POS forces the field (of a  packed  or  unpacked  record)  to  a
  specific bit position within the record.

  Syntax:

     POS( n )

  The constant expression 'n' specifies the bit location, relative
  to the beginning of the record, at which the field begins.

  See the "HP Pascal Language Reference Manual" for  the  complete
  description of using the POS attribute.