This article is just for them who don’t have any idea of what a pointer is, and does only describe it in the simple way.

Understanding pointers – for the amateurs
Written for all the beginners out there

This article is just for them who don’t have any idea of what a pointer is, and does only describe it in the simple way.

A pointer is like a web-address, it points to something: a record, an integer, a string, (...).

Many API functions have pointers as arguments, like the ShellExecuteEx function. It's delclared like this in the MAPI help file:

ShellExecuteEx(
LPSHELLEXECUTEINFO lpExecInfo // pointer to SHELLEXECUTEINFO structure
   );

To manage this, you find out what this structure if built up of:

typedef struct _SHELLEXECUTEINFO {   // sei  
    DWORD     cbSize;
    ULONG     fMask;
    HWND      hwnd;
    LPCSTR    lpVerb;
    LPCSTR    lpFile;
    LPCSTR    lpParameters;
    LPCSTR    lpDirectory;
    int       nShow;
    HINSTANCE hInstApp;

    // Optional members
    LPVOID lpIDList;
    LPCSTR lpClass;
    HKEY   hkeyClass;
    DWORD  dwHotKey;
    HANDLE hIcon;
    HANDLE hProcess;
} SHELLEXECUTEINFO, FAR *LPSHELLEXECUTEINFO;

Then, you assign values to the fields in a variable of this structure, and simly writes this:

ShellExecuteEx(@MyShellExecuteInfo);

An example from the internet: Instead of sending the great Delphi-page you found yesterday to a friend, you just send the web-address, so he can find it at the same place. That’s the principle of pointers. Not much, is it?

When you use pointers, you use two operators to tell what you mean: @ and ^. See the example under to see how.

If you who read this now CAN this, please write a comment, and explain more. I don’t know much more than I’ve just written!

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A short pointer example:
(To test this, choose File|New|Other|Console Application)

program UsePointer;

{$APPTYPE CONSOLE}

type
  MyPInteger = ^Integer; // This means: ‘MyPInteger’ is a pointer type to a Integer

var
  X: Integer;

procedure PrintOutInt(P: MyPInteger);

begin
  WriteLn(P^);  // Find the information at the address of P
  ReadLn; //Just to hang the program
end;

begin
  X := 17;
  PrintOutInt(@X); // Send the address of X as a parameter.
end.

Write ‘P1 := P2’ if you want to assign the memory address to another pointer.

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About this article and me: I’m still a beginner with Delphi – and I want to teach those who are at the same level as me what I know.

All the articles I’ve written till now is at the same level, and (I really hope!) easy to understand. Feel free to take a look at them too, and of course: I also want contact with Delphi programmers at my level (and age: 15). Hint, hint…
Martin Strand – marstr2@online.no (.no means Norway. I understand Norwegian, Swedish, Danish, English and some German.)