As we move towards ultrascale computing, computer architecture is bound to see dramatic changes. Multiple nodes, with or without shared memory, multicore and accelerators (GPUs, FPGAs) will be the norm. For many problems, such as finite difference numerical simulations, the array used to represent a perfect match between the user level code and the hardware architecture’s uniform memory access. Arrays, and to some extent multiarrays, are well supported by most programming languages. A standard compiler maps the array for uniform memory. Some programming models, such as partitioned global address space, allows mapping an array across distributed, yet for each partition, uniform memory. For ultrascale architectures, the simple mapping between user level (multi)array and distributed, non-uniform memory, will disappear. Here we propose an API for arrays, empowering the software developer to implement their own array-memory layout. Application code written towards the API will be independent of underlying architecture changes, thus easily ported to new architectures as they evolve.