Bart, I have done wat you said.
It's going a little better now.
question 1: Do I add the unit "interfaces" (in the uses clause) in all the Forms and also in all the units of the project?
question 2 : Does the unit "interfaces" the same as the unit "LCLintf"?
question 3 : Where can I set the name of the form which has to be the first form you see when the application starts?
greetings, Ton Smal, The Netherlands.