C Program of surfaces using lines and colors

#include<graphics.h> 
#include<conio.h> 
#include<dos.h> 
#include<alloc.h> 
#include<math.h> 
void main() 
{ 
int gm, gd=DETECT; 
initgraph(&gd,&gm,””); 
setviewport(100,100,300,300,0); 
for(j=0;j<200;j=j+20) 
{ 
for(i=0;i<=200;++i) 
{ 
if (i%20==0) 
setcolor(rand()%16+1); 
line(i,j,i,j+20); 
} 
delay(100); 
} 
getch(); 
}