1. A control system for regulating the operation of the components within a power plant feedwater system having various operating modes comprising means for selecting and monitoring the particular mode of operation existing at a specific time from a multiplicity of specific operating modes for the feedwater system, said particular operating mode being dependent upon the operating status of the components within the feedwater system, means for comparing measured feedwater system variables with corresponding predetermined system variables for said particular operating mode, said comparing means producing signals representative of the differences between said measured feedwater system variables and said correspondeing predetermined system variables for said particular operating mode, and means for producing control signals in response to said signals produced by said comparing means, said control signals being utilized to regulate the operation of the feedwater system components to control the flow of feedwater therethrough.