可以将以bit为单位进行处理的算法扩展到8位，即以Byte为单位进行处理。由于有8个bit，所以有2^8种选择。这样明显会使运行时



间大为减少，速度明显更快，但是也有它的缺点，即，占用资源太大，所以综合考虑速度和 资源两点，采用半字节查表法。即以半



Byte为单位进行处理。由于有4个bit，所以有2^4种选择。-bit can be processed for the extension of the algorithm 8, to Byte unit for treatment. With 8 bit, it is 2 ^ 8 options. This will significantly reduce travel time significantly, significantly faster speed, but it also has its drawbacks, namely, taking up too much resources. Therefore, considering the speed and resources 2:00, semi-byte look-up table method. Byte is a semi-processed as a unit. As a four bit, it is 2 ^ 4 choice.