In this paper we present an optimized implementation of finite difference time domain (FDTD) based simulation environment for electromagnetic (EM) analysis. The implementation is central processing unit (CPU) based. The optimisation is performed by introducing data structures, by multiple employment of the previously calculated elements and by intensive use of indexing tables. Comparison with conventional FDTD algorithm shows that a significant time saving can be realized. Also, the main features of graphical interface that are so far implemented in this simulation environment will be presented. [Projekat Ministarstva nauke Republike Srbije, br. TR-32051 i br. TR-33008]