The Finite$-$Difference Time$-$Domain $($FDTD$)$ method is a computational electromagnetic tech$-$

nique for solving for the electric and magnetic fields in arbitrary spatial domains in the time

domain. In contrast to techniques such as the Finite Element Method $($FEM$)$ and the Method of

Moments $($MoM$),$ this technique is straightforward to understand and is simple to program. A

rudimentary $2$D TM z code is included in Section $7$ and is used to illustrate the main features

of the method.