Thanks.
The code is found on tutorial manual also.
And it's perfect it contains the essential.

I done that code for beginning:

function camera_follow(ENTITY* ent)
{
var distance_to_player = -300 ;
var cam_X_offset = 10 ;
var cam_Height = 200 ;
while(1) {
vec_set(camera.x,vector(distance_to_player,cam_X_offset,cam_Height));
vec_rotate(camera.x,ent.pan);
vec_add(camera.x,ent.x);
vec_set(camera.pan,vector(ent.pan,-10,0));
wait(1);
}
}

As the game progresses, i will make it better.