ASYNCHRONOUS

 The ASYNCHRONOUS attribute  indicates  that  a  routine  may  be
 called  by  an asynchronous event (such as a condition handler).
 Since such an event can alter the values of variables within the
 routine  upredictably,  this  attribute  forces  the  routine to
 reference only local variables or variables  declared  with  the
 VOLATILE attribute.

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