实现一个6*6维的矩阵的相乘，并利用优化策略，使得程序的循环次数尽可能减少-To achieve a 6* 6-dimensional matrix multiplication, and using optimization strategy, so to minimize the number of iteration procedures

掌握求解离散时间系统差分方程的两种方法：迭代法和filter函数法。-Discrete-time control system differential equations to solve two methods: iteration and filter function method.