Demultiplexors - used to switch a single input to one of many outputs

Equality detector - 4-bit words, output is high if they are equal. XNOR implementation.

BCD validity detector - output F is a flag bit that indicates inputs are non-BCD codes. Kmap implementation

Binary adders: full adder

• binary addition by hand
• full-adder truth table
• expressions for S and Cout
• half-adder
• full-adder constructed from 2 half-adders