A method for programming a computer system having a display console for displaying images to control at least one of a virtual instrument and an instrument by the steps of displaying on the screen at least one first function-icon that references at least one first control module for controlling at least one first function; displaying on the screen at least one iteration-icon that references iteration control module for controlling multiple iterations of data flow; displaying on the screen at least one first input variable-icon that references at least one first input variable; displaying on the screen at least one first output variable-icon that references at least one first output variable; and assembling on the screen a first acyclic data flow diagram including the at least one first function-icon and the at least one iteration-icon and the at least one first input variable-icon and the at least one first output variable-icon, such that the diagram displays a first procedure for producing at least one value for the at least one first output variable-icon from at least one value for the at least one first input variable-icon, and such that the at least one iteration-icon in the diagram indicates multiple iterations of the at least one first function in the course of the first procedure.