I have a string of utf_8 Farsi characters , which are supposed to be
converted to iran System char map. As in iran system lower case and
upper case characters differ from each other, I need to read my string
chars in a way that lower case and upper case chars are detectable.

As you know using substring function , the result is always upper case.
I took a look at farsido editor, but it didnot worked correctly.

I would appriciate your help if you solve my problem.