Stars is a classic forth example in which for a height of 20 lines, it draws 40 stars wide, and for each x y % 0 = draws a star, it should look like this:

****************************************
 * * * * * * * * * * * * * * * * * * * *
  *  *  *  *  *  *  *  *  *  *  *  *  * 
   *   *   *   *   *   *   *   *   *   *
    *    *    *    *    *    *    *    *
     *     *     *     *     *     *    
      *      *      *      *      *     
       *       *       *       *       *
        *        *        *        *    
         *         *         *         *
          *          *          *       
           *           *           *    
            *            *            * 
             *             *            
              *              *          
               *               *        
                *                *      
                 *                 *    
                  *                  *  
                   *                   *

Uxntal

|0100 ( -> )
    #1501
    &for-i ( limit i -- )
        STHk #2901
        &for-j ( limit j -- )
            DUP STHkr DIVk MUL SUB
            #202a ROT ?{ SWP } POP #18 DEO
            INC GTHk ?&for-j
        POP2 POPr
        #0a18 DEO
        INC GTHk ?&for-i
    POP2
BRK

Factor

: draw-stars ( -- )
    20 [1..b] [ 
       40 [1..b] swap '[ 
          _ divisor? "*" " " ? write
       ] each nl
    ] each ;