#include <graphics.h>
void cleardevice(void);
 

cleardevice erases (that is, fills with the current background color) the
entire graphics screen and moves the CP (current position) to home (0,0).

/* cleardevice example */
 
#include <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <conio.h>
 
int main(void)
{
   /* request autodetection */
   int gdriver = DETECT, gmode, errorcode;
   int midx, midy;
 
   /* 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 */
   }
 
   midx = getmaxx() / 2;
   midy = getmaxy() / 2;
   setcolor(getmaxcolor());
 
   /* for centering screen messages */
   settextjustify(CENTER_TEXT, CENTER_TEXT);
 
   /* output a message to the screen */
   outtextxy(midx, midy, "Press any key to clear the screen:");
 
   getch();   /* wait for a key */
   cleardevice();   /* clear the screen */
 
   /* output another message */
   outtextxy(midx, midy, "Press any key to quit:");
   /* clean up */
   getch();
   closegraph();
   return 0;
}

clearviewport

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