Various embodiments are described in which different irrigation controllers in an irrigation control system have machine code having a same code base. In one implementation, a first irrigation control unit comprises a processor and a medium storing a first set of machine code to be executed by the processor. The first set is based on a portion of source code on which a second set of machine code stored in a second irrigation control unit is based, and the first and second sets not identical to each other. The first and second irrigation control units are in a predefined hierarchical control relationship. In one variation, the first and second control units have at least related operating systems. In another variation, a central controller includes machine code developed from at least a portion of the same source code as machine code in a remote controller for simulation or execution purposes.