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Hello Autoit, I'm very new to DllCall function, in fact never used it, but I'm just curious about it. I found @toasterking's awesome beginner friendly dll GUI: I searched for some easier functions (less input / less output parameters), and I found GetFileSize function (I didn't modify his code, just using the GUI): https://learn.microsoft.com/en-gb/windows/win32/api/fileapi/nf-fileapi-getfilesize So, this is what I did: The function itself is executing like this, but the output is 0 and -1 DllCall("kernel32.dll","int","GetFileSize","HANDLE","D:\DllCall GetFileSize Example.au3","DWORD*","$hello") Then, I tried to execute my script (very simple) and put it into D drive: ;DllCall("kernel32.dll", "int", "GetFileSize", "HANDLE", "D:\DllCall GetFileSize Example.au3") $aDllCallReturn = DllCall("kernel32.dll","int","GetFileSize","HANDLE","D:\DllCall GetFileSize Example.au3","DWORD*","$hello") For $i = 0 To UBound($aDllCallReturn) - 1 ConsoleWrite($i & ": " & $aDllCallReturn[$i] & @CRLF) ;MsgBox(0, $i, $aDllCallReturn[$i]) Next ;ConsoleWrite($hello & @CRLF) The result is as the following (same as the screenshot): 0: -1 1: 0x00000000 2: 0 This file size is 403 bytes in my computer, it's very small, I expected to see 403 somewhere, but I don't know where I made it wrong. So, now I have some questions: 1. Do I really need to use lpFileSizeHigh or can I use "hello"? 2. Do I always have to put $ in the beginning of the parameter? I tried without $ in his GUI, I got an error. So, I think $ is a must. 3. But if I write as $hello (expecting this will store the file size), when I ConsoleWrite it, Autoit becomes angry because "undeclared global variable". 4. If somehow $hello will be the output to my file size, why do I need to return an array $aDllCallReturn which contains 3 elements? So, I have one $hello + 3 items from the array = I have 4 outputs total. But Microsoft says this function has only one return "[out, optional] LPDWORD lpFileSizeHigh ". I'm confused. Please note that; the goal for me is to use the DllCall function, not to get the file size by using FileGetSize() or some other existing functions.

AutoIt is very useful and easy to use even for non-programmers (like me). Most of the examples in the Example section of the forum are somewhat advanced and not suitable for non-programmers who want to learn how to do simple things with AutoIt. I've attached a few simple scripts with lots of comments to help beginners. For more help on any function, press F1 when your curser is on the desired function name. Example01_MouseSwitchButtons.au3 Example02_HelloWorld.au3 Example03_CopyPasteNotepadToWord.au3 Example04_CopyPasteNotepadToWord_2.au3 Example05_OpenLinkInIE.au3 Additional simple AutoIt examples can be downloaded from here: '?do=embed' frameborder='0' data-embedContent>> P.S. Can somebody pin this topic?