Homogeneous cluster architectures dominating high-performance computing (HPC) today are challenged, in particular when thinking about reaching Exascale by the end of the decade, by heterogeneous approaches utilizing accelerator elements. The DEEP (Dynamical Exascale Entry Platform) project aims for implementing a novel architecture for high-performance computing consisting of two components - a standard HPC Cluster and a cluster of many-core processors called Booster. In order to make the adaptation of application codes to this Cluster-Booster architecture as seamless as possible, DEEP provides a complete programming environment. It integrates the offloading functionality given by the MPI standard with an abstraction layer based on the task-based OmpSs programming paradigm. This paper presents the DEEP project with an emphasis on the DEEP programming environment.