I am trying to make an algorithm that draws lines. I am trying create a bitmap that the line will be written to and then load that bitmap to the screen. The only thing I do not know is how to make the line be written to the bitmap. I know how to create load bitmaps that are pictures but I have trouble with making a bitmap that is created using a drawing function.

I meant writing a drawing to a bitmap, I know how to define bitmaps and load pictures into them but I do not know to load products of real-time drawing functions into them.

You actually have to draw onto a bitmap. For example, drawing a line goes like this:

BITMAP *bmp = create_bitmap(320, 200);
line(bmp, 0, 0, 319, 199, makecol(255, 255, 255));

If by 'real-time' you mean to move a line onto a bitmap, then you have to draw it and erase it in every loop, using xor mode:

BITMAP *bmp = create_bitmap(320, 200);
int x = 0;
int y = 0;
xor_mode(true);
line(bmp, x, y, x + 319, y + 199, makecol(255, 255, 255));
while (loop) {
    line(bmp, x, y, x + 319, y + 199, makecol(255, 255, 255));
    x++;
    line(bmp, x, y, x + 319, y + 199, makecol(255, 255, 255));
    readkey();
}

xor mode draws stuff in such a way that the 2nd time a picture is drawn (in the same position as in the first time), it is erased.

cough RTFM cough, but yes, you got it.

Yeah, because the documentation for line() only says that the first parameter is the BITMAP that the line will be drawn too.

What I'm saying is there is no section that generally describes this sort of concept. If he really wanted to learn from the manual he would have to read tons and tons of functions' documentation (most of which he would not even understand) until he just happened to come across some useful information. The whole process would probably take him a week and he would just give up.

Its a conceptual question, not a syntactical one. Therefore I believe it is totally valid and the phrase "RTFM" is out of place.

He asked the question after he was given example code that demonstrated this, though. It would have been quicker for him to confirm this by looking at the manual than it was for him to post that question. Also, I'd consider TFM to include the allegro examples, since in many cases they are as good/better than the manual. Maybe I should have said RTFMOLATFAE.