This paper describes the working of the APACHE (Analog Programing And CHEcking) system for the production of analog computer programs using a digital computer, which has been developed jointly by digital and analog programers at the computation center of EURATOM in Ispra, Italy. The language which has been formulated for the writing of analog problems is discussed and its rules are set out in the Appendix, while the processes involved in the utilization of the program are described and illustrated by an example of the listing of the digital computer input and output for a range of equation types. Finally, the significance of this new programing system in terms of economic exploitation of the analog machine, the use of trained personnel, and the design of new computers, are considered briefly.