函数名: setgraphbufsize 
 功  能: 改变内部图形缓冲区的大小 
 用  法: #include <graphics.h> 
         unsigned far setgraphbufsize(unsigned bufsize); 
 程序例: 
#include <graphics.h> 
 #include <stdlib.h> 
 #include <stdio.h> 
 #include <conio.h> 
#define BUFSIZE 1000 /* internal graphics buffer size */
int main(void) 
 { 
    /* request auto detection */ 
    int gdriver = DETECT, gmode, errorcode; 
    int x, y, oldsize; 
    char msg[80]; 
   /* set the size of the internal graphics buffer */ 
    /* before making a call to initgraph.           */ 
    oldsize = setgraphbufsize(BUFSIZE); 
   /* 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; 
   /* output some messages */ 
    sprintf(msg, "Graphics buffer size: %d", BUFSIZE); 
    settextjustify(CENTER_TEXT, CENTER_TEXT); 
    outtextxy(x, y, msg); 
    sprintf(msg, "Old graphics buffer size: %d", oldsize); 
    outtextxy(x, y+textheight("W"), msg); 
   /* clean up */ 
    getch(); 
    closegraph(); 
    return 0; 
 }