The 74154 is a 1-of-16 decoder. It accepts a 4-bit binary input.

Exclusive-AND gates are needed for conversions between Gray code and binary code.

In a priority encoder, the input with the highest priority is represented on the output.

The basic comparator evaluates two binary strings bit by bit and always outputs a 1.

The digit bus and display bus are each just a common set of conductors shared by the digit storage registers and display segments.