All circuits fall into one of two well-known categories:
In a **combinational circuit**,
all circuit outputs are a strict *combination* of the current
circuit inputs, whereas in a **sequential circuit**,
some outputs may depend on past inputs (the *sequence* of
inputs over time).

The category of combinational circuits is the simpler of the two. Practitioners use three major techniques for summarizing the behavior of such circuits.

- logic circuits
- Boolean expressions, which allow an algebraic representation of how the circuit works
- truth tables, which list all possible input combinations and the corresponding outputs

Opening Combinational Analysis

Editing the truth table

Creating expressions

Generating a circuit