函数ReadDat()实现从文件ENG.IN中读取一篇英文文章，存入到字符串数组xx中；请编制函数encryptChar()，按给定的替代关系对数组xx中的所有字符进行替代，仍存入数组xx的对应的位置上，最后调用函数WriteDat()把结果xx输出到文件PS10.DAT中。

-ReadDat function () from a document ENG.IN read an article in English. credited to the string array xx; Please prepare encryptChar function (), according to the array of alternative relations xx of all characters for alternative still xx array deposited the corresponding position. Finally function call WriteDat () results xx output to a file PS10.DAT China.