A control system for a machine comprising a plurality of independently replaceable machine modules comprises a controller operable to control operation of the machine. Memory stores machine data for use by the controller. Communication means are operable to provide communication for data transfer between the controller and the memory. The memory includes a plurality of memory modules associated with respective machine modules. Each of the memory modules is replaceable with the respective associated machine module and independently of other memory modules. The communication means is operable to provide communication for data transfer between the controller and a replacement memory module associated with a replacement machine module.