The FOR statement is a looping statement that repeats  execution
  of  a  statement  according  to the value of a control variable.
  The control variable assumes a value within a specified range or
  set.  A FOR statement has one of the following forms:

     FOR control-variable := initial {TO | DOWNTO} final-value DO
        statement

     FOR control-variable IN set-expression DO
        statement

  The 'control-variable' is the  name  of  a  previously  declared
  variable of an ordinal type.

  The 'initial-value' and 'final-value' are expressions that  form
  a range and whose type is assignment compatible with the type of
  the control variable.

  The 'set-expression' is an expression resulting in  a  value  of
  SET  type.   The  base  type  of  the  set  must  be  assignment
  compatible with the control variable.

  The 'statement' is any VSI Pascal statement that does not change
  the value of the control variable.

  At run time, the initial and final values or the set  expression
  is evaluated before the loop body is executed.

  The 'TO | DOWNTO' directives determine  whether  loop  iteration
  will be incremental or decremental, respectively.

  In the TO form, VSI Pascal checks to see if  the  value  of  the
  control  variable  is less than or equal to the final value.  If
  this condition is met, the control variable takes on  the  value
  of  the  initial  value  for  the  first loop iteration.  During
  iterations, the control variable  increments  according  to  its
  data  type.  Looping ceases when the control variable is greater
  than the final value.

  In the DOWNTO form, VSI Pascal checks to see if the value of the
  control  variable  is  greater than or equal to the final value.
  If this condition is met, the  control  variable  takes  on  the
  value of the initial value for the first loop iteration.  During
  iterations, the control variable  decrements  according  to  its
  data  type.   Looping  ceases  when the control variable is less
  than the final value.

  In the set expression form, VSI Pascal checks to see if the  set
  expression  is not the empty set.  If this condition is met, the
  control variable takes on the value of one of the members of the
  set.  Iterations occur for each member of the set; the selection
  order of members of the set is undefined.  Looping  stops  after
  the loop body executes for each member of the set.

  In both the TO and  the  DOWNTO  forms,  incrementation  of  the
  control  variable  depends  on  its  type.   For example, values
  expressed in type INTEGER increment or decrement in units of  1.
  Values   expressed  in  type  CHAR  increment  or  decrement  in
  accordance with the ASCII collating sequence.

  After normal termination  of  the  FOR  statement,  the  control
  variable  does  not retain a value.  You must assign a new value
  to this variable before you use it elsewhere in the program.  If
  the  FOR  loop  terminates  with  a  GOTO statement, the control
  variable retains the last assigned value.  In this case, you can
  use the variable again without assigning a new value.

1  –  Examples

  Example:

      FOR I := 1 TO 10 DO
        FOR J := 1 TO 10 DO
           A[I,J] := 0;

  This example shows how you can nest FOR loops.  For  each  value
  of  I,  the executing program steps through all 10 values of the
  array J and assigns the value 0 to each component.

  Example:

     FOR I IN Set 1 DO
        Set2 := Set2 + [I + 1];

  This example shows a FOR-IN statement.   Set2  is  assigned  the
  successor of each value in Set1.