RSDFT is an ab-initio program with the real-space difference method and a pseudo-potential method. Using density functional theory (DFT), this calculates electronic states in a vast range of physical systems: crystals, interfaces, molecules, etc. RSDFT is suitable for highly parallel computing because it does not need the fast Fourier transformation. By using the K-computer, this program can calculate the electronic states of around 100,000 atoms. The Gordon Bell Prize for Peak-Performance was awarded to RSDFT in 2011.