N的阶乘计算-高精度乘法,每个数据单元存4位,每次计算4位而非一位,比一般一位为单元的高精度算法约快4倍-Calculation of the factorial N- High-precision multiplication, each data unit 4 deposit for each calculation of four instead of one, than a high-precision algorithm for the unit about 4 times faste