#include <MsgBoxConstants.au3>

Example()

Func Example()
        #cs Comments:
        Create the following structure (C language):
        struct {
                int var1;
                unsigned char var2;
                unsigned int var3;
                char var4[128];
        };

        Schema:
        ------------------------------------
        \ int    \ byte   \ uint   \ char   \
         \   var1 \   var2 \   var3 \   var4 \
          ------------------------------------
        #ce

        ; Assign a Local constant variable the definition of a structure (read carefully the DllStructCreate remarks).
        Local Const $tagSTRUCT1 = "struct;int var1;byte var2;uint var3;char var4[128];endstruct"

        ; Note: The tag variable is declared as Constant because its value will never change for any script execution.

        ; Assign a Local variable the structure.
        Local $tSTRUCT1 = DllStructCreate($tagSTRUCT1)

        ; If an error occurred display the error code and return False.
        If @error Then
                MsgBox($MB_SYSTEMMODAL, "", "Error in DllStructCreate, Code: " & @error)
                Return False
        EndIf

        ; Set the data of the element var1 (int) in the $tSTRUCT1.
        DllStructSetData($tSTRUCT1, "var1", -1) ; Or 1 instead of "var1".

        ; Set the data of the element var2 (byte) in the $tSTRUCT1.
        DllStructSetData($tSTRUCT1, 2, 255) ; Or "var2" instead of 2.

        ; Set the data of the element var3 (uint) in the $tSTRUCT1.
        DllStructSetData($tSTRUCT1, "var3", -1) ; The -1 (signed int) will be typecasted to unsigned int.
        ; Or 3 instead of "var3".

        ; Set the data of the element var4 (char) in the $tSTRUCT1.
        DllStructSetData($tSTRUCT1, "var4", "Hello") ; Or 4 instead of "var4".

        ; Note: This element can contain up to 128 characters.

        ; Change the data of the element var4 (char) in the $tSTRUCT1, at the index 1 of the char array (1 based index).
        DllStructSetData($tSTRUCT1, "var4", Asc("h"), 1)

        ; Display the results.
        MsgBox($MB_SYSTEMMODAL, "", "Struct Size: " & DllStructGetSize($tSTRUCT1) & @CRLF & _
                        "Struct pointer: " & DllStructGetPtr($tSTRUCT1) & @CRLF & _
                        "Data:" & @CRLF & _
                        DllStructGetData($tSTRUCT1, 1) & @CRLF & _ ; Or "var1" instead of 1.
                        DllStructGetData($tSTRUCT1, "var2") & @CRLF & _ ; Or 2 instead of "var2".
                        DllStructGetData($tSTRUCT1, 3) & @CRLF & _ ; Or "var3" instead of 3.
                        DllStructGetData($tSTRUCT1, 4)) ; Or "var4" instead of 4.

        ; Release the resources used by the structure.
        $tSTRUCT1 = 0
EndFunc   ;==>Example