15.64.31.21  WRAP   - If  WRAP  is  on then when you SET HIST NEXT and the
current histogram is the last one, the histogram number will  wrap  around
to  the first number.  Similarly SET HIST PREVIOUS will wrap around to the
last one.  If you specify WRAP=OFF then you will  get  a  warning  message
instead  of  wrapping.   If  you  omit  ON  or OFF then ON is assumed.  By
default WRAP is ON when TOPDRAWER is used interactively, but OFF  when  it
is used in a batch stream.