函数名: bar 
 功  能: 画一个二维条形图 
 用  法: #include <graphics.h> 
         void far bar(int left, int top, int right, int bottom); 
 程序例: 
#include <graphics.h> 
 #include <stdlib.h> 
 #include <stdio.h> 
 #include <conio.h> 
int main(void) 
 { 
    /* request auto detection */ 
    int gdriver = DETECT, gmode, errorcode; 
    int midx, midy, i; 
   /* 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; 
   /* loop through the fill patterns */ 
    for (i=SOLID_FILL; i<USER_FILL; i++) 
    { 
       /* set the fill style */ 
       setfillstyle(i, getmaxcolor()); 
      /* draw the bar */ 
       bar(midx-50, midy-50, midx+50, 
          midy+50); 
      getch(); 
    } 
   /* clean up */ 
    closegraph(); 
    return 0; 
 }