Truth Tables

A truth table is a structured way of showing all possible input combinations for a logic gate or circuit and the resulting outputs. Truth tables are a fundamental tool in GCSE Computer Science — you must be able to read, complete and construct them.

---

What Is a Truth Table?

A truth table is a table that lists:

1. Every possible combination of input values (0s and 1s).
2. The output for each combination, according to the logic gate(s) or Boolean expression being evaluated.

Truth tables allow us to see the complete behaviour of a logic system at a glance.

---

How Many Rows?

The number of rows in a truth table depends on the number of inputs. For n inputs, there are 2^n (2 to the power of n) possible combinations:

Number of Inputs	Number of Rows (2^n)
1	2
2	4
3	8
4	16