Experiences in implementing Ada 9X protected records and requeue

Ada9x protected recorcfs provide an indirect communication method whereby tasks read and write the state of protected objects. The language ensures synchronisation by mutual exclusion for both readers and writers without the need for agent tasks (as was required in Ada83). This paper discusses an implementation of protected records in the York Ada Compiler Environ/nent (YACE)', together with thedifficulties that we~encounte~d, andhowthey we~overconle. Itconcludes with an evaluation of theimplementation, and some notes onthedistributed costs ofprotected records.