Setting up the Delphi Environment

I think it is important the DLLs I write can be called from any language. This basically means following the C style. (This is most important with strings, see later). Therefore I use Delphi as a prototyping tool for VB so I can do all the development and testing in Delphi. When I create the DLL and test from VB, I know the code is working OK.

Step 1: I create a Delphi project in the normal way, say rg.dpr. In this project I create a form and add buttons. Under the button.click event I put code to test the procedure being created. All the code to be included in the DLL is put into other units. Therefore, the smallest application has four files.

I then create another project, say rgdll.dpr, using the following method:

1. Close all existing projects and units.
2. Create a new project with menu File/New Project
3. Remove form1 using menu View/Project Manager,delete unit
4. Add units containing the DLL code using menu File/Add File
5. Display project file using menu View/Project Source and then edit the project file to set declarations for creating the DLL.

The new project file, with the changes shown, is below:

  library Rgdll;              {*1.program changed to library}
  uses                        {*2.removed Forms }
    Rg2 in 'RG2.PAS';         {$R *.RES}
  exports                     {*3.add exports clause and the}
      ChangeInt,              {functions and procedures to export}
      ChangeSingle;
  begin                       {*4.remove code from main block}
  end.

Therefore, the smallest DLL project has 2 files:

  rgdll.dpr.   the project file
  rg2.pas      the unit file(s) with DLL code

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