设置可见图形页号

[c]代码库

#include <graphics.h> 
#include <stdlib.h> 
#include <stdio.h> 
#include <conio.h> 

int main(void) 
{ 
   /* select a 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; 
}