#include <graphics.h>
void setvisualpage(int page);
 

setvisualpage makes page the visual graphics page.

/* setvisualpage example */
 
#include <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <conio.h>
 
int main(void)
{
   /* select driver and mode that supports multiple pages */
   int gdriver = EGA, gmode = EGAHI, errorcode;
   int x, y, ht;
 
   /* initialize graphics and local variables */
   initgraph(&gdriver, &gmode, "");
 
   /* read result of initialization */
   errorcode = graphresult();
   if (errorcode != grOk)    /* an error occurred */
   {
printf("Graphics error: %s\n", grapherrormsg(errorcode));
 
printf("Press any key to halt:");
getch();
exit(1);   /* terminate with an error code */
   }
 
   x = getmaxx() / 2;
   y = getmaxy() / 2;
   ht = textheight("W");
 
   /*  select the off screen page for drawing */
   setactivepage(1);
 
   /* draw a line on page #1 */
   line(0, 0, getmaxx(), getmaxy());
 
   /* output a message on page #1 */
   settextjustify(CENTER_TEXT, CENTER_TEXT);
   outtextxy(x, y, "This is page #1:");
   outtextxy(x, y+ht, "Press any key to halt:");
 
 
   /* select drawing to page #0 */
   setactivepage(0);
 
   /* output a message  on page #0 */
   outtextxy(x, y, "This is page #0.");
   outtextxy(x, y+ht, "Press any key to view page #1:");
   getch();
 
   /* select page #1 as the visible page */
   setvisualpage(1);
 
   /* clean up */
   getch();
   closegraph();
   return 0;
}

graphresult setactivepage swapbuffers

  no output of example at the moment
  do not hesitate and add it...