while(!done)
{
for(t=0;t<n*2*3.14;t+=0.01)
{
ALLEGRO_EVENT events;
al_wait_for_event(event_queue,&events);
if(events.type==ALLEGRO_EVENT_DISPLAY_CLOSE)
{
done=true;
}
else if(events.type==ALLEGRO_EVENT_TIMER)
{

x=100*cos(t) + 400;
y=100*sin(t) + 400;
al_draw_filled_circle(x,y,5,al_map_rgb(100,200,100));
al_draw_filled_circle(400,400,15,al_map_rgb(500,200,100));

al_flip_display();
al_clear_to_color(al_map_rgb(0,0,0));
n++;
}

}
}
what am i doing wrong here .. i cant seem to close the display

This should make it clearer what is actually happening. You're incrementing n and the loop never ends.

for(t=0;t<n*2*3.14;t+=0.01)
{
//...
n++;
}

Yes, but he's using al_wait_for_event, which means that n gets incremented before t does, so it's an endless loop.

What you basically want to do with events is to handle all events currently in the queue, and then handle drawing separately. Separate logic and drawing.

For example, to change your code to work you just need to rearrange it a little.

I'm not entirely sure what you're doing with 'n' there. Because all it is doing is making it go around the circle 'n' times, but once is enough.

An event is basically the computer telling you "hey! Something just happened!". Now when you register events, you are telling the computer "let me know if something happens with this!" so you register a timer which fires off however often you set it to, so that will now trigger an event. Then you register your keyboard and mouse so they trigger events. Now when a timer comes up, or a keyboard or mouse is pressed or moved, it triggers an event. These events are added to an event queue (a list of events that happened). You have some code that waits for an event to happen (waits for someone to press a key, move a mouse or the timer to fire off that might be for updating the screen). When an event is triggered, you then ask allegro, hey, what event was that? And you have some code that says if it was the keyboard, then we'll go into this block of code and check which keys were pressed and respond accordingly. The same goes for the other events.

That's about as well as I can explain it.

One additional note. When you post your program code, it helps us all if you put

<code>

before it and

</code>

after it. So when you post it you see...

<code>
if(a==b) {
   c--;
}
</code>

and we see this...

if(a==b) {
   c--;
}

It looks better and is easier for us to help you.

note: I almost typed c++ in the above example but realized that would look too ugly!