SVGALib
SVGAlib was an open-source low-level graphics library which ran on Linux and FreeBSD and allowed programs to change video mode and display full-screen graphics. Some popular games like Quake and Doom have been ported to use SVGAlib.

History
The library was popular in mid-1990s. Toward 2000, many applications that used it migrated to X11 and SDL, which itself can make use of SVGAlib as a video driver.

Sample
A sample of SVGAlib code is shown below:
#include <stdlib.h>
#include <unistd.h>
#include <vga.h>

int main(void)
{
   int color = 4;
   int x = 10;
   int y = 10;
   unsigned int seconds = 5;

   /* detect the chipset and give up supervisor rights */
   if (vga_init() < 0)
        return EXIT_FAILURE;

   vga_setmode(G320x200x256);
   vga_setcolor(color);
   vga_drawpixel(x, y);

   sleep(seconds);

   /* restore textmode and fall back to ordinary text console handling */
   vga_setmode(TEXT);

   return EXIT_SUCCESS;
}

See also

 DirectFB
 General Graphics Interface (GGI)
 Linux framebuffer

External links
 SVGAlib
 Development versions (link on the site itself is broken)
 svgalib windows

Articles with example C code
Free computer libraries
Graphics libraries