An expandable modular control system with reduced memory requirements comprising an electronic data processing (EDP) system employing a microprocessor device and having gated program interrupt means. In particular, the expandable modular control system of the present invention comprises a "universal" microprocessor module which can be selectively combined with other separately packaged peripheral support modules to implement any particular control system required. Control point modules comprising a matrix array of flip-flops arranged as a plurality of n-bit words and subject to program control serve as extensions of the memory module to control the states of corresponding points in the system under the control of the modular control system. Sense point modules similarly organized in a matrix array monitor or sense the status of the points in the system under control and provide input data to the microprocessor module. Since the status of the C,Z,S and P flag bits cannot be restored the gated interrupt means also included selectively gate waiting program interrupts, if any, to the microprocessor coincident with a "gate interrupt" instruction in the program being executed so that a subroutine can be executed before the program is resumed thereby enabling the microprocessor to function as a virtually interruptable CPU.