在文件A-Z中检测字母，然后AA-ZZ。

My question is a rather involved one.. I am trying to create a program that will read input from stdin (console) or from a file, it will then detect the number of occurrences of each letter and each letter pair, the output will go to a comma separated value (output.csv) file or a formatted text file (with option -c)My question is a rather involved one.. I am try