Abstract: An apparatus for detecting and correcting errors in the arithmetic processing of data represented in the numerical system of residual classes comprises a register coupled to a residue calculator, a control unit coupled to a constant storage unit which connects an error syndrome calculator, a comparator coupled to an error syndrome calculator. A modulo adder is connected to the register and to the residue calculator whereas single and multiple error detectors are coupled to the register and to the residue calculator via a first group of AND gates and are also coupled to a group of OR gates and to an analyzing unit via a group of OR gates. The analyzing unit connects second and third groups of AND gates as well as a second output bus and a logic unit coupled to an adder which is connected to a first output bus. Coupled to the adder are a fourth group of AND gates, a control flip-flop and the register. The second group of AND gates is coupled to an OR gate and to the constant storage unit.