Abstract. The C++// language (pronounced C++ parallel) was designed and implemented with the aim of importing reusability into parallel and concurrent programming, in the framework of a mimd model. From a reduced set of rather simple primitives, comprehensive and versatile libraries are defined. In the absence of any syntactical extension, the C++// user writes standard C++ code. The libraries are themselves extensible by the final users, making C++// an open system. Two specific techniques to improve performances of a distributed object language such as C++// are then presented: Sharedon-Read and Overlapping of Communication and Computation. The appliance of those techniques is guided by the programmer at a very high-level of abstraction, so the additional work to yield those good performance improvements is kept to the minimum.Mathematics Subject Classification. 68N15, 68N19.