Special Output Gates

It is sometimes desirable to have a logic gate that provides both inverted and non-inverted outputs.
For example, a single-input gate that is both a buffer and an inverter, with a separate output terminal
for each function.

Or, a two-input gate that provides both the AND and the NAND functions in a single circuit. Such gates do exist and they are referred to as complementary output gates. The general symbology for such a gate is the basic gate figure with a bar and two output lines protruding from it. An array of complementary gate symbols is shown in the following illustration:

Complementary gates are especially useful in "crowded" circuits where there may not be enough
physical room to mount the additional integrated circuit chips necessary to provide both inverted
and noninverted outputs using standard gates and additional inverters.