very well but i want to improve it so i need some help, but that should allow you to print text anywhere on the screen, with any combination of backgroun/foreground color, and the strings can be long as u want ( almost ) and don't have to be terminated by a character like '0' or '$'

you might want to see this topic:

http://board.flatassembler.net/topic.php?t=2186

MATRIX