Merge pull request arduino#240 from arduino/variable-type

Changing the data type in function

Author: Stefania

Language/Variables/Data Types/String/Functions/charAt.adoc

@@ -34,7 +34,7 @@ string.charAt(n)
 === Parameters
 `string`: a variable of type String
 
-`n`: a variable of type int
+`n`: a variable of type unsigned int
 
 
 [float]