说明：   算术编码是把一个信源表示为实轴上0和1之间的一个区间，信源集合中的每一个元素都用来缩短这个区间。 算术编码的过程如下： （1)设定编码区间的高段为h，编码区间的长度为g，EndC为编码字符分配的高段，StartC 为字符分配区间的低端。 （2)根据有限的信源估算出各元素的概率。 （3)杜宇编码的元素A1，根据（2）估算的概率和区间，计算出该元素编码后的新的l，和h。
(Arithmetic coding is a source expressed as a real axis between 0 and 1, a range of source collection of every element are used to shorten the interval. Arithmetic coding process is as follows: (1) set the encoding range for the high-paragraph h, the length of interval encoding g, EndC for encoding characters in the distribution of high-paragraph, StartC for the characters in the distribution of the low-end range. (2) According to the limited source to estimate the probability of each element. (3) Du coding element A1, according to (2) to estimate the probability and the interval to calculate the elements of the new code of l, and h.)