The possibility of using self-assembled films of block polymers as templates to fabricate nanoscale structures for devices has attracted great attention towards this class of materials. We present a technique for mapping an experimental system to a bead spring model for the study of these systems with molecular simulations. By keeping only necessary details the mapping procedure turns into an estimation of few characteristic parameters which exactly represents a realistic block copolymer experiment. The beauty of this technique is that it is simple to apply and captures the behavior of the specific block copolymer systems under study. In our work this mapping technique is utilized in conjunction with a Monte Carlo (MC) algorithm to perform simulations on block copolymer systems and blends of block copolymer with its corresponding homopolymers. The microphase separation is investigated on unpatterned and patterned surfaces. Our results are in agreement with experiments and in addition our calculations give a molecular level insight in the distribution of the chains providing an explanation for the observed structures.