写了一个程序名为Get_frequencies是构造一个字频表。输入

该过程应该是一个指向字符串的指针和指向256的双数组初始化

为全零。每个阵列位置是由对应的ASCII码索引。当过程

返回时，阵列中的每个条目都包含了多少次的计数对应

字符发生在字符串中。-Write a procedure named Get_frequencies that constructs a character frequency table. Input to

　the procedure should be a pointer to a string and a pointer to an array of 256 doublewords initialized

　to all zeros. Each array position is indexed by its corresponding ASCII code. When the procedure

　returns, each entry in the array contains a count of how many times the corresponding

　character occurred in the string.