FOR

        [SIC\]FOR Loop_Variable n1 n2 n3 TO n4 BY n5 n6 TO n7
        or
        [SIC\]FOR /WHILE Logical_Expression

    Open  a  FOR-NEXT  loop to be executed for values in the list (FOR Vari-
    able), or until a logical expression becomes false  (FOR  /WHILE).   The
    last  character of the prompt becomes a ':' instead of '>', and all sub-
    sequent commands typed in until NEXT are the body of  the  loop.  Up  to
    nine  loops may be nested in any way. The index of the loop will be sub-
    stituted to the loop variable Loop_Variable during loop  execution.  The
    substitution  occurs  also within character strings if the loop variable
    name is included between single quotes. Note that the index  values  may
    be real.

        [SIC\]FOR Loop_Variable n1 n2 n3 TO n4 BY n5 n6 TO n7

    The loop specified in this example will execute for the following values
    of the index :
            n1
            n2
            n3, n3 + n5, n3 + 2 n5, n3 + 3 n5, ... , n4
            n6, n6 + 1, n6 + 2, ... , n7
    (assuming that n4-n3 is a multiple of n5, n7-n6 an integer).  Loop vari-
    ables  are  undefined  outside  the loop, and must not be previously de-
    fined. Invalid ranges are ignored at execution time: e.g. in the  previ-
    ous  example,  the  loop  would  not  be  executed for n3 TO n4 BY n5 if
    n5*(n4-n3) < 0, but no error is signaled. Increments of 0 produce an er-
    ror.

    Conditional  loops  execute  until the logical expression becomes false.
    For example FOR /WHILE .TRUE. will execute forever.