Ok, let me see if I can explain clearly.

"the place where you write store the characters" is, for example:

In MS word you use a textbox.
In a small C++ application you store strings (character arrays) in a char * variable.

But the variables are limited to a 255 characters capacity. So where should I store the stuff the user writes before saving?

It's not the world you live in, it's the people you live with.