Excel Home Delphi 3 and Automation with Excel.
Automation allows one application to control another application.
The application controlling the server is called an automation controller. When using this method, function names and parameter datatypes are resolved at runtime, all parameters are passed as variants. As no errors in function names or parameter types are reported at compile time, this method is error prone. As function names and parameter types need to be looked up at runtime, performance is slow. The only advantage of this method for Delphi programming is that it is the only way optional parameters can be omitted from function calls.