VMS Help PASCAL, Predeclared Routines, Low Level, OR_ATOMIC  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  The OR_ATOMIC function logically ORs the value of an  expression
  to the value of a variable, stores the newly computed value, and
  returns the previous value.

  Syntax:

    OR_ATOMIC(e,v)

  The type of the expression 'e'  must  be  assignment  compatbile
  with  that  of  the  variable  'v'.   The  variable v must be an
  INTEGER, UNSIGNED, INTEGER64, or UNSIGNED64 variable and must be
  allocated  on  a  natural boundary (ie, longword for INTEGER and
  UNSIGNED and quadword for INTEGER64 and UNSIGNED64).  The result
  of OR_ATOMIC is the same type as the variable 'v'.