EXECUTE:looping

1_example

 The variable j below will be made into a scalar:
 ...         !   
 DO j = x    ! x must be a vector, loop will execute len(x) times with
  ...        ! j successively taking on the value of each element of x
 ENDDO       !
 ...         !

2_example

 ...              !
 DO I = [2:20:4]  ! the loop will execute 5 times
  ...             !
 ENDDO            !
 ...              !

3_example

 ...
 X = [1;3;5;7;9;10;12;14]
 DO I = X^2  ! the loop will execute LEN(X)=8 times with
  ...        ! I taking on the values [1;9;25;49;81;100;144;196]
 ENDDO 
 ...