Display pixel on screen in C

How would I change a pixel on a display, in C?

Assume NOTHING: I am using a linux machine from console to do this. I do not want to use GUI toolkits or frameworks to draw the pixel. I do not want to draw the pixel in a window. I want to draw the pixel directly to the screen.

EDIT: I have a screen. I'm on a laptop running linux from console. I'd prefer a solution not using X as I'd rather learn how X works than how to use X.

If theres more information, ask, but don't开发者_如何学运维 assume. I'm not trying to build a GUI, and that was the main purpose of blocking assumptions as I don't want people to assume I'm doing things the long way when in reality I'm just tinkering.

EDIT 2: You may use any X11 related libraries provided that you can explain how they work.

If we really assume nothing, can we even assume that X is running? For that matter, can we even assume that there is a video card? Perhaps Linux is running headless and we're accessing it over a serial console.

If we are allowed to assume a few things, let's assume that Linux has booted with framebuffer support. (It's been a couple years since I worked with Linux framebuffers, I may get some of the details wrong.) There will be a device created, probably /dev/fb or /dev/fb0. Open that file and start writing RGB values at an offset, and the screen will change, pretty much regardless of anything: text console, graphical console, full-fledged desktop envrionment, etc. If you want to see if framebuffer support is working, do dd if=/dev/zero of=/dev/fb on the command line, and the display should go all black.

C doesnt have any graphics capabilities - you'd need to use a third party library for this.

You cannot assume a display in C. There is literally no way to do what you ask.

Edit: Okay, you have a display, but again, there's not a whole lot you can get from there. The point is that there are a TON of competing standards for graphics displays, and while some of them (VGA interfaces, for example) are standardized, a lot of the others (display driver interfaces, for example) are NOT. Much of what X (and other display device drivers, such as Windows or the like) do, is have specific interface code for how to talk to the display drivers; they abstract out the complexity of dealing with the display drivers. The windowing systems, though, have HUGE libraries of complicated and specific code for dealing with the display drivers; the fact that these things are relatively transparent is an indication of just how much work they've put into these things over time.

Very primitive and making a lot of assumptions:

fd = open("/dev/fb0", O_RDWR);
lseek(fd, 640*y+x, SEEK_SET);
write(fd, "\377\377\377\377", 4);

In reality, you would use mmap rather than write, and use the appropriate ioctl to query the screen mode rather than assuming 640xHHH 32bpp. There are also endian issues, etc.

So in real reality, you might use some sort of library code that handles this kind of thing for you.

I suppose you could paint to the terminal program that you are using as your console. All you have to do is figure out which one that is and look it up.

Whoops I assumed a terminal. :P

I think what you are looking for is information on how to write to the frame buffer. The easiest way would be to use SDL and render to the frame buffer, or else use GTK+ with DirectFB, although that goes against your edict on not using toolkits or frameworks.