APPARATUS AND METHOD ENABLING A COMPUTER TO TRANSFER CONTROL BETWEEN TWO PROGRAM SEGMENTS THAT CALL ONE ANOTHER BUT OPERATE IN DIFFERENT MODES

A software product and method for operating a computer, so that a first program operating in a first operating mode having a first addressing format may call code located in a second program operating in a second operating mode having a second addressing format. An argument converter converts all arguments in a stack used in inter-process communication from the first addressing format to the second addressing format. A call gate converts the desired return address into the second addressing format. Thus the called second program properly recognizes the received data and upon completion generates the correct return address.