1. In a computing system, a method of preparing a computer program for operation in a computer supply system that supplies portions of program code or program data of the computer program as the program needs the portions, the portions identified as program units, the method comprising: defining a program unit of the program; removing the program unit from the program, thereby producing a program skeleton that is missing the program unit; and inserting instructions in place of the program unit in the program skeleton, the instructions operative to request the program unit when the program skeleton encounters the instructions.