Like other Starlink subroutine libraries, PAR adheres throughout to the error-handling strategy described in SUN/104. Subroutines have an integer final argument called STATUS that is an inherited status, and will return without action unless the status is set to the value SAI__OK when they are invoked. (SAI__OK is a symbolic constant defined in the include file SAE_PAR.) This strategy greatly simplifies the coding since you can make a series of subroutine calls without having to check STATUS after each call; if an error occurs the subsequent routines do nothing. 1 Where necessary, PAR makes error reports through the ERR_ routines in the manner described in SUN/104, and therefore sets STATUS to a value other than SAI__OK.
1PAR_CANCL and PAR_UNSET are exceptions to this behaviour. Since they are freeing resources they attempt to work regardless of the inherited status.