text: #include <stdlib.h>
  #include <stdio.h>
  
  int main(void)
  {
    const int dimx = 800, dimy = 800;
    int i, j;
    FILE *fp = fopen("first.ppm", "wb"); /* b - binary mode */
    (void) fprintf(fp, "P6\n%d %d\n255\n", dimx, dimy);
    for (j = 0; j < dimy; ++j)
    {
      for (i = 0; i < dimx; ++i)
      {
        static unsigned char color[3];
        color[0] = i % 256;  /* red */
        color[1] = j % 256;  /* green */
        color[2] = (i * j) % 256;  /* blue */
        (void) fwrite(color, 1, 3, fp);
      }
    }
    (void) fclose(fp);
    return EXIT_SUCCESS;
  }
  