There is two possible meanings for string:
1) pointer to char to memory location starting textual information, generally pointers would be same size all
2) the actual text pointed by the pointer to char, which could be simple name or novel. Typically space would be reserved dynamically by malloc family functions.
By the way this kind of technical C++ question would be better placed in C++ forum, even you have no code samples.
For Each ctrl As Control In Me.Controls("pnlMainPanel").Controls
If ctrl.GetType Is GetType(System.Windows.Forms.Panel) Then
For Each subCtrl As Control In ctrl.Controls
If subCtrl.GetType Is GetType(System.Windows.Forms.TextBox) Then
If subCtrl.GetType Is ...