... Dec(Var I : Longint;decrement : Longint); Dec(Var I : Longint); Dec(Var I : Byte;decrement : Longint); Dec(Var I : Byte); ...When the compiler encounters a call to the dec function, it wil first search which function it should use. It therefore checks the parameters in your function call, and looks if there is a function definition which maches the specified parameter list. If the compiler finds such a function, a call is inserted to that function. If no such function is found, a compiler error is generated. You cannot have overloaded functions that have a cdecl or export modifier (Technically, because these two modifiers prevent the mangling of the function name by the compiler)