Basic information on building digital circuits for metal-oxide-semiconductor (MOS) transistors is presented. The structure, principle of operation, current-voltage characteristics and equivalent circuits of MOSFETs are considered. The basics of logic algebra, logic elements and combinational digital circuits are presented: inverter, "NOR," "NOR," "NOR," "NOR," "exclusive OR," "exclusive NOR," multiplexers and adders. Implementation of circuits using transistors with additional control on drain or source is described. Sequence digital circuits are given - triggers, registers and counters.